
==== Front
Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

39232017
65783
10.1038/s41598-024-65783-x
Article
CTAB-crafted ZnO nanostructures for environmental remediation and pathogen control
Gaur Jyoti 1
Kumar Sanjeev kumarsanju25@gmail.com

2
Zineddine Mhamed z5868@yahoo.com

3
Kaur Harpreet 2
Pal Mohinder 1
Bala Kanchan 4
Kumar Vanish 5
Lotey Gurmeet Singh 6
Musa Mustapha 3
El Outassi Omar 7
1 School of Basic and Applied Sciences, RIMT University, Mandi Gobindgarh, 147301 India
2 https://ror.org/05t4pvx35 grid.448792.4 0000 0004 4678 9721 Department of Physics, Chandigarh University, Gharuan Mohali, 140413 India
3 grid.499278.9 0000 0004 7475 1982 EUROMED University of Fez, 3000 Fez, Morocco
4 Department of Chemistry, Government Mohindra College, Patiala, 147001 Punjab India
5 https://ror.org/05nnsek89 grid.452674.6 0000 0004 1757 6145 National Agri-Food Biotechnology Institute (NABI), Sector 81, SAS Nagar, Mohali, 140306 Punjab India
6 https://ror.org/05gxnyn08 grid.257413.6 0000 0001 2287 3919 Department of Physics, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, IN 46202 USA
7 grid.10412.36 0000 0001 2303 077X Materials and Modelling Laboratory, Department of Physics Faculty of Sciences Meknes, Moulay Ismail University, Meknes, Morocco
4 9 2024
4 9 2024
2024
14 2056128 2 2024
24 6 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
This study addresses the critical need for efficient and sustainable methods to tackle organic pollutants and microbial contamination in water. The present work aim was to investigate the potential of multi-structured zinc oxide nanoparticles (ZnO NPs) for the combined photocatalytic degradation of organic pollutants and antimicrobial activity. A unique fusion of precipitation-cum-hydrothermal approaches was precisely employed to synthesize the ZnO NPs, resulting in remarkable outcomes. The synthesized CTAB/ZnO NPs demonstrated exceptional properties: they were multi-structured and crystalline with a size of 40 nm and possessed a narrow band gap energy of 2.82 eV, enhancing light absorption for photocatalysis. These nanoparticles achieved an impressive degradation efficiency of 91.75% for Reactive Blue-81 dye within 105 min under UV irradiation. Furthermore, their photocatalytic performance metrics were outstanding, including a quantum yield of 1.73 × 10–4 Φ, a kinetic reaction rate of 3.89 × 102 µmol g–1 h–1, a space–time yield of 8.64 × 10–6 molecules photon–1 mg–1, and a figure-of-merit of 1.03 × 10–9 mol L J–1 g–1 h–1. Notably, the energy consumption was low at 1.73 × 10–4 J mol–1, compared to other systems. Additionally, the ZnO NPs exhibited effective antimicrobial activity against S. aureus and P. aeruginosa. This research underscores the potential of tailored ZnO NPs as a versatile solution for addressing both organic pollution and microbial contamination in water treatment processes. The low energy consumption further enhances its attractiveness as a sustainable solution.

Keywords

ZnO nanoparticles
CTAB
Photocatalysis
Antimicrobial activity
Wastewater treatment
Multi-functionality
Subject terms

Pollution remediation
Nanoscale materials
issue-copyright-statement© Springer Nature Limited 2024
==== Body
pmcIntroduction

The continuously increasing industrial discharge into lakes, oceans, rivers, and other water bodies severely affected the environment health1,2. It should be noted that pollutants like heavy metals, dyes, pesticides, and industrial and pharmaceutical waste are very common in wastewater. These pollutants may or may not be directly toxic; however, a few of them can produce hazardous by-products through diverse processes, e.g., hydrolysis, chemical reactions, and oxidation. The above-mentioned processes is suspected to increase the chemical oxygen demand (COD) and biological oxygen demand (BOD), which is threatening not only for the environment (e.g., for microorganisms, plants, animals, and aquatic life)3–5.In particular, the increased use of dyes in several industries (e.g., textiles, plastic, leather, medical, automobiles, and paper industries) has contributed significantly to the environmental degradation6–8. In recent years, rapid progress has been made in the dye business. Interestingly, as per United States Colour Index, till now tens of thousands commercial dyes have been reported. The world's annual dye waste is > 60,000 tonnes and ~ 80% of which consist of azo dyes9. Notably, a few of azo dyes and their metabolites are toxic and carcinogenic in nature. In general, the textile effluent can have 10–800 mg L−1 of dyes, which may vary from factory to factory10. Thus, the treatment of wastewater or pollutant containing water is necessary to make our environment healthy. Till now several research efforts have been put forward to develop efficient pollutant removal system. Most of the developed pollutants (especially organic pollutants) removal techniques can be categorized in chemical, physical, and biological techniques. The mythology behind these techniques can include sedimentation, ultrafiltration, adsorption, ion exchange chemical oxidation, anaerobic, photocatalytic, and reverse osmosis11–13.However, some of the above-said techniques are associated with limitations such as costly equipment, operational problems, secondary waste generation, low degradation efficiency, and slow process14. Consequently, advanced oxidation processes such as photocatalysis, and ultraviolet treatment are introduced as progressive treatment techniques for the removal/ degradation of organic dyes. Among them, photocatalysis one of the best, most explored, and cost-effective process to remove dyes15.

A paradigm shift has been observed in the photocatalysis process after the inception of nanomaterials. Till now, a wide variety of nanomaterials have been tested for the removal of diverse hazardous dyes16–18. A good number of semiconductor materials-based photocatalysts, e.g., TiO2, SnO2, Bi2O3, CdS, CdSe, WO3, and ZnO, have been investigated for the removal of organic pollutants from the water. Out of above-mentioned photocatalytic materials, nanometer-sized ZnO is of special interest to the scientific community and researchers because of their high exciton binding energy (60 meV), wide direct band-gap (3.37 eV), non-toxicity, long-term stability, cheap cost, and high electron mobility19,20. ZnO NPs are an efficient and promising material for the photocatalytic degradation of industrial dyes due to their high efficiency, biocompatibility, cheap manufacturing cost, and improved control of physicochemical parameters. On the other hand, ZnO nanoparticles are becoming increasingly popular among researchers due to its anti-microbial properties. In particular, the physicochemical properties of ZnO NPs make them a promising material for photocatalytic and anti-microbial applications.

Till now, a good number of synthesis techniques have been explored effectively to create and modify ZnO nanostructures, including hydrothermal, solvothermal, hydrolysis, sol–gel, co-precipitation, thermal decomposition, microwave, and solid-state reaction methods21–24.Among all these methods, the hydrothermal and chemical precipitation methods are found to be the most convenient as these offer various advantages, such as low-temperature processing, cost-effectiveness, easy adoptability, and the ability to produce in large quantities. Moreover, one can easily control the characteristics of obtained nanomaterials via altering the reaction conditions (such as reaction temperature, solvent, surfactant and precursors) in hydrothermal and chemical precipitation methods25.

Herein we report an effective strategy to synthesized multi-structured ZnO functionalized with CTAB through a streamlined precipitation-cum-hydrothermal process, marking a novel approach in the facile and one-pot fabrication of distinctive nanostructured ZnO, which demonstrated exceptional efficacy in the efficient degradation of industrial reactive blue-81 (RB-81) dye26–29. Beyond its prowess in organic molecule removal, these fabricated structures exhibited remarkable antimicrobial activity against two bacterial species, namely Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). Our research highlights the successful achievement of multi-structured ZnO, showcasing extraordinary capabilities in both organic pollutant removal and antibacterial lethality. Importantly, we quantified key performance parameters, including quantum yield (QY), kinetic reaction rate, space–time yield (STY), and figure-of-merit (FOM), and conducted a comparative analysis with recent studies in the field. The results indicate that our developed multi-structured ZnO material outperforms its counterparts, emphasizing its significant contributions to advanced catalytic systems.

Materials and methods

Materials

Zinc acetate dihydrate ((CH3COO)2Zn.2H2O: ≥ 98% purity), sodium hydroxide (NaOH: ≥ 98% purity), ethanol (CH3CH2OH: ≥ 99.9% purity), and N-cetyl-N, N, N-trimethyl ammonium bromide (C19H42BrN, ≥ 99% purity) were purchased from Sigma-Aldrich (St. Louis, Missouri, United States of America (USA)). All the above-mentioned chemicals were of analytical reagent (AR) grade and used as received without any further purification. The RB-81 dye (C25H14Cl2N7Na3O10S3.3Na) was procured from Parshwanath Dyestuff Industries, Ahmedabad, India. During the synthesis of ZnO NPs, distilled water (DW) and filter papers (grade 41, pore size 20 m, Whatman, England) were used.

Synthesis of CTAB-assisted ZnO

In this study, CTAB-assisted ZnO NPs were synthesized via a unique chemical precipitation-cum-hydrothermal method (Fig. 1). In addition, the CTAB-assisted ZnO nanoparticle synthesis method has been successfully optimized to achieve high yields through systematic investigation of various parameters. These parameters include: precursor concentration ((CH3COO)2Zn∙2H2O and CTAB), temperature (focusing on hydrothermal treatment), pH, and reaction times.Figure 1 Schematic illustration of the precipitation-cum-hydrothermal technique for the synthesis of CTAB/ZnO.

In a typical experiment process, Zn(CH3CO2)2 (0.2 M, 3.5118 g) was added to the distilled water (50 mL) and stirred for 20 min. Then CTAB 30 mL (0.01 M) was added to the afore-prepared solution and stirred for another 15 min at a temperature of 60–70 °C. The pH of the solution was set to 8 and the solution was further stirred for an hour to achieve precipitation of the desired nanoparticles. Afterwards, the obtained solution was transferred to an autoclave and placed into a vacuum oven (temperature: 200 °C, time: 4 h). After that, the autoclave was allowed to cool down to room temperature. The precipitates were filtered and washed with distilled-water/ethanol repeatedly to remove any impurities. The precipitates were dried (temperature: 80 °C, time: 4 h) and crushed to obtain a fine powder of CTAB/ZnO. The synthesized particles were stored at dry and dark place for further characterizations and applications. During synthesis, CTAB is highly effective at stabilizing nanoparticles. Its amphiphilic nature, with a hydrophilic ammonium head and a hydrophobic cetyl tail, allows it to adsorb onto the nanoparticle surface and create a steric barrier. This barrier prevents agglomeration and ensures a stable dispersion of nanoparticles in the solution. Other capping agents might not provide the same level of stabilization, leading to larger or aggregated particles30. In addition, CTAB is superior due to its effective stabilization, controlled morphology, compatibility with various synthesis methods, enhanced solubility and dispersion, surface functionalization, and cost-effectiveness, leading to uniform, well-defined nanoparticles and making it ideal for large-scale synthesis.

Characterization techniques

The synthesized particles were characterized by X-ray diffractometer (X'Pert PRO, PANalytical, Japan) to know the interplanar spacing (dhkl) among adjacent planes, Miller indices (h k l), crystallite sizes (D), and crystallite phases. The absorption band edge and electrical band gap energy (Eg) of ZnO NPs were examined using a UV–visible (UV–vis) spectrophotometer (UV-2600, Shimadzu, Japan). A field emission scanning electron microscope (FE-SEM; SUPRA 55-VP, Carl Zeiss, Germany) was used to record the size, shape, aggregation, agglomeration, and uniformity of particle distribution. The high-resolution transmission electron microscopy (HR-TEM; JEM-2100, JEOL, Japan) was used for the investigation of particle size distribution, shape, lattice parameters, and interplanar spacing for distinct planes of ZnO NPs. The elemental composition and functionality on synthesized ZnO NPs were confirmed by energy-dispersive X-ray (EDX) spectrometer (AZtec, Oxford, America) and Fourier-transform infrared (FTIR) spectrometer (Alpha II, Bruker, Germany), respectively. Moreover, the chemical state of ZnO was analyzed using X-ray photoelectron spectroscopy (XPS: PHI 5000 VersaProbe II, ULVAC-PHI, Inc., Japan).

Dye degradation studies using CTAB/ZnO

In current study, the effectiveness of the CTAB/ZnO has been evaluated on the RB-81 dye. The chemical composition of RB-81 dye is shown in Fig. 2a. The photocatalytic dye degradation experiment has been conducted on a DW solution of 120 mg L−1 of RB-81 dye. To initiate the dye degradation experiment, 150 mg L−1 or 200 mg L−1 photocatalyst was ultrasonically disseminated in the RB-81 dye solution. To achieve the adsorption–desorption equilibrium, the suspension of ZnO nanomaterial and dye was stirred continuously while kept in the dark for sixty minutes. Following this, the suspension was moved to a photoreactor equipped with a UV (6 W) lamp (λmax = 254 nm) Fig. 2b. After that, the suspension was irradiated with UV light for varying amounts of time (for example, 0–105 min) with continuous stirring. The dye degradation performance of the photocatalyst was monitored after every 10 min. Note that the photocatalyst was removed via centrifugation before measuring the absorbance of the testing solution. Equation (1) was used to perform the analysis necessary to determine the photocatalytic activity31.1 A=(E0-Et)/A0×100

Figure 2 Schematic illustration of the RB-81 dye and the experimental set-up for dye degradation: (a) chemical structure of RB-81, and (b) photoreactor along with various components.

The dye absorbance (λmax: 583 nm) is denoted by the symbols E0 and Et at time = 0 and t min of UV exposure, respectively.

To conduct a control experiment, the RB-81 dye solution was subjected to UV light in absence of photocatalyst. The schematic of the photoreactor used in current study is shown in Fig. 2b.

Importantly, the performance of the CTAB/ZnO photocatalytic on dye degradation was evaluated on four key performance metrics (1) QY (Eq. 2), (2) Photon flux (Eq. 3), (3) STY (Eq. 4), and (4) FOM (Eq. 5)32. In particular, the capability of photocatalyst to efficiently use the light energy can be estimated using QY. Likewise, the photocatalyst mass-based QY can be measured using STY, while the FOM gives a numerical description of the photocatalytic system that can be used on the industrial scale (by including energy consumption, time, catalyst mass, and product obtained into calculation)32,33.2 QY=DecayRatemoleculepersecondPhotonfluxphotonpersecond

3 Photonflux=photon/Sec∗Irradiationtime

4 STY=QYPhotocatalystmassmg

5 Figureofmerit=ProductobtainedLCatalystmassg×Timeh×EnergyconsumptionWhμmol

Experimental design for antimicrobial test

The inhibitory effects of an aseptic ZnO solution on bacterial growth have also been investigated. The antibacterial properties of synthesized ZnO material were tested on gram-positive (e.g., S. aureus) and gram-negative bacteria (e.g., P. aeruginosa). The culture plates (3 mm deep) were kept at 35 °C for 18 h to simulate the optimal growth conditions for bacteria. The antibacterial potential of ZnO solution was examined by exposing bacteria to 10, 25, and 40 μL of ZnO solution. At the end of experiment, the centimetre-scale measurements of the inhibitory regions were taken to determine the extent of bacterial growth inhibition.

Results and discussion

Structural analysis of CTAB/ZnO via powder X-ray diffraction (PXRD)

The phase structure analysis of the synthesized ZnO was conducted using powder X-ray diffraction (PXRD), a swift analytical technique widely employed for the phase identification of crystalline materials and the determination of unit cell dimensions. The XRD pattern of the CTAB-loaded ZnO developed in this study is presented in Fig. 3. The data were collected within the range of 30°–70° (2θ), as shown in Fig. 3a. Figure 3a displays the Rietveld profile fitting for CTAB/ZnO NPs. The quality of this fitting was thoroughly assessed using the goodness of fit parameter (Chi2 = 5.75). This statistical metric confirms that the theoretical model is in good agreement with the experimental results. During the analytical process, several parameters were modified, such as the background function, scale factors, profile functions, peak width parameters (u, v, w), and lattice parameters. These modifications are essential for optimising the alignment between the theoretical and actual XRD profiles, resulting in a more precise depiction of the crystal structure. The crystallinity of the ZnO nanostructure was clearly discerned in the XRD pattern, indicated by sharp peaks at specific 2θ values, such as 31.66°, 34.32°, 36.16°, 47.46°, 56.52°, 62.80°, 66.32°, 67.88°, and 69.00°, corresponding to the lattice planes (h k l) of (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0), (1 0 3), (2 0 0), (1 1 2), and (2 0 1), respectively34. The diffraction pattern of the ZnO nanostructure was indexed to the hexagonal wurtzite crystal structure, as this result is in good agreement with the previous reports35. This analysis underscores the crystalline nature and structural integrity of the developed ZnO, providing valuable insights into its potential applications. The diffraction pattern of the ZnO nanostructure was indexed to the hexagonal wurtzite crystal structure, as this result is in good agreement with the previous reports35. In the earlier study, the structure of ZnO was described as several alternating planes composed of tetrahedrally coordinated O2− and Zn2+ ions, stacked alternately along the c-axis36. In another investigation, the XRD spectrum of Ni-doped ZnO NPs synthesized by the chemical co-precipitation method confirmed the single phase with a hexagonal wurtzite structure with space group P63mc.Figure 3 X-ray diffraction spectrum of CTAB/ZnO powder: (a) Rietveld analysis, (b) standard ZnO, (c) W–H plot, and (d) and Modified Debye–Scherrer plot.

The average grain size and structural parameters of the synthesized ZnO were calculated using Debye–Scherrer’s formula37.6 D=Kλ/βcosθ

where D is the average crystallite size in Å, K is the shape factor (0.9), λ is the wavelength of X-ray, β is full-width at half-maximum intensity (FWHM), and θ is the Bragg’s angle. Inter-planar spacing between planes in the atomic lattice for each diffraction peak was calculated using Bragg’s law.7 2dsinθ=nλ

where d is the inter-planar spacing.

The structural and geometric parameters (e.g., FWHM, lattice planes, d, and D) are illustrated in Table 1. The average crystallite size of synthesized ZnO NPs is ~ 28.22 nm. Based on highest peak (101) in XRD, the crystalline size was calculated as 32.24 nm. The deviation between the average size calculated from the maximum peak and average size suggested the presence of differentially shaped ZnO38. The Rietveld evaluation confirms that the positions and strengths of the diffraction peaks in the XRD spectrum of the nanoparticles are in line with the expected diffraction patterns of a hexagonal wurtzite crystal structure CTAB/ZnO with space group P63mc and specific cell parameters (a = b = 2.8100 and c = 5.2200 Å, and V = 35.73 Å3). The validity of this information is supported by the JCPDS card number 00-079-2205, as seen in Fig. 4(b) and elaborated upon in Table 1.Table 1 Basic crystallographic parameters of CTAB/ZnO NPs.

(A) Structural and geometrical parameters		
Order	2θ (degree)	FWHM (β)	Lattice planes	Inter-planner spacing (d) (Ao)	Crystallite Size (D) (nm)		
1	31.66	0.26236	(100)	2.82385	32.87		
2	34.32	0.26110	(002)	2.61082	33.26		
3	36.16	0.27074	(101)	2.48208	32.24		
4	47.46	0.30943	(102)	1.91414	29.29		
5	56.52	0.33818	(110)	1.62691	27.86		
6	62.8	0.37122	(103)	1.47848	26.19		
7	66.32	0.41807	(200)	1.40828	23.71		
8	67.88	0.40819	(112)	1.37966	24.50		
9	69	0.41874	(201)	1.35998	24.04		
				Average crystallite size = 28.22		
(B) Lattice parameters and unit cell volume of CTAB/ ZnO	
Order	Lattice constants	Standard values (Ao)	Calculated values (Ao)	c/a ratio	Standard volume (Ao)3	Calculated volume (Ao)3	
1	a = b	3.2501	2.8100	1.85	47.61	35.73	
2	c	5.2071	5.2200	

Figure 4 UV–vis energy band gap plots of CTAB/ZnO NPs: (a) UV–vis absorption spectrum and (b) Tauc’s plot.

The FWHM for all marked peaks was calculated using Lorentz curve fitting (R2 > 0.99). Interplanar-spacing values of dexperimental = 2.482 Å and dbulk = 2.481 Å (JCDPS card number #00-036-1451) for the longest peak (101) showed that the synthesised ZnO NPs crystallites were free of contaminants and crystallographic irregularities. It is worth noting that differences in d-space values between materials (photocatalysts) can result in different mass densities and electronic band structures. As a result, photocatalysts' absorption of light at specific energies alters their ability to degrade pollutants39. The absence of irregularities between synthesized and standard ZnO’s d-space values indicates the unchanged positions of Zn and O within the crystal structure. Furthermore, the considerably large peak intensities in the XRD spectrum (Fig. 3a) represent that the prepared ZnO's phase evolved properly. Additionally, the prepared ZnO demonstrates a high degree of crystallinity, as evidenced by the sharp peaks in the XRD spectrum40. Interestingly, we did not notice any diffraction peaks corresponding to Zn, Zn(OH)2, or other ZnO phases, which indicate that pure ZnO with a hexagonal wurtzite phase was formed. The interaction of the zinc cluster and surfactant CTAB results in a chemical reaction in which the zinc cluster undergoes intense oxidation, resulting in the formation of Zn(OH)2, which thermally decomposes into ZnO41.8 Zncluster+H2O→ZnOH2

9 ZnOH2→ZnO+H2O

The CTAB/ZnO unit cell volume (35.73 Ao) differs significantly from the bulk ZnO volume (47.61 Å) (Table 1), indicating the existence of internal stresses. It was reported earlier that the analysis of the peak broadening in XRD can reveal the crystallite size as well as the internal stress of the nanocrystals. The Williamson–Hall (W–H) method was utilized to determine the relationship between the peak broadening in diffraction peaks and the nanocrystals’ internal stress, and crystallite size. Unlike the Scherrer equation, which is 1/cosθ dependent, the W–H technique is tanθ dependent42. The W–H plot between 4sinθ and βT cosθ is shown in Fig. 3c. Equation (10) was used to compute the crystallite size from the plot.10 βTcosθ=∈4sinθ+KλD

Here βT denotes the overall expansion.

The W–H plot revealed a crystallite size of 44.00 nm with a strain (ε) value of + 3.15 × 10–3. The existence of tensile stress is indicated mostly by the positive value of internal strain. The lattice characteristics and unit cell volume of the CTAB/ZnO are also included in Table 1. To get a more precise estimate of the crystallite size, it is possible to compute the systematic error in the Scherrer formula by subtracting the errors from the individual peaks43. Ln(1/cosθ) vs Lnβ is shown in Fig. 3d, also known as the Monshi (Modified Debye–Scherrer) plot. From this figure, the crystallite size was determined using Eq. (11) as follows:11 Lnβ=1Ln1Cosθ+LnKλD

Here the intercept of a least-squares regression (ln = Kλ/D) was used to figure out the sizes of the crystallites for each XRD peak. Table 2 lists the different lattice parameters estimated from the W–H and modified Debye–Scherrer plots. Based on the modified Debye-Scherer approach, the average crystallite size of CTAB/ZnO was determined to be 33.14 nm. The analysis of the crystallite size of CTAB/ZnO computed by various approaches yielded significantly distinct findings (Table 2). Small crystallite size CTAB/ZnO NPs may activate the ZnO surface for improved dye adsorption and photocatalytic activity.Table 2 Basic crystallographic parameters of CTAB/ZnO NPs calculated using W–H and Modified Debye–Scherrer equations.

(A) Structural and geometrical parameters	
Order	2θ (degree)	FWHM (β)	βT cos θ	4 sin θ	Ln (1/cos θ)	Lnβ	
1	31.65456	0.2666	0.004476643	1.09095341	0.038649102	− 5.370232836	
2	34.32051	0.26251	0.004377703	1.18018128	0.045538036	− 5.385693067	
3	36.14647	0.27956	0.004638504	1.2409295	0.050598003	− 5.322765305	
4	47.45205	0.30528	0.004877806	1.6094546	0.088306843	− 5.234752856	
5	56.51112	0.34431	0.005293299	1.89362059	0.126873829	− 5.11443983	
6	62.79184	0.36729	0.005471857	2.0837954	0.158306759	− 5.049830517	
7	67.88695	0.40289	0.005833467	2.23349899	0.186825075	− 4.957318672	
8	69.01706	0.39285	0.005650064	2.26611569	0.193533956	− 4.982554384	
(B) Crystallite sizes by different methods				
	Computational methods	The crystallite size (nm)					
1	Debye–Scherrer’s equation	28.22					
2	Williamson-Hall equation	44.00					
3	Modified Debye–Scherrer’s equation	33.14					

The PXRD analysis highlights the successful synthesis of highly crystalline, pure ZnO nanoparticles with a hexagonal wurtzite structure. The detailed structural parameters obtained provide a solid foundation for further exploring the material’s applications in areas such as environmental remediation, sensor technology, and optoelectronics.

Analysis of the optical properties of CTAB/ZnO using UV–visible spectroscopy

The optical and electrical characteristics of semiconducting nanoparticles, particularly their excitonic and inter-transition properties, are crucial for various applications and are commonly studied using UV–vis absorption spectroscopy. The UV–vis absorption spectrum of CTAB/ZnO NPs is shown in Fig. 4a. This spectrum, covering the range of 350–700 nm, reveals essential information about the optical properties and band structure of the synthesized nanoparticles. The excitonic absorption peak at 400 nm is a significant feature in the UV–vis absorption spectrum of CTAB/ZnO NPs. This peak is attributed to the intrinsic band-gap absorption of ZnO, which corresponds to electron transitions from the valence band to the conduction band (O2p → Zn3d)45. Notably, this absorption peak is red-shifted compared to the absorption peak of bulk ZnO, typically observed at 365 nm. The red shift indicates a decrease in the optical band gap, which is often associated with the presence of shallow levels inside the band gap due to the incorporation of non-native atoms or defects such as oxygen vacancies within the ZnO lattice46.

The red shift observed in the absorption peak of CTAB/ZnO NPs suggests enhanced crystallinity and possibly larger average nanoparticle size compared to bulk ZnO47. The shift to a higher wavelength in the absorption spectrum can be linked to the quantum confinement effect, where the size of the nanoparticles influences their electronic properties. Larger nanoparticles tend to have a narrower band gap due to the reduced quantum confinement effect, leading to the observed red shift. The surfactant cetyltrimethylammonium bromide (CTAB) plays a critical role in the synthesis of ZnO nanoparticles. CTAB helps create a region of high surface energy around the nanoparticles, promoting aggregation and influencing the optical properties48. The surfactant defects introduced by CTAB may contribute to the red shift and affect the crystal size distribution of the nanoparticles.

Tauc’s method was used to derive the optical band gap energy (Eg) from the UV–vis spectrum, as shown in Fig. 4b49,50. The Tauc plot involves plotting (αhν)2 against photon energy (hv), where α is the optical absorbance coefficient, h is Planck’s constant, and ν is the frequency of the incident light. The optical band gap is determined by extrapolating the linear portion of the plot to the x-axis. The calculated Eg value for CTAB/ZnO NPs was found to be 2.82 eV, which is lower than the bulk ZnO value of 3.30 eV47. This reduction in band gap energy is indicative of the presence of crystal quantum defects and the progressive development of the nanoparticles. The narrowing of the optical band gap suggests that CTAB/ZnO NPs could be effective in applications requiring UV–vis light-responsive photocatalysts. The findings align with previous studies that have reported similar red shifts and band gap narrowing in ZnO nanoparticles due to defect states and size effects51–54. For instance, studies have shown that the presence of oxygen vacancies and other defects can introduce additional energy levels within the band gap, facilitating the red shift in absorption spectra.

In conclusion, the optical characterization of CTAB/ZnO NPs using UV–vis absorption spectroscopy revealed crucial insights into their band structure and defect states. The red shift in the absorption peak and the reduction in the optical band gap energy highlight the influence of nanoparticle size, surfactant effects, and defect states on the optical properties. These characteristics make CTAB/ZnO NPs promising candidates for applications in photocatalysis and other fields requiring efficient light absorption and electronic transitions.

Functional group analysis of CTAB/ZnO via Fourier transform infrared spectroscopy (FTIR)

The functionality on the CTAB/ZnO were determined using FTIR spectroscopy. The IR transmittance spectra (4000–500 cm−1) of CTAB, Zn acetate, and CTAB/ZnO NPs are shown in Fig. 5a–c, respectively. The primary absorption band owing to O–H stretching of a hydroxyl group were observed at 3552 and 3406 cm−1 for CTAB (Fig. 5a)55. In the spectrum of zinc acetate solution, bands at 1693 and 1547 cm−1 were suspected due to symmetric and antisymmetric stretching vibrations of the carboxyl groups, respectively. Interestingly, a few new peaks noticed in the FTIR spectra of CTAB loaded ZnO, which was generated due to the interactions between zinc acetate and CTAB during the synthesis of ZnO NPs (Fig. 5c). In FTIR spectra of CTAB/ZnO NPs, the fundamental modes of vibration at 3666, 3614, and 1023 cm−1 were detected due to O–H stretching vibration, intermolecular bonds of water molecules, and hydrogen-bonded hydroxyl groups, respectively. The bands found at 2922 cm−1 correspond to the symmetric-asymmetric stretching vibration of the CH2 group. The vibrations produced by the carboxyl group at 1690 and 1540 cm−1 were due to symmetric and asymmetric modes of vibration, respectively. The existence of absorption peaks at 738 cm−1, and 679 cm−1 revealed the stretching vibrations of ZnO NPs and generally generated due to the creation of tetrahedral coordination of Zn56–59. The existence of the residual hydroxyl peak in CTAB/ZnO NPs is due to the hydroscopic nature of ZnO NPs. The peaks around 750–650 cm−1 can be assigned to the stretching of Zn–O during the formation of the ZnO NPs. A change in particle size and shape is responsible for the shift from the previous band at 645 cm−1 to 679 cm−1. Our findings on the functionality of the synthesized ZnO NPs are in line with previously published report60.Figure 5 FTIR spectra: (a) CTAB, (b) zinc acetate solution, and (c) CTAB-mediated ZnO NPs.

The FTIR analysis reveals significant interactions between CTAB and ZnO during the synthesis process, indicating successful functionalization of ZnO nanoparticles by CTAB. The appearance of new peaks and the shifting of existing peaks in the FTIR spectra confirm the chemical bonding and structural changes induced by CTAB. For instance, the detection of O–H stretching vibrations at multiple wavelengths indicates the presence of hydroxyl groups, which are crucial for the stability and reactivity of ZnO nanoparticles. Additionally, the presence of CH2 stretching vibrations suggests the incorporation of the organic CTAB molecules into the ZnO matrix, which can enhance the dispersibility and prevent agglomeration of nanoparticles. Moreover, the observed peaks related to Zn–O stretching vibrations at 738 cm−1 and 679 cm−1, along with the shift from 645 cm−1, highlight the formation of ZnO nanoparticles with tetrahedral coordination. This shift is indicative of changes in particle size and shape, which are critical factors influencing the optical and electronic properties of ZnO nanoparticles. The residual hydroxyl peaks further suggest the hygroscopic nature of the synthesized nanoparticles, implying that they can readily interact with water molecules, which may be beneficial for certain catalytic and sensing applications.

Overall, the FTIR analysis provides evidence that the synthesis of CTAB/ZnO NPs was effective. It demonstrates notable interactions between CTAB and ZnO, which are supported by the existence of distinct functional groups and their unique vibrations. The identification of additional peaks and changes in the positions of existing ones suggests the creation of ZnO nanoparticles with unique structural characteristics, which are impacted by the capping and stabilising activities of CTAB. The results align with earlier studies and show that CTAB effectively alters the surface chemistry and enhances the stability of ZnO NPs60. The comprehensive spectrum analysis offers valuable information about the functional groups that are present and their significance in the process of synthesising nanoparticles. This study helps us get a deeper knowledge of the chemical characteristics of the material.

Topography analysis of CTAB/ZnO via field emission scanning electron microscopy (FESEM)

A FESEM analysis was carried out to investigate the morphological parameters of synthesised CTAB/ZnO NPs. Additionally, the FESEM was also utilized to understand the effect of CTAB on the topography of ZnO. The FESEM images of CTAB/ZnO NPs are shown in Fig. 6a–d shows. The magnification of a specific location in the FESEM (Fig. 6a) was raised from 25 to 65 KX (Fig. 6b) in order to get an interior perspective of their aggregated shape. The nanocapsule-shaped nanostructure composed of spherical particle aggregates can be seen in the magnified FESEM images. Likewise, as evident from another magnified image in Fig. 6c, diverse shapes, e.g., spherical, hexagonal, and rectangular of ZnO nanostructures were also present. Similarly, clusters of spherical and hexagonal particles were seen in Fig. 6d. Notably, the homogeneity and shape of NPs play a crucial role in defining their applications. The use of CTAB during the synthesis of ZnO NPs significantly affected the morphology of CTAB/ZnO NPs. The presence of CTAB in CTAB/ZnO compelled the aggregation of ZnO into many different nano-structures (e.g., nano-capsules, hexagonal, spherical, and rectangular. It was postulated that due to positive electric charge of ZnO NPs and the cationic head groups of CTAB molecules repulsion between ZnO and CTAB occurred61,62. To overcome these electrostatic repulsive forces, CTAB molecules align in the form of a double layer on the ZnO surface, which caused the aggregation of ZnO particles.Figure 6 FESEM images of CTAB/ZnO NPs at different resolutions: (a) 25 KX, (b–d) 65 KX, and (e) EDX spectrum.

Further, the capping of ZnO NPs with CTAB restricted the lateral development, which changed the topography of ZnO NPs from spherical to rectangular or hexagonal (Fig. 6b–d). More specifically, the cationic part of CTAB interacts electrostatically with zinc species ([Zn(OH)4]2−)63. On the basis of molar ratios of CTAB and zinc species, different topographies of the ZnO (such as hexagonal, rectangular or spherical) can be formed. The elemental analysis of CTAB/ZnO NPs was examined by energy dispersive X-ray spectroscopy (EDAX) (Fig. 6e). In particular, the atomic and weight percentage of oxygen was 48.20% and 18.57%, respectively. On the other hand, the atomic and weight percentage of zinc was 51.80% and 81.43%, respectively. A small deviation in the Zn:O ratio (48.20:51.80) from the standard Zn:O ratio (50:50) may introduce defect states in CTAB/ZnO. These oxygen defects may enhance the light absorption capabilities of the ZnO and lead to high photocatalytic activity.

The investigation of CTAB/ZnO nanoparticles using FESEM demonstrates notable morphological changes caused by CTAB. CTAB’s presence induces the creation of various nanostructures, such as nanocapsules, spheres, hexagons, and rectangles. The differences occur as a consequence of electrostatic interactions between the positively charged ZnO nanoparticles and the cationic head groups of CTAB. This contact leads to the alignment of a double layer, which reduces repulsive forces and encourages the formation of different forms via aggregation. The action of CTAB limits the horizontal expansion of ZnO, causing a change in the surface structure from spherical to more intricate shapes. EDAX analysis provides further evidence of a little deviation in the Zn ratio, suggesting the existence of oxygen defects that increase the absorption of light and boost the photocatalytic activity.

Morphological analysis of CTAB/ZnO via high-resolution transmission electron microscopy (HRTEM)

The HRTEM microscopy technique is a useful tool for obtaining precise information about the structural properties of nanoscale materials such as nanoparticles, nanofibers, and nano-emulsions. In current study HRTEM is used for obtaining particle distribution and a SAED pattern (Fig. 7). The distribution pattern in the micrograph reveals that the particles were of varying sizes and forms (e.g., spherical, capsule, hexagonal, and rectangular) (Fig. 7a). Higher resolution images were captured to better portray the particle morphologies (Fig. 7b, c: 350 KX). The nanostructured findings that were seen in HRTEM agree with those from the FESEM analysis. The histogram for the spread of CTAB/ZnO NP size is shown in Fig. 7d. The particle distributions yielded an average NP size of 31 nm.Figure 7 Morphology of CTAB/ZnO NPs: (a) TEM image (b, c) different morphologies, (d) particle size distribution, (e) HRTEM image, and (f) SAED pattern.

Table 3 describes the various methods used to prepare ZnO NPs along with an assessment of their sizes and shapes. The ZnO NPs prepared with various capping agents (such as tri-n-octylphosphine oxide, triethanolamine, oleic acid, 1-thioglycerol, polyethylene glycol, polyvinyl pyrrolidone, histidine, etc.,) using different methods (such as hydrothermal, precipitation, solvothermal, simple-polyol, co-precipitation, etc.,), showed irregular particle shapes (relative to multi-structured CTAB/ZnO, Table 3). In the above discussion, which focused on the role of capping agents and the way the particles were synthesized, it was found that the photocatalytic activity of the present system (as CTAB/ZnO NPs) may be affected by the shape of the particles. The literature examples chosen for this study show that the type of capping agent and the synthetic method used to make ZnO NPs can have a big effect on how well they work as photocatalysts by changing their structure.Table 3 Summary of the different morphological parameters of ZnO.

Order	Precursor used	Capping agent	Method	Experimental conditions	Dia.	Shape	Refs.	
Solvent	RT*
(oC)	CT* (oC)	
1	(Zn(CO3COO)2∙2H2O)	TOPO	hyd.	DW	400	60	 ~ 1 μm	QS, W-like, H-like	76	
2	(Zn(CO3COO)2∙2H2O)	TEA/OL/TGO	prec.	DMSO	60	0–150	40–45 nm	QS	77	
3	(Zn(CO3COO)2∙2H2O)	PVP	prec.	DW	80	120	 ~ 1 μm	QS	78	
4	(Zn(CO3COO)2∙2H2O)	His	Solv.	EtOH	90	60	 ~ 50 nm	B	79	
5	(Zn(CO3COO)2∙2H2O)	PEG/PVP	sol–gel	EtOH	RT	0	 ~ 20 nm	QS	80	
6	(Zn(CO3COO)2∙2H2O)	PVP	S-P	EG	185	500	249 nm	QS	81	
7	ZnCl2	Gelatin	co-prec.	DDW	RT	100	8–10 nm	QS	44	
8	(Zn(CO3COO)2.2H2O)	PEG/PVP	co-prec.	DW	RT	350	30–50 nm	IR	82	
9	(Zn(CO3COO)2∙2H2O)	PEG	sol–gel	DW	130	80	10–90 nm	QS	83	
10	(Zn(CO3COO)2∙6H2O)	CTAB	prec.-cum-hyd.	DW	60	160	40	MS	Present study	
TOPO, tri-n-octylphosphine oxide; TEA, triethanolamine; OL, oleic acid; TGO, thioglycerol; PEG, polyethylene glycol; PVP, polyvinyl pyrrolidone; His, histidine; CTAB, cetyltrimethyl ammonium bromide; hyd., hydrothermal; prec., precipitation; solv., solvothermal; S-P-, simple-polyol; co-prec., co-precipitation; prec.-cum-hyd., precipitation-cum-hydrothermal; DW, deionized water; DMSO, dimethylsulpoxide; EtOH, ethanol; EG, ethylene glycol; DDW, doubled distilled water; RT*, reaction temperature; RT, room temperature; CT*, calcination temperature; Dia., diameter of particles; QS, Qusi-spherical; W-like, whisker-like; H-like, hexagon-like; B, bead, IR, irregular; MS, multi-structure.

The fringes of CTAB/ZnO NPs were observed via HRTEM at high magnification (500 KX) (Fig. 7e). A well-focused region is denoted by resolved fringes displaying the atomic planes’ d-spacing of 0.23 nm (compared to the usual d-spacing of 0.20–0.25 nm). The existence of a single isolated crystallite suggested that the CTAB/ZnO was mono-crystalline. The SAED pattern of CTAB/ZnO nanostructures was studied using TEM in dark field diffraction mode (Fig. 7f). It shows a defect-free single crystalline pattern with first, second, and third-order facets of nanocrystals. The SAED pattern exhibits a typical diffraction of a ring pattern with some brighter and more defined spots in the rings. This showed the existence of some bigger crystallites, although the rings remained reasonably continuous. It implies that the crystallites were in the nm range and in a random orientation. The electron diffraction spots can be described by a hexagonal crystalline-structured ZnO with a space group P63mc and indices identical to the XRD spectrum of ZnO NPs, as illustrated in Fig. 7f.

The HRTEM examination of CTAB/ZnO nanoparticles demonstrates a variety of morphologies, including spherical, capsule, hexagonal, and rectangular, with an average size of 31 nm, which supports the findings of the FESEM data. The nanoparticles have a monocrystalline nature with a hexagonal crystal structure, as shown by high-resolution pictures and SAED patterns. These images reveal well-defined atomic planes and continuous diffraction rings. Comparative analyses including various capping agents and synthesis techniques emphasise the distinctive capacity of CTAB to regulate the shape and improve the quality of ZnO nanoparticles. Having control over the morphology is essential for maximising the efficiency of photocatalytic activity and other uses.

Chemical analysis of CTAB/ZnO via X-ray photoelectron (XPS) spectroscopy

XPS is one of the most important technique to look at the complicated electronic structure of solids64. The valence status of elements on the surface of CTAB-mediated ZnO NPs was investigated using XPS (Fig. 8). The survey scan shows the presence of Zn, C, and O elements in ZnO NPs (Fig. 8a). Figure 8b–d shows the high-resolution XPS spectrum of Zn 2p, O 1s, and C 1s, respectively. The primary peak at 1020.91 eV corresponds to Zn 2p3/2, whereas the peak at 1044.00 eV corresponds to Zn 2p1/2 Fig. 8b. Zn atoms at the normal lattice location in ZnO are responsible for these emissions. Here, the difference between the binding energies of Zn 2P3/2 and Zn 2P1/2 emissions was found to be 23.09 eV, which is the typical value for ZnO65. As previously stated, the Zn 2P3/2 peak form lacks an asymmetric characteristic, therefore, Zn LMM1 Auger peak analysis is employed to identify the chemical states of the Zn species66. This is due to the fact that Auger peaks usually exhibit larger shape changes than XPS peaks with different chemical states. In our study, an Auger Zn LMM1 emission centred at 472.95 eV is detected and attributed to the interstitial Zn–O bonds. It confirmed an oxygen-rich stoichiometry for the produced ZnO NPs and shows that they lack Zn flaws67.Figure 8 XPS spectra of CTAB mediated ZnO NPs: (a) survey scan, (b) Zn 2p, (c) O 1s, and (d) C 1s.

Figure 8c shows the high-resolution spectrum of O 1s (overall fit and deconvoluted OI, and OII). The strong O peak at 529.71 eV is due to the overall fitting of the metal–oxygen bond of ZnO. The peak at the binding energy 529.51 eV is attributed to the OI of the Zn–O bond. The broad OII peak at a binding energy of 531.21 eV can be ascribed to the defect sites containing low oxygen coordination in ZnO. According to earlier research, the O 1 s state has three binding energy components, including a low binding energy peak at 530.15 eV, a moderate binding energy peak at 530.15 eV, and a high binding energy peak at 532.40 eV68. The low energy peak was caused by O2− ions at oxygenated locations, whereas the middle peak was caused by O2− ions in the oxygen-deficient zone. Chemisorbed oxygen was allocated the high peak. In the other study, three different O peaks were seen at 530.28 eV, 531.30 eV, and 532.36 eV, respectively, which were ascribed to O atoms at regular lattice sites, oxygen-deficient areas, and interstitial O. Figure 8d depict a high-resolution spectrum of C 1s with a peak at 284.51 binding energy, which illustrates the C=O. It can be seen from the XPS analysis that no impurity peaks other than Zn, O, and C species are found.

An XPS examination of ZnO nanoparticles, mediated by CTAB, offers a thorough understanding of surface chemistry. The existence of zinc (Zn), oxygen (O), and carbon (C) components has been verified, and no contaminants have been discovered. The detected Zn 2p and O 1s peaks correspond to the expected values for ZnO, suggesting that the stoichiometry is correct and there is an abundance of oxygen in the bonding. The lack of Zn defects and the existence of well-defined lattice sites and regions with a lower amount of oxygen are verified. The existence of C=O bonds, as shown by the C 1s peak, provides further evidence of the purity of the synthesised nanoparticles.

Investigation of surface area and pore size via BET and BJH for CTAB/ZnO nanoparticles

CTAB-modified zinc oxide nanoparticles exhibit type IV isotherms with a type H3 hysteresis loop, as per the IUPAC classification (Fig. 9a). This specific isotherm shape indicates the presence of mesoporous materials. Mesoporous materials are characterized by pores with diameters ranging from 2 to 50 nm. The observed hysteresis loop, occurring at a relative pressure range of 0.3–1.0, suggests capillary condensation within the mesopores and highlights their slit-like nature. The BET method was employed to calculate the surface area of CTAB/ZnO nanoparticles. Both multi-point and single-point approaches were utilized in the analysis of the isotherm data. The BET surface area of CTAB/ZnO was found to be approximately 102 m2 g−1—a remarkable value that surpasses the reported surface areas for both environmentally friendly and commercially produced ZnO nanoparticles. The superior surface characteristics of CTAB/ZnO make it an attractive material for various applications, especially in photocatalysis. The BJH method provides detailed insights into the mesoporous structure by evaluating the desorption branch of the isotherm (Fig. 9b). For CTAB/ZnO nanoparticles, the pore volume is approximately 0.20 cubic centimetres per gram (c.c. g−1) and the average pore diameter: The average pore diameter is approximately 30 nm. These results confirm the mesoporous nature of CTAB/ZnO nanoparticles and indicate a uniform pore size distribution. Such characteristics are advantageous for applications requiring high surface area and specific pore properties, particularly in photocatalytic processes. The combination of a high BET surface area and the mesoporous structure suggests that CTAB/ZnO nanoparticles possess a highly porous architecture, making them ideal for photocatalytic applications.Figure 9 BET analysis of ZnO nanoparticles: (a) nitrogen adsorption/desorption isotherm with corresponding BET surface area plot (inset), and (b) pore-size/volume distribution employing the BJH method.

Performance evaluation of CTAB/ZnO for the degradation of industrial RB-81 dye

Dye degradation

To get insight into the photocatalytic activity of the produced CTAB/ZnO NPs, experiments were conducted to degrade RB-81 dye. Some reports indicate that the –N=N– chromophore group is mostly responsible for RB-81’s (an azo dye’s) predominant colour69. Due to the presence of two stable, complex aromatic rings linking the group, disassembly of RB-81 is a challenging task. The photostability of the commercial RB-81 dye was initially investigated as a function of time under UV irradiation, even without the use of a photocatalyst (Fig. 10a). The concentration of RB-81 dye did not change after being exposed to UV light for 60 min. These results demonstrate that RB-81 maintains its physical and chemical characteristics when exposed to UV radiation. The photocatalytic activity of the prepared CTAB/ZnO NPs (150 mg L−1) towards RB-81 (120 mg L−1) in the dark and under UV light is shown in Fig. 10b. There was a constant decrease in the absorption peak of RB-81 at 583 nm. In just 105 min under UV light, the absorption peak of RB-81 dye was almost diminished. Moreover, the change in the color of dye solution into translucence (due to degradation of chemical structure of dye) can also be observed to monitor the degradation of dye. The amount of RB-81 dye removed by the different CTAB/ZnO NP concentrations is displayed in Fig. 10c. It has been observed that the amount of photocatalyst present in a reaction may have a significant impact on the total photocatalytic removal efficiency70. Here, the impact of photocatalyst dosage was evaluated at loading levels of 150 and 200 mg L−1. When the photocatalyst dose was raised from 150 to 200 mg L−1, the removal efficiency was increased from 87.20 to 91.75%, which is consistent with an increase in the number of active surface sites. Synthesized CTAB/ZnO was evaluated against a commercial TiO2 P25 photocatalyst for its ability to degrade RB-81 (Fig. 10d). Interestingly, the performance of synthesized CTAB/ZnO was found superior in comparison to the TiO2 P25 especially in terms of photocatalytic activity. The small crystallite size, multi-structure shape, low band-gap energy, and functionalized surface of CTAB/ZnO can be attributed for the above-said better photocatalytic characteristics.Figure 10 Photocatalytic degradation of the RB-81 dye via CTAB/ZnO NPs: (a) dye stability, (b) dye degradation (120 mg L−1), (c) removal efficiency, and (d) comparison of the efficiency.

The photocatalytic mechanism for the degradation of RB-81 dye by CTAB/ZnO is shown in Fig. 11. Upon absorption of light with appropriate wavelength, an electron excited from the valence band to the conduction band of CTAB/ZnO NPs. Then the photogenerated holes and electrons react with the water and oxygen (adsorbed on the CTAB/ZnO surface) to generate hydroxyl (∙OH) and superoxide anion (O2.-) radicals. The resulting ∙OH and O2.- interacts with the RB-81 to degrade and decolourize it.Figure 11 The photocatalytic dye (RB-81) degradation mechanism of the CTAB/ZnO NPs.

In addition, the degradation of Reactive Blue-81 by ZnO is highly dependent on the pH of the solution, as the pH affects both the surface charge of ZnO nanoparticles and the ionization state of the dye molecules. Reactive Blue-81, a synthetic dye with a sulfonate group (-SO3H) in its structure, is anionic in nature, especially at neutral to alkaline pH levels due to the deprotonation of the sulfonate group, resulting in a negatively charged dye molecule.

At lower pH values (acidic conditions), the surface of ZnO nanoparticles tends to be positively charged due to the adsorption of protons (H+ ions). This positive surface charge enhances the electrostatic attraction between the ZnO nanoparticles and the negatively charged Reactive Blue-81 molecules, leading to improved adsorption of the dye onto the catalyst surface. Enhanced adsorption facilitates closer interaction between the dye molecules and the reactive sites on the ZnO surface, promoting more effective photocatalytic degradation. In contrast, at higher pH values (alkaline conditions), the surface of ZnO nanoparticles becomes negatively charged due to the presence of hydroxide ions (OH−). The negative surface charge results in electrostatic repulsion between the ZnO nanoparticles and the negatively charged Reactive Blue-81 molecules, reducing the adsorption efficiency. Consequently, the decreased adsorption leads to less effective photocatalytic degradation of the dye under alkaline conditions. Moreover, the generation of hydroxyl radicals (∙OH), which are crucial oxidizing agents in the photocatalytic degradation process, is influenced by the pH. In alkaline conditions, the production of hydroxyl radicals is generally more favourable, which can enhance the photocatalytic activity. However, the overall degradation efficiency still depends on the balance between the enhanced radical generation and the reduced dye adsorption due to electrostatic repulsion.

Kinetic study and stability

This research utilized a comprehensive approach to understand the photodegradation process of RB-81 dye by the synthesized CTAB/ZnO nanoparticles. We employed a range of kinetic models, including zero-, first-, and second-order, each offering unique insights into the reaction dynamics. The equations used in our study are as follows:12.1 Lt=-x0t+A0

12.2 lnLt=-x1t+lnA0

12.3 1/Lt=x2t+1/A0

In these equations, ‘A0’ represents the absorbance at the start of the reaction, while ‘Lt’ denotes the absorbance at subsequent time intervals. The symbols ‘x0’, ‘x1’, and ‘x2’ are the reaction kinetic rate constants, which provide a measure of the reaction speed.

We conducted an exhaustive study on the degradation of RB-81 dye by CTAB/ZnO nanoparticles. The kinetic fits, as shown in Fig. 12, provide a visual representation of the reaction dynamics under zero-order (a), first-order (b), and second-order (c) conditions. The slope of these graphs corresponds to the reaction rate constant, with a steeper slope indicating a faster dye breakdown. Table 4 presents a summary of the kinetic rates of reactions determined by the various models for different systems. Interestingly, the first-order kinetic model showed the highest agreement with the experimental data, suggesting that this model most accurately describes the reaction dynamics in our system. We also explored the impact of varying the dose of CTAB/ZnO nanoparticles on the kinetic reaction rate for the photo-degradation of RB-81 dye. Our results showed that increasing the nanoparticle dose from 150 to 200 mg L−1 led to an increase in the reaction rate constants. At a dose of 200 mg L−1, the dye degradation was particularly rapid, resulting in the highest rate constant (k1 = 0.00889 min−1) (Table 4).Figure 12 Kinetics model of degradation of RB-81 dye: (a) pseudo-zero-order, (b) pseudo-first-order, and (c) pseudo-second-order.

Table 4 Dye removal apparent reaction rate constants and parameters obtained using various kinetic models.

Order	Sample dose (mg L−1)	% Removal	Zero order	First order	Second order	
k0 (μmol L−1 min−1)	R2	k1 (min−1)	R2	k2 (L μmol min−1)	R2	
1	150	87.20	0.00960	0.85	0.00775	0.98	0.04169	0.94	
2	200	91.75	0.00940	0.85	0.00889	0.98	0.06149	0.84	

Our findings underscore the effectiveness of CTAB/ZnO nanoparticles as a photocatalyst, with a high dye degradation rate of 91.75% achieved in just 105 min. We further tested the stability of CTAB/ZnO nanoparticles by conducting five runs of photodegradation at a dose of 200 mg L−1. Impressively, the removal efficiency of the industrial RB-81 dye remained above 85% even after five cycles (Fig. 13). The slight decrease in photocatalytic efficiency over multiple cycles could be due to the blocking of some active sites on the CTAB/ZnO surface, a finding that could guide future efforts to improve the stability of the photocatalyst.Figure 13 Reusability efficiency of CTAB/ZnO NPs for the RB-81 dye.

Assessment of photocatalytic performance metrics

Dye degradation kinetics and photocatalyst removal efficiency are common metrics used to compare the effectiveness of a photocatalytic systems. Since photocatalytic system performance is highly sensitive to fundamental process factors such as concentration levels of target pollutants or dose of catalysts. A simple calculation of removal efficiency is insufficient for meaningful evaluation. As a result, it is more crucial to concentrate on the impacts of factors that might directly influence the photoactivities of a particular system (e.g., factors such as UV or visible radiation dose, photoreactor geometry, power consumption per unit of pollutant degradation, and dye degradation efficiency). This emphasizes the requirement for additional precise performance measures to make an assessment in order to permit a comparison of the effectiveness of various photocatalytic systems. These performance parameters have thus been generated and are described in Table 5. The photocatalytic activity of the produced ZnO NPs was also evaluated for different dyes and compared with certain similar photocatalytic systems.Table 5 Derived QY, STY, and FOM values for several photocatalytic systems employed for dye degradation.

Order	Photocatalyst	Pollutant used	PMW
(g mol−1)	Wavelength (m)*	PM (g)	RT	LP (W)	PS
(L)	PC
(g L−1)	RE
(%)	APR (moles)	APR (molecules)	Kinetic rxn rate (µmol g−1 h−1)	Number of photons consumed	QY (Φ; molecules photon−1)	SY (molecules photon−1 mg−1)	FOM (molLJ−1 g−1 h−1)	References	
1	ZnO	DB 26	298.29	4.2E-07	0.05	0.50	250	0.1	0.025	83.9	7.03E−06	4.23E+ 18	2.81E+ 02	9.50E+ 23	4.46E−06	8.91E−08	6.25E−11	84	
2	ZnO	MO	327.33	3.7E−07	0.01	0.50	1000	0.05	0.03	99.7	4.57E−06	2.75E+ 18	9.14E+ 02	3.30E+ 24	8.33E−07	8.33E−08	2.54E−11	85	
3	PEG ZnO	MG	364.91	4.2E−07	0.03	1.00	100	0.015	0.016	62.64	4.12E−07	2.48E+ 17	1.37E+ 01	7.60E+ 23	3.26E−07	1.09E−08	5.72E−13	86	
4	CB[8]/ZnO	RBR X 3B	615.30	4.2E−07	0.05	0.66	100	0.05	0.5	95.9	3.90E−05	2.35E+ 19	1.18E+ 03	5.02E+ 23	4.68E−05	9.35E−07	2.48E−10	87	
5	SnO2	MB	319.85	2.5E−07	0.02	2.00	125	0.07	0.01	90.9	1.99E−06	1.20E+ 18	4.97E+ 01	1.13E+ 24	1.06E−06	5.30E−08	3.87E−12	88	
6	TiO2	RY81	1632.18	2.5E−07	1	0.33	100	0.1	0.05	92	2.82E−06	1.70E+ 18	8.54E+ 00	1.49E+ 23	1.14E−05	1.14E−08	7.19E−12	89	
7	TiO2	RV1	926.54	2.5E−07	1	0.33	100	0.1	0.05	85	4.59E−06	2.76E+ 18	1.39E+ 01	1.49E+ 23	1.85E−05	1.85E−08	1.17E−11	89	
8	TiO2–Fe3O4	RTB G133	1098.10	2.5E−07	1	3	100	0.05	0.21	93	8.89E−06	5.36E+ 18	2.96E+ 00	1.36E+ 24	3.94E−06	3.94E−09	1.37E−13	90	
9	TiO2–Fe3O4	RRM8b	879.90	2.5E−07	1	3	100	0.05	0.21	91	1.09E−05	6.54E+ 18	3.62E+ 00	1.36E+ 24	4.82E−06	4.82E−09	1.68E−13	90	
10	TiO2–Fe3O4	BB	466.44	2.5E−07	1	3	100	0.05	0.21	92	2.07E−05	1.25E+ 19	6.90E+ 00	1.36E+ 24	9.19E−06	9.19E−09	3.20E−13	90	
11	S doped TiO2	RB 19	626.50	4.2E−07	0.05	2.00	200	0.1	0.02	90	2.87E−06	1.73E+ 18	2.87E+ 01	3.04E+ 24	5.69E−07	1.14E−08	2.00E−12	91	
12	TiO2	BB 41	482.57	2.5E−07	1	2.00	8	1.2	0.025	92.9	5.78E−05	3.48E+ 19	2.89E+ 01	7.24E+ 22	4.80E−04	4.80E−07	6.02E−10	92	
13	CTAB/ZnO	RB-81	808.49	2.5E−07	0.02	1.75	6	0.1	0.12	91.8	1.36E−05	8.21E+ 18	3.89E+ 02	4.75E+ 22	1.73E−04	8.64E−06	1.03E−09	Present study	
Photocat., photocatalyst; Poll. name, pollutant name; PMW, pollutant molecular weight; PM, photocatalyst mass; RT, reaction time; LP, lamp power; PS, pollutant solution; PC, pollutant concentration; RE, removal efficiency; APR, amount of pollutant removed; QY, quantum yield; SY, space time yield; FOM, figure-of-merit. RY81, reactive yellow 81; RB19, reactive blue 91; RRM8b, reactive Red M8b; RTB G133, reactive Turquoise Blue G 133; RV1, reactive violet 1; MB, methyl blue; RBX 3B, reactive Brilliant Red X-3B; MG, malachite green; MO, methyl orange; DB 26, dispersive blue 26; BB41, basic blue 41.

*λmax = 420 was considered for visible light wherever not reported.

Key considerations for implementing a specific photocatalytic system in the industry are the system's energy consumption and dye degradation rate. Calculating the amount of energy required for a photocatalytic process involves dividing the rate at which pollutant molecules (dye) are degraded by the rate at which incoming photons strike the reaction container87. Here, we looked at the relative photonic efficiency (how many dye molecules were destroyed per unit of photons at a certain wavelength)87. The minimal energy requirement for the RB-81 dye in the current photocatalytic system was 4.75 × 1022 J mol−1 (Table 5).

QY is a useful indicator of a photocatalyst's ability to emit the photons after the absorption of photons in either the UV or visible spectrum87. QY values ranged from 104 to 107 (molecules photon−1) for a wide variety of nanomaterials, including ZnO, PEG/ZnO, CB[8] /ZnO, SnO2, TiO2, TiO2–Fe3O4, and S–TiO2 (Table 5). Multiple factors, including the amount of dye employed, the number of photons utilized for degradation, reactor geometry, analytical methods, and the nature of the light source are crucial in deciding the QY values. CTAB/ZnO had the highest QY value of 1.73 × 10–4 molecules photon−1 among the materials covered in Table 5. Notably, CTAB/ZnO displayed multi-fold higher QY in comparison to the counterparts mentioned in Table 5. The QY values calculated for other common photocatalyst, e.g., TiO2, ZnO/SnO2/TiO2-Fe3O4, and ZnO/S-TiO2are 1.14–1.85 × 10–05, 1.06–4.82 × 10–06, and 5.69–8.33 × 10–07 molecules photon-1, respectively.

Likewise, the kinetic reaction rate (e.g., the number of pollutants degraded by the photocatalyst in a certain period) of the CTAB/ZnO NPs was determined and compared to other photocatalytic systems to characterise their dye degradation kinetics. The as-synthesized CTAB/ZnO NPs had the greatest kinetic reaction rate (3.89 × 102 µmol g−1 h−1), followed by PEG/ZnO (1.37 × 101 µmol g−1 h−1), SnO2 (4.97 × 101 µmol g−1 h−1), TiO2 (8.54 µmol g−1 h−1), TiO2-Fe3O4 (2.96 µmol g−1 h−1), and S-TiO2 (2.87 × 101 µmol g−1 h−1). Prior studies have shown that the photocatalyst's surface morphology greatly affects the reaction rate71.

The other key performance metrics, e.g., STY and FOM was also calculated for CTAB/ZnO and compared with the other recently developed/common photocatalysts (Table 5). As in case of other performance metrics, the as-synthesized CTAB/ZnO NPs outperformed other counterparts in terms of STY with a value of, 8.64 × 10–6 molecules photon−1 mg−1 for the degradation of RB-81 dye. This STY value is much greater than the STY values of other reported ZnO catalysts (9.35 × 10–07 to 1.09 × 10–08 molecules photon−1 mg−1), SnO2, TiO2, TiO2-Fe3O4, and S-TiO2 (4.80 × 10–07 to 1.14 × 10–08 molecules photon−1 mg−1) (Table 5). Consequently, the excellent RB-81 dye degradation capacity of as-synthesized CTAB/ZnO NPs is established. The feasibility of our photocatalytic system’s to be used on an industrial scale was also assessed in terms of FOM (Table 5). The CTAB/ZnO NPs prepared in the present work exhibited the highest FOM value (1.03 × 10–9 mol L J−1 g−1 h−1). The superior photocatalytic structural, optical, and chemical features of CTAB/ZnO NPs can be expected for its high FOM value.

Assessment of antimicrobial activity of CTAB/ZnO NPs

ZnO NPs have special physicochemical characteristics, which have led to extensive research into their possible antibacterial effects. In order to assess the antibacterial effectiveness of NPs, the agar well diffusion method is often used72. In the current study, the antibacterial activity of CTAB/ZnO NPs was evaluated using the agar well diffusion technique. Both were prepared and sterilised by heating the nutritional medium (NM) and agar media (nutritional broth; HiMedia Laboratories) to 120 °C for 20 min. By doing this, it was made sure that the medium was clear of any microbial contamination that would have impacted the experiment's outcomes. (15 mL) of the required medium was placed in clean petri dishes, and the mixture was then given time to settle (Fig. 14). Gram-positive (MRSA) and gram-negative (P. aeruginosa). Gram-negative (P. aeruginosa) and gram-positive (S. aureus) bacteria were injected, and the samples were incubated for 18 h at 40 °C and 140 rpm. After 18 h of growth, the bacterial culture was diluted with fresh NB media at a ratio of 1:100. Reduced pure strains of P. aeruginosa and S. aureus were spread on an NB agar plate. The ZnO solution samples (together with the control specimen) were pipetted into the wells of each plate using micropipettes with capacities of 10, 25, and 40 L. The samples were then incubated for 22 h at 40 °C. Table 6 shows the identification of inhibition zones of various sizes. The spores of gram-negative P. aeruginosa were greenish-blue with a pleasant scent, while the spores of gram-positive S. aureus were yellowish-white with a characteristic sour odour. Both bacteria's development habits have been thoroughly studied under an optical microscope and documented for future study. The experiment’s goal was to see how changing medium affected bacterial development and to evaluate the growth patterns of two distinct species of bacteria. The findings revealed that both microorganisms grew well in the given medium, however P. aeruginosa expanded quicker than S. aureus. These discoveries have important significance for microbiology investigation and may lead to new insights into the emergence of medications and other bacterial illness therapies.Figure 14 Antibacterial activity of CTAB/ZnO NPs.

Table 6 CTAB/ZnO nanoparticles' inhibition zones for P. aeruginosa and S. aureus (gram- positive).

Order	ZnO NPs	10 µL (in cm)	25 µL (in cm)	40 µL (in cm)	
1	S. aureus	1.873	2.234	2.803	
2	P. aeruginosa	2.134	2.525	2.925	

Antimicrobial action mechanism of CTAB-mediated ZnO NPs

Figure 15 depicts a simplified model of the bactericidal effects of CTAB/ZnO NPs against S. aureus and P. aeruginosa. Previous research has shown that the negative charge of microorganism cell walls influences how microbes engage with the NPs or electrons they create. This affects both gram-positive and gram-negative bacteria. The cell wall and membrane protect the microbe from its surroundings, enable equilibrium, and allow nutrition to enter the cell. The presence of CTAB/ZnO in water-based medium leads in the formation of Zn2+ ions. The capacity of nanoparticles to generate reactive oxygen species makes them promising antimicrobial substances. Because of their electrostatic bonds with the cell's outermost section, Zn2+ ions compromise the strength of the bacterial cell wall. When the membrane's stability is weakened, NPs may be allowed to enter the cell and cause oxidative haemorrhaging. Furthermore, the ZnO NPs interact with electrons inside the bacterial cell, amplifying the inhibition of cell development. Because of the breakdown of phosphate and hydrogen bonds, spindles are also destroyed. The interactions between the inorganic metal oxide nanoparticles and the bacterial cell modify the ability to leak of the membrane. This eventually leads to many cell deaths73–75.Figure 15 Schematic of antibacterial action mechanism of CTAB-mediated ZnO NPs.

CTAB/ZnO NPs shown great effectiveness and perseverance, making them ideal for microbial eradication from the environment. As a result, our findings demonstrated the feasibility of producing ZnO NPs with significant antibacterial activity against both gram-positive and gram-negative bacteria.

Conclusion

In the current study, a unique chemical precipitation-cum-hydrothermal process was used to effectively synthesise multi-structured CTAB/ZnO. The synthesised CTAB/ZnO NPs’ exhibited an Eg of 2.82 eV. FESEM and HRTEM images showed that the CTAB inhibits the ZnO NPs’ growth in particular directions and led to the creation of new multi-structures. The developed CTAB/ZnO was found excellent for the photocatalytic degradation of RB-81 under UV irradiation. The developed photocatalyst is tested with several key performance metrics, e.g., QY, STY, and FOM. Notably, the CTAB/ZnO NPs developed in current study outperform previously developed photocatalytic systems (in terms of performance metrics values). Also, the high activity of ZnO nanoparticles makes them beneficial for the eradication of bacteria. The advantageous characteristics of CTAB/ZnO NPs, including small crystallite size, high crystallinity, low Eg, highly functionalized surface, and multi-structured morphologies can be suspected for their superior photocatalytic and antibacterial properties.

Acknowledgements

The author K M Batoo would like to thank Researchers Supporting Project No. (RSP2023R148), King Saud University, Riyadh, Saudi Arabia for the financial support.

Author contributions

S.K., H.K. and M.P. Conception and design of the work. J.G. Draft the article, Data collection and Experiment. G.S., V.K. and K.B. assisted in data analysis. All authors discussed the results and commented on the manuscript at all stages.

Data availability

All data generated or analysed during this study are included in this published article and its supplementary information files.

Competing interests

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
==== Refs
References

1. Ayesha Polyvinylpyrrolidone and chitosan-coated magnetite (Fe3O4) nanoparticles for catalytic and antimicrobial activity with molecular docking analysis J. Environ. Chem. Eng. 2023 11 3 110088 10.1016/j.jece.2023.110088
Ayesha, et al. Polyvinylpyrrolidone and chitosan-coated magnetite (Fe3O4) nanoparticles for catalytic and antimicrobial activity with molecular docking analysis. J. Environ. Chem. Eng. 11(3), 110088 (2023).10.1016/j.jece.2023.110088
2. Ikram M Experimental and computational study of annealed nickel sulfide quantum dots for catalytic and antibacterial activity Nano Mater. Sci. 2023 10.1016/j.nanoms.2023.11.007
Ikram, M. et al. Experimental and computational study of annealed nickel sulfide quantum dots for catalytic and antibacterial activity. Nano Mater. Sci.10.1016/j.nanoms.2023.11.007 (2023).10.1016/j.nanoms.2023.11.007
3. Kaur H Bhatti HS Singh K Europium doping effect on 3D flower-like SnO2 nanostructures: Morphological changes, photocatalytic performance and fluorescence detection of heavy metal ion contamination in drinking water RSC Adv. 2019 9 64 37450 37466 10.1039/C9RA03405F 35542290
Kaur, H., Bhatti, H. S. & Singh, K. Europium doping effect on 3D flower-like SnO2 nanostructures: Morphological changes, photocatalytic performance and fluorescence detection of heavy metal ion contamination in drinking water. RSC Adv. 9(64), 37450–37466. 10.1039/C9RA03405F (2019).35542290 10.1039/C9RA03405F
4. Huang Z Simultaneous and efficient photocatalytic reduction of Cr(VI) and oxidation of trace sulfamethoxazole under LED light by rGO@Cu2O/BiVO4p-n heterojunction composite, (in eng) Chemosphere 2019 221 824 833 10.1016/j.chemosphere.2019.01.087 30684780
Huang, Z. et al. Simultaneous and efficient photocatalytic reduction of Cr(VI) and oxidation of trace sulfamethoxazole under LED light by rGO@Cu2O/BiVO4p-n heterojunction composite, (in eng). Chemosphere 221, 824–833 (2019).30684780 10.1016/j.chemosphere.2019.01.087
5. Zarrin S Heshmatpour F Facile preparation of new nanohybrids for enhancing photocatalytic activity toward removal of organic dyes under visible light irradiation J. Phys. Chem. Solids 2020 140 109271 10.1016/j.jpcs.2019.109271
Zarrin, S. & Heshmatpour, F. Facile preparation of new nanohybrids for enhancing photocatalytic activity toward removal of organic dyes under visible light irradiation. J. Phys. Chem. Solids 140, 109271 (2020).10.1016/j.jpcs.2019.109271
6. Sahoo JK Konar M Rath J Kumar D Sahoo H Magnetic hydroxyapatite nanocomposite: Impact on eriochrome black-T removal and antibacterial activity J. Mol. Liquids 2019 294 111596 10.1016/j.molliq.2019.111596
Sahoo, J. K., Konar, M., Rath, J., Kumar, D. & Sahoo, H. Magnetic hydroxyapatite nanocomposite: Impact on eriochrome black-T removal and antibacterial activity. J. Mol. Liquids 294, 111596 (2019).10.1016/j.molliq.2019.111596
7. Karimi MH Mahdavinia GR Massoumi B Baghban A Saraei M Ionically crosslinked magnetic chitosan/κ-carrageenan bioadsorbents for removal of anionic eriochrome black-T Int. J. Biol. Macromol. 2018 113 361 375 10.1016/j.ijbiomac.2018.02.102 29471096
Karimi, M. H., Mahdavinia, G. R., Massoumi, B., Baghban, A. & Saraei, M. Ionically crosslinked magnetic chitosan/κ-carrageenan bioadsorbents for removal of anionic eriochrome black-T. Int. J. Biol. Macromol. 113, 361–375 (2018).29471096 10.1016/j.ijbiomac.2018.02.102
8. Kaur Y Jasrotia T Kumar R Chaudhary GR Chaudhary S Adsorptive removal of eriochrome black T (EBT) dye by using surface active low cost zinc oxide nanoparticles: A comparative overview, (in eng) Chemosphere 2021 278 130366 10.1016/j.chemosphere.2021.130366 33831687
Kaur, Y., Jasrotia, T., Kumar, R., Chaudhary, G. R. & Chaudhary, S. Adsorptive removal of eriochrome black T (EBT) dye by using surface active low cost zinc oxide nanoparticles: A comparative overview, (in eng). Chemosphere 278, 130366 (2021).33831687 10.1016/j.chemosphere.2021.130366
9. Liu Q Pollution and treatment of dye waste-water IOP Conf. Ser.: Earth Environ. Sci. 2020 514 5 052001
Liu, Q. Pollution and treatment of dye waste-water. IOP Conf. Ser.: Earth Environ. Sci. 514(5), 052001 (2020).
10. Yaseen DA Scholz M Textile dye wastewater characteristics and constituents of synthetic effluents: A critical review Int. J. Environ. Sci. Technol. 2019 16 2 1193 1226 10.1007/s13762-018-2130-z
Yaseen, D. A. & Scholz, M. Textile dye wastewater characteristics and constituents of synthetic effluents: A critical review. Int. J. Environ. Sci. Technol. 16(2), 1193–1226 (2019).10.1007/s13762-018-2130-z
11. Moeen S Comparative study of sonophotocatalytic, photocatalytic, and catalytic activities of magnesium and chitosan-doped tin oxide quantum dots ACS Omega 2022 7 50 46428 46439 10.1021/acsomega.2c05133 36570226
Moeen, S. et al. Comparative study of sonophotocatalytic, photocatalytic, and catalytic activities of magnesium and chitosan-doped tin oxide quantum dots. ACS Omega 7(50), 46428–46439 (2022).36570226 10.1021/acsomega.2c05133
12. Rani S Dye degradation, antimicrobial activity, and molecular docking analysis of samarium-grafted carbon nitride doped-bismuth oxobromide quantum dots Glob. Chall. 2023 7 12 2300118 10.1002/gch2.202300118 38094862
Rani, S. et al. Dye degradation, antimicrobial activity, and molecular docking analysis of samarium-grafted carbon nitride doped-bismuth oxobromide quantum dots. Glob. Chall. 7(12), 2300118 (2023).38094862 10.1002/gch2.202300118
13. Shaheen F Size-controlled synthesis of La and chitosan doped cobalt selenide nanostructures for catalytic and antibacterial activity with molecular docking analysis, (in eng) Int. J. Biol. Macromol. 2024 263 Pt 1 130096 10.1016/j.ijbiomac.2024.130096 38354925
Shaheen, F. et al. Size-controlled synthesis of La and chitosan doped cobalt selenide nanostructures for catalytic and antibacterial activity with molecular docking analysis, (in eng). Int. J. Biol. Macromol. 263(Pt 1), 130096 (2024).38354925 10.1016/j.ijbiomac.2024.130096
14. Rani B Punniyakoti S Sahu NK Polyol asserted hydrothermal synthesis of SnO2 nanoparticles for the fast adsorption and photocatalytic degradation of methylene blue cationic dye New J. Chem. 2018 42 2 943 954 10.1039/C7NJ03341A
Rani, B., Punniyakoti, S. & Sahu, N. K. Polyol asserted hydrothermal synthesis of SnO2 nanoparticles for the fast adsorption and photocatalytic degradation of methylene blue cationic dye. New J. Chem. 42(2), 943–954. 10.1039/C7NJ03341A (2018).10.1039/C7NJ03341A
15. Shahzadi A La-doped CeO2 quantum dots: Novel dye degrader, antibacterial activity, and in silico molecular docking analysis ACS Omega 2023 8 9 8605 8616 10.1021/acsomega.2c07753 36910973
Shahzadi, A. et al. La-doped CeO2 quantum dots: Novel dye degrader, antibacterial activity, and in silico molecular docking analysis. ACS Omega 8(9), 8605–8616 (2023).36910973 10.1021/acsomega.2c07753
16. Bahmani M Dashtian K Mowla D Esmaeilzadeh F Ghaedi M UiO-66(Ti)-Fe3O4-WO3 photocatalyst for efficient ammonia degradation from wastewater into continuous flow-loop thin film slurry flat-plate photoreactor J Hazard. Mater. 2020 393 122360 10.1016/j.jhazmat.2020.122360 32114134
Bahmani, M., Dashtian, K., Mowla, D., Esmaeilzadeh, F. & Ghaedi, M. UiO-66(Ti)-Fe3O4-WO3 photocatalyst for efficient ammonia degradation from wastewater into continuous flow-loop thin film slurry flat-plate photoreactor. J Hazard. Mater. 393, 122360 (2020).32114134 10.1016/j.jhazmat.2020.122360
17. Rao CN Dua P Kuchhal P Lu Y Kale SN Cao P Enhanced sensitivity of magneto-optical sensor using defect induced perovskite metal oxide nanomaterial J. Alloys Compd. 2019 797 896 901 10.1016/j.jallcom.2019.05.118
Rao, C. N. et al. Enhanced sensitivity of magneto-optical sensor using defect induced perovskite metal oxide nanomaterial. J. Alloys Compd. 797, 896–901 (2019).10.1016/j.jallcom.2019.05.118
18. Asha A Narain R Nanomaterials Properties 2020 Elsevier 343 359
Asha, A. & Narain, R. Nanomaterials Properties 343–359 (Elsevier, 2020).
19. Xu L Xian F Zhang Y Wang W Qiu K Xu J Synthesis of ZnO-decorated SnO2 nanopowder with enhanced photocatalytic performance Optik 2019 194 162965 10.1016/j.ijleo.2019.162965
Xu, L. et al. Synthesis of ZnO-decorated SnO2 nanopowder with enhanced photocatalytic performance. Optik 194, 162965 (2019).10.1016/j.ijleo.2019.162965
20. Kazeminezhad I Sadollahkhani A Farbod M Synthesis of ZnO nanoparticles and flower-like nanostructures using nonsono- and sono-electrooxidation methods Mater. Lett. 2013 92 29 32 10.1016/j.matlet.2012.10.064
Kazeminezhad, I., Sadollahkhani, A. & Farbod, M. Synthesis of ZnO nanoparticles and flower-like nanostructures using nonsono- and sono-electrooxidation methods. Mater. Lett. 92, 29–32 (2013).10.1016/j.matlet.2012.10.064
21. Grosso D Balkenende AR Albouy PA Lavergne M Mazerolles L Babonneau F Highly oriented 3D-hexagonal silica thin films produced with cetyltrimethylammonium bromide J. Mater. Chem. 2000 10 9 2085 2089 10.1039/B003178J
Grosso, D. et al. Highly oriented 3D-hexagonal silica thin films produced with cetyltrimethylammonium bromide. J. Mater. Chem. 10(9), 2085–2089. 10.1039/B003178J (2000).10.1039/B003178J
22. Rana SB Influence of CTAB assisted capping on the structural and optical properties of ZnO nanoparticles J. Mater. Sci.: Mater. Electron. 2017 28 18 13787 13796
Rana, S. B. Influence of CTAB assisted capping on the structural and optical properties of ZnO nanoparticles. J. Mater. Sci.: Mater. Electron. 28(18), 13787–13796 (2017).
23. Mishra SK Srivastava RK Prakash SG Yadav RS Panday AC Photoluminescence and photoconductive characteristics of hydrothermally synthesized ZnO nanoparticles Opto-Electron. Rev. 2010 18 4 467 473 10.2478/s11772-010-0037-4
Mishra, S. K., Srivastava, R. K., Prakash, S. G., Yadav, R. S. & Panday, A. C. Photoluminescence and photoconductive characteristics of hydrothermally synthesized ZnO nanoparticles. Opto-Electron. Rev. 18(4), 467–473 (2010).10.2478/s11772-010-0037-4
24. Rahman MYA Umar AA Taslim R Salleh MM Effect of surfactant on the physical properties of ZnO nanorods and the performance of ZnO photoelectrochemical cell J. Exp. Nanosci. 2015 10 8 599 609 10.1080/17458080.2013.858374
Rahman, M. Y. A., Umar, A. A., Taslim, R. & Salleh, M. M. Effect of surfactant on the physical properties of ZnO nanorods and the performance of ZnO photoelectrochemical cell. J. Exp. Nanosci. 10(8), 599–609 (2015).10.1080/17458080.2013.858374
25. Rajput RB Kale RB Hydro/solvothermally synthesized visible light driven modified SnO2 heterostructure as a photocatalyst for water remediation: A review Environ. Adv. 2021 5 100081 10.1016/j.envadv.2021.100081
Rajput, R. B. & Kale, R. B. Hydro/solvothermally synthesized visible light driven modified SnO2 heterostructure as a photocatalyst for water remediation: A review. Environ. Adv. 5, 100081 (2021).10.1016/j.envadv.2021.100081
26. Liu W Treatment of CrVI-containing Mg(OH)2 nanowaste Angew. Chem. Int. Ed. 2008 47 30 5619 5622 10.1002/anie.200800172
Liu, W. et al. Treatment of CrVI-containing Mg(OH)2 nanowaste. Angew. Chem. Int. Ed. 47(30), 5619–5622 (2008).10.1002/anie.200800172
27. Xue Y Liu X Zhang N Shao Y Xu CC Enhanced photocatalytic performance of iron oxides@HTCC fabricated from zinc extraction tailings for methylene blue degradation: Investigation of the photocatalytic mechanism Int. J. Miner. Metall. Mater. 2023 30 12 2364 2374 10.1007/s12613-023-2723-5
Xue, Y., Liu, X., Zhang, N., Shao, Y. & Xu, C. C. Enhanced photocatalytic performance of iron oxides@HTCC fabricated from zinc extraction tailings for methylene blue degradation: Investigation of the photocatalytic mechanism. Int. J. Miner. Metall. Mater. 30(12), 2364–2374 (2023).10.1007/s12613-023-2723-5
28. Yu F Π-Skeleton tailoring of olefin-linked covalent organic frameworks achieving low exciton binding energy for photo-enhanced uranium extraction from seawater Adv. Funct. Mater. 2024 34 1 2307230 10.1002/adfm.202307230
Yu, F. et al. Π-Skeleton tailoring of olefin-linked covalent organic frameworks achieving low exciton binding energy for photo-enhanced uranium extraction from seawater. Adv. Funct. Mater. 34(1), 2307230 (2024).10.1002/adfm.202307230
29. Zhang Q Accelerating photocatalytic hydrogen production by anchoring Pt single atoms on few-layer g-C3N4 nanosheets with Pt–N coordination J. Mater. Chem. C 2024 12 10 3437 3449 10.1039/D3TC04673G
Zhang, Q. et al. Accelerating photocatalytic hydrogen production by anchoring Pt single atoms on few-layer g-C3N4 nanosheets with Pt–N coordination. J. Mater. Chem. C 12(10), 3437–3449. 10.1039/D3TC04673G (2024).10.1039/D3TC04673G
30. Ameh T Zarzosa K Dickinson J Braswell WE Sayes CM Nanoparticle surface stabilizing agents influence antibacterial action, (in eng) Front. Microbiol. 2023 14 1119550 10.3389/fmicb.2023.1119550 36846763
Ameh, T., Zarzosa, K., Dickinson, J., Braswell, W. E. & Sayes, C. M. Nanoparticle surface stabilizing agents influence antibacterial action, (in eng). Front. Microbiol. 14, 1119550 (2023).36846763 10.3389/fmicb.2023.1119550
31. Kaur N An efficient and viable photodegradation of a textile Reactive yellow-86 dye under direct sunlight by multi-structured Fe2O3 encapsulated with phytochemicals of R. Indica J. Mater. Sci.: Mater. Electron. 2020 31 1 15
Kaur, N. et al. An efficient and viable photodegradation of a textile Reactive yellow-86 dye under direct sunlight by multi-structured Fe2O3 encapsulated with phytochemicals of R. Indica. J. Mater. Sci.: Mater. Electron. 31, 1–15 (2020).
32. Vikrant K Kim K-H Deep A Photocatalytic mineralization of hydrogen sulfide as a dual-phase technique for hydrogen production and environmental remediation Appl. Catal. B: Env. 2019 259 118025 10.1016/j.apcatb.2019.118025
Vikrant, K., Kim, K.-H. & Deep, A. Photocatalytic mineralization of hydrogen sulfide as a dual-phase technique for hydrogen production and environmental remediation. Appl. Catal. B: Env. 259, 118025 (2019).10.1016/j.apcatb.2019.118025
33. Raza N Solar-light-active silver phosphate/titanium dioxide/silica heterostructures for photocatalytic removal of organic dye J. Clean. Prod. 2020 254 120031 10.1016/j.jclepro.2020.120031
Raza, N. et al. Solar-light-active silver phosphate/titanium dioxide/silica heterostructures for photocatalytic removal of organic dye. J. Clean. Prod. 254, 120031 (2020).10.1016/j.jclepro.2020.120031
34. Ramesh M Anbuvannan M Viruthagiri G Green synthesis of ZnO nanoparticles using Solanum nigrum leaf extract and their antibacterial activity, (in eng) Spectrochim. Acta A Mol. Biomol. Spectrosc. 2015 136 864 870 10.1016/j.saa.2014.09.105 25459609
Ramesh, M., Anbuvannan, M. & Viruthagiri, G. Green synthesis of ZnO nanoparticles using Solanum nigrum leaf extract and their antibacterial activity, (in eng). Spectrochim. Acta A Mol. Biomol. Spectrosc. 136, 864–870 (2015).25459609 10.1016/j.saa.2014.09.105
35. Hsiao C-C Yu S-Y Improved response of ZnO films for pyroelectric devices Sensors 2012 12 12 17007 17022 10.3390/s121217007 23235444
Hsiao, C.-C. & Yu, S.-Y. Improved response of ZnO films for pyroelectric devices. Sensors 12(12), 17007–17022. 10.3390/s121217007 (2012).23235444 10.3390/s121217007
36. Lahure P Plasma X-ray diffraction study of ZnO nanoparticles Int. J. Sci. Res. Phys. Appl. Sci. 2015 3 1 32 33
Lahure, P. et al. Plasma X-ray diffraction study of ZnO nanoparticles. Int. J. Sci. Res. Phys. Appl. Sci. 3(1), 32–33 (2015).
37. Sharma R Bisen DP Shukla U Sharma BG X-ray diffraction: A powerful method of characterizing nanomaterials Recent Res. Sci. Technol. 2012 4 8
Sharma, R., Bisen, D. P., Shukla, U. & Sharma, B. G. X-ray diffraction: A powerful method of characterizing nanomaterials. Recent Res. Sci. Technol. 4, 8 (2012).
38. Bindu P Thomas S Estimation of lattice strain in ZnO nanoparticles: X-ray peak profile analysis J. Theor. Appl. Phys. 2014 8 4 123 134 10.1007/s40094-014-0141-9
Bindu, P. & Thomas, S. Estimation of lattice strain in ZnO nanoparticles: X-ray peak profile analysis. J. Theor. Appl. Phys. 8(4), 123–134 (2014).10.1007/s40094-014-0141-9
39. Srinivas M Preparation, characterization and photocatalytic activity of nickel-substituted CoFe2O4: Exploration of changes in the micro structural parameters and distribution of cations in the lattice Mater. Res. Express 2019 6 11 11509 10.1088/2053-1591/ab51af
Srinivas, M. Preparation, characterization and photocatalytic activity of nickel-substituted CoFe2O4: Exploration of changes in the micro structural parameters and distribution of cations in the lattice. Mater. Res. Express 6(11), 11509 (2019).10.1088/2053-1591/ab51af
40. Musa I Qamhieh N Mahmoud ST Synthesis and length dependent photoluminescence property of zinc oxide nanorods Results Phys. 2017 7 3552 3556 10.1016/j.rinp.2017.09.035
Musa, I., Qamhieh, N. & Mahmoud, S. T. Synthesis and length dependent photoluminescence property of zinc oxide nanorods. Results Phys. 7, 3552–3556 (2017).10.1016/j.rinp.2017.09.035
41. Zeng H Cai W Li Y Hu J Liu P Composition/structural evolution and optical properties of ZnO/Zn nanoparticles by laser ablation in liquid media J. Phys. Chem. B 2005 109 39 18260 18266 10.1021/jp052258n 16853349
Zeng, H., Cai, W., Li, Y., Hu, J. & Liu, P. Composition/structural evolution and optical properties of ZnO/Zn nanoparticles by laser ablation in liquid media. J. Phys. Chem. B 109(39), 18260–18266 (2005).16853349 10.1021/jp052258n
42. Rabiei M Palevicius A Monshi A Nasiri S Vilkauskas A Janusas G Comparing methods for calculating nano crystal size of natural hydroxyapatite using X-Ray diffraction Nanomaterials 2020 10 9 10.3390/nano10091627
Rabiei, M. et al. Comparing methods for calculating nano crystal size of natural hydroxyapatite using X-Ray diffraction. Nanomaterials 10, 9 (2020).10.3390/nano10091627
43. Monshi A Foroughi MR Monshi M Modified Scherrer equation to estimate more accurately nano-crystallite size using XRD World J. Nano Sci. Eng. 2012 2 154 160 10.4236/wjnse.2012.23020
Monshi, A., Foroughi, M. R. & Monshi, M. Modified Scherrer equation to estimate more accurately nano-crystallite size using XRD. World J. Nano Sci. Eng. 2, 154–160 (2012).10.4236/wjnse.2012.23020
44. Khorsand-Zak A Darroudi AMWHM Yousefi R Synthesis and characterization of ZnO nanoparticles prepared in gelatin media Mater. Lett. 2011 65 70 73 10.1016/j.matlet.2010.09.029
Khorsand-Zak, A., Darroudi, A. M. W. H. M. & Yousefi, R. Synthesis and characterization of ZnO nanoparticles prepared in gelatin media. Mater. Lett. 65, 70–73 (2011).10.1016/j.matlet.2010.09.029
45. Zak AK Abrishami ME Majid WHA Yousefi R Hosseini SM Effects of annealing temperature on some structural and optical properties of ZnO nanoparticles prepared by a modified sol–gel combustion method Ceram. Int. 2011 37 1 393 398 10.1016/j.ceramint.2010.08.017
Zak, A. K., Abrishami, M. E., Majid, W. H. A., Yousefi, R. & Hosseini, S. M. Effects of annealing temperature on some structural and optical properties of ZnO nanoparticles prepared by a modified sol–gel combustion method. Ceram. Int. 37(1), 393–398 (2011).10.1016/j.ceramint.2010.08.017
46. Mukherjee A Mitra P Characterization of Sn Doped ZnS thin films synthesized by CBD Mater. Res. (Sao Carlos, Online) 2017 20 2 430 435 10.1590/1980-5373-mr-2016-0628
Mukherjee, A. & Mitra, P. Characterization of Sn Doped ZnS thin films synthesized by CBD. Mater. Res. (Sao Carlos, Online) 20(2), 430–435 (2017).10.1590/1980-5373-mr-2016-0628
47. Solati E Dorranian D Effect of temperature on the characteristics of ZnO nanoparticles produced by laser ablation in water Bull. Mater. Sci. 2016 39 7 1677 1684 10.1007/s12034-016-1315-7
Solati, E. & Dorranian, D. Effect of temperature on the characteristics of ZnO nanoparticles produced by laser ablation in water. Bull. Mater. Sci. 39(7), 1677–1684 (2016).10.1007/s12034-016-1315-7
48. Azizi S Belhaj M Zargouni S Dridi C Correlation between composition, morphology and optical properties of PVK:n-ZnO:CTAB thin films Appl. Phys. A 2017 123 7 475 10.1007/s00339-017-1095-y
Azizi, S., Belhaj, M., Zargouni, S. & Dridi, C. Correlation between composition, morphology and optical properties of PVK:n-ZnO:CTAB thin films. Appl. Phys. A 123(7), 475 (2017).10.1007/s00339-017-1095-y
49. Barman K Chowdhury D Baruah PK Bio-synthesized silver nanoparticles using Zingiber officinale rhizome extract as efficient catalyst for the degradation of environmental pollutants Inorg. Nano-Metal Chem. 2020 50 2 57 65 10.1080/24701556.2019.1661468
Barman, K., Chowdhury, D. & Baruah, P. K. Bio-synthesized silver nanoparticles using Zingiber officinale rhizome extract as efficient catalyst for the degradation of environmental pollutants. Inorg. Nano-Metal Chem. 50(2), 57–65 (2020).10.1080/24701556.2019.1661468
50. Yang Y The design and growth of peanut-like CuS/BiVO4 composites for photoelectrochemical sensing RSC Adv. 2020 10 25 14670 14678 10.1039/D0RA01307B 35497162
Yang, Y. et al. The design and growth of peanut-like CuS/BiVO4 composites for photoelectrochemical sensing. RSC Adv. 10(25), 14670–14678. 10.1039/D0RA01307B (2020).35497162 10.1039/D0RA01307B
51. Wooten AJ Werder DJ Williams DJ Casson JL Hollingsworth JA Solution-liquid-solid growth of ternary Cu-In-Se semiconductor nanowires from multiple- and single-source precursors, (in eng) J. Am. Chem. Soc. 2009 131 44 16177 16188 10.1021/ja905730n 19839616
Wooten, A. J., Werder, D. J., Williams, D. J., Casson, J. L. & Hollingsworth, J. A. Solution-liquid-solid growth of ternary Cu-In-Se semiconductor nanowires from multiple- and single-source precursors, (in eng). J. Am. Chem. Soc. 131(44), 16177–16188 (2009).19839616 10.1021/ja905730n
52. Reddy AJ Combustion synthesis, characterization and Raman studies of ZnO nanopowders, (in eng) Spectrochim. Acta A Mol. Biomol. Spectrosc. 2011 81 1 53 58 10.1016/j.saa.2011.05.043 21764361
Reddy, A. J. et al. Combustion synthesis, characterization and Raman studies of ZnO nanopowders, (in eng). Spectrochim. Acta A Mol. Biomol. Spectrosc. 81(1), 53–58 (2011).21764361 10.1016/j.saa.2011.05.043
53. Baskoutas S Bester G Conventional optics from unconventional electronics in ZnO quantum dots J. Phys. Chem. C 2010 114 20 9301 9307 10.1021/jp101921g
Baskoutas, S. & Bester, G. Conventional optics from unconventional electronics in ZnO quantum dots. J. Phys. Chem. C 114(20), 9301–9307 (2010).10.1021/jp101921g
54. Pudukudy M Yaakob Z Facile synthesis of quasi spherical ZnO nanoparticles with excellent photocatalytic activity J. Cluster Sci. 2015 26 4 1187 1201 10.1007/s10876-014-0806-1
Pudukudy, M. & Yaakob, Z. Facile synthesis of quasi spherical ZnO nanoparticles with excellent photocatalytic activity. J. Cluster Sci. 26(4), 1187–1201 (2015).10.1007/s10876-014-0806-1
55. Mukherjee S Das-Nath S Bhadra P Effect of two different types of capping agents on the synthesis and characterisation of zinc oxide Interceram. Int. Ceram. Rev. 2017 66 5 166 170 10.1007/BF03401211
Mukherjee, S., Das-Nath, S. & Bhadra, P. Effect of two different types of capping agents on the synthesis and characterisation of zinc oxide. Interceram. Int. Ceram. Rev. 66(5), 166–170 (2017).10.1007/BF03401211
56. Liufu S-C Xiao H-N Li Y-P Thermal analysis and degradation mechanism of polyacrylate/ZnO nanocomposites Polym. Degrad. Stab. 2005 87 1 103 110 10.1016/j.polymdegradstab.2004.07.011
Liufu, S.-C., Xiao, H.-N. & Li, Y.-P. Thermal analysis and degradation mechanism of polyacrylate/ZnO nanocomposites. Polym. Degrad. Stab. 87(1), 103–110 (2005).10.1016/j.polymdegradstab.2004.07.011
57. Kwon YJ Kim K Lim C Shim K Characterization of ZnO nanopowders synthesized by the polymerized complex method via an organochemical route J. Ceram. Process. Res. 2002 3 146 149
Kwon, Y. J., Kim, K., Lim, C. & Shim, K. Characterization of ZnO nanopowders synthesized by the polymerized complex method via an organochemical route. J. Ceram. Process. Res. 3, 146–149 (2002).
58. Rana S Singh R Investigation of structural, optical, magnetic properties and antibacterial activity of Ni-doped zinc oxide nanoparticles J. Mater. Sci.: Mater. Electron. 2016 27 9346 9355
Rana, S. & Singh, R. Investigation of structural, optical, magnetic properties and antibacterial activity of Ni-doped zinc oxide nanoparticles. J. Mater. Sci.: Mater. Electron. 27, 9346–9355 (2016).
59. Silva RF Zaniquelli MED Morphology of nanometric size particulate aluminium-doped zinc oxide films Colloids Surfaces A: Physicochem. Eng. Aspects 2002 198–200 551 558 10.1016/S0927-7757(01)00959-1
Silva, R. F. & Zaniquelli, M. E. D. Morphology of nanometric size particulate aluminium-doped zinc oxide films. Colloids Surfaces A: Physicochem. Eng. Aspects 198–200, 551–558 (2002).10.1016/S0927-7757(01)00959-1
60. Suwanboon SJSA Structural and optical properties of nanocrystalline ZnO powder from sol-gel method Science 2008 34 1 31 34
Suwanboon, S. J. S. A. Structural and optical properties of nanocrystalline ZnO powder from sol-gel method. Science 34(1), 31–34 (2008).
61. Usui H The effect of surfactants on the morphology and optical properties of precipitated wurtzite ZnO Mater. Lett. 2009 63 17 1489 1492 10.1016/j.matlet.2009.03.054
Usui, H. The effect of surfactants on the morphology and optical properties of precipitated wurtzite ZnO. Mater. Lett. 63(17), 1489–1492 (2009).10.1016/j.matlet.2009.03.054
62. Campanelli AR Scaramuzza L Hexadecyltrimethylammonium bromide Acta Crystallogr. Sect. C 1986 42 10 1380 1383 10.1107/S0108270186092193
Campanelli, A. R. & Scaramuzza, L. Hexadecyltrimethylammonium bromide. Acta Crystallogr. Sect. C 42(10), 1380–1383 (1986).10.1107/S0108270186092193
63. Basnet P Chatterjee S Structure-directing property and growth mechanism induced by capping agents in nanostructured ZnO during hydrothermal synthesis—a systematic review Nano-Struct. Nano-Objects 2020 22 100426 10.1016/j.nanoso.2020.100426
Basnet, P. & Chatterjee, S. Structure-directing property and growth mechanism induced by capping agents in nanostructured ZnO during hydrothermal synthesis—a systematic review. Nano-Struct. Nano-Objects 22, 100426 (2020).10.1016/j.nanoso.2020.100426
64. Islam MN Ghosh TB Chopra KL Acharya HN XPS and X-ray diffraction studies of aluminum-doped zinc oxide transparent conducting films Thin Solid Films 1996 280 1 20 25 10.1016/0040-6090(95)08239-5
Islam, M. N., Ghosh, T. B., Chopra, K. L. & Acharya, H. N. XPS and X-ray diffraction studies of aluminum-doped zinc oxide transparent conducting films. Thin Solid Films 280(1), 20–25 (1996).10.1016/0040-6090(95)08239-5
65. Pandey S Effect of growth temperature on structural, electrical and optical properties of dual ion beam sputtered ZnO thin films J. Mater. Sci. Mater. Electron. 2013 24 2541 10.1007/s10854-013-1130-5
Pandey, S. et al. Effect of growth temperature on structural, electrical and optical properties of dual ion beam sputtered ZnO thin films. J. Mater. Sci. Mater. Electron. 24, 2541 (2013).10.1007/s10854-013-1130-5
66. Ilyas U Oxygen rich p-type ZnO thin films using wet chemical route with enhanced carrier concentration by temperature-dependent tuning of acceptor defects J. Appl. Phys. 2011 110 9 093522 10.1063/1.3660284
Ilyas, U. et al. Oxygen rich p-type ZnO thin films using wet chemical route with enhanced carrier concentration by temperature-dependent tuning of acceptor defects. J. Appl. Phys. 110(9), 093522 (2011).10.1063/1.3660284
67. Sahai A Goswami N Probing the dominance of interstitial oxygen defects in ZnO nanoparticles through structural and optical characterizations Ceram. Int. 2014 40 9 14569 14578 10.1016/j.ceramint.2014.06.041
Sahai, A. & Goswami, N. Probing the dominance of interstitial oxygen defects in ZnO nanoparticles through structural and optical characterizations. Ceram. Int. 40(9), 14569–14578 (2014).10.1016/j.ceramint.2014.06.041
68. Hai-Bo F Investigation of oxygen vacancy and interstitial oxygen defects in ZnO films by photoluminescence and x-ray photoelectron spectroscopy Chin. Phys. Lett. 2007 24 7 2108 2111 10.1088/0256-307X/24/7/089
Hai-Bo, F. et al. Investigation of oxygen vacancy and interstitial oxygen defects in ZnO films by photoluminescence and x-ray photoelectron spectroscopy. Chin. Phys. Lett. 24(7), 2108–2111 (2007).10.1088/0256-307X/24/7/089
69. Wagner M Eicheler C Helmreich B Hilbig H Heinz D Removal of Congo red from aqueous solutions at hardened cement paste surfaces, (in English) Front. Mater. 2020 7 145 10.3389/fmats.2020.567130
Wagner, M., Eicheler, C., Helmreich, B., Hilbig, H. & Heinz, D. Removal of Congo red from aqueous solutions at hardened cement paste surfaces, (in English). Front. Mater. 7, 145 (2020).10.3389/fmats.2020.567130
70. Singh A Structurally and morphologically engineered single-pot biogenic synthesis of NiO nanoparticles with enhanced photocatalytic and antimicrobial activities J. Clean. Prod. 2022 343 131026 10.1016/j.jclepro.2022.131026
Singh, A. et al. Structurally and morphologically engineered single-pot biogenic synthesis of NiO nanoparticles with enhanced photocatalytic and antimicrobial activities. J. Clean. Prod. 343, 131026 (2022).10.1016/j.jclepro.2022.131026
71. Kumar S Kaur G Rawat M Tsang YF Lin K-Y Kim K-H Potential of Piper betle@Co3O4 nanoparticles as high-performance photocatalysts for the removal of industrial dyes J. Clean. Prod. 2022 361 132242 10.1016/j.jclepro.2022.132242
Kumar, S. et al. Potential of Piper betle@Co3O4 nanoparticles as high-performance photocatalysts for the removal of industrial dyes. J. Clean. Prod. 361, 132242 (2022).10.1016/j.jclepro.2022.132242
72. Balouiri M Sadiki M Ibnsouda SK Methods for in vitro evaluating antimicrobial activity: A review J. Pharmaceut. Anal. 2016 6 2 71 79
Balouiri, M., Sadiki, M. & Ibnsouda, S. K. Methods for in vitro evaluating antimicrobial activity: A review. J. Pharmaceut. Anal. 6(2), 71–79 (2016).
73. Liu K Triarylboron-doped acenethiophenes as organic sonosensitizers for highly efficient sonodynamic therapy with low phototoxicity Adv. Mater. 2022 34 49 2206594 10.1002/adma.202206594
Liu, K. et al. Triarylboron-doped acenethiophenes as organic sonosensitizers for highly efficient sonodynamic therapy with low phototoxicity. Adv. Mater. 34(49), 2206594 (2022).10.1002/adma.202206594
74. Wang Z Fernández-Blanco C Chen J Veiga MC Kennes C Effect of electron acceptors on product selectivity and carbon flux in carbon chain elongation with Megasphaera hexanoica Sci. Total Env. 2024 912 169509 10.1016/j.scitotenv.2023.169509 38141983
Wang, Z., Fernández-Blanco, C., Chen, J., Veiga, M. C. & Kennes, C. Effect of electron acceptors on product selectivity and carbon flux in carbon chain elongation with Megasphaera hexanoica. Sci. Total Env. 912, 169509 (2024).38141983 10.1016/j.scitotenv.2023.169509
75. Zhao Y Dong Y Chen X Wang Z Cui Z Ni S-Q Using sulfide as nitrite oxidizing bacteria inhibitor for the successful coupling of partial nitrification-anammox and sulfur autotrophic denitrification in one reactor Chem. Eng. J. 2023 475 146286 10.1016/j.cej.2023.146286
Zhao, Y. et al. Using sulfide as nitrite oxidizing bacteria inhibitor for the successful coupling of partial nitrification-anammox and sulfur autotrophic denitrification in one reactor. Chem. Eng. J. 475, 146286 (2023).10.1016/j.cej.2023.146286
76. Shahroosvand H Ghorbani-asl M Hydrothermal synthesis of TOPO-capped ZnO nanoparticle Synth. React. Inorg. Metal-Org. Nano-Metal Chem. 2013 43 1 29 39 10.1080/15533174.2012.682689
Shahroosvand, H. & Ghorbani-asl, M. Hydrothermal synthesis of TOPO-capped ZnO nanoparticle. Synth. React. Inorg. Metal-Org. Nano-Metal Chem. 43(1), 29–39 (2013).10.1080/15533174.2012.682689
77. Singh AK Viswanath V Janu VC Synthesis, effect of capping agents, structural, optical and photoluminescence properties of ZnO nanoparticles J. Luminesc. 2009 129 8 874 878 10.1016/j.jlumin.2009.03.027
Singh, A. K., Viswanath, V. & Janu, V. C. Synthesis, effect of capping agents, structural, optical and photoluminescence properties of ZnO nanoparticles. J. Luminesc. 129(8), 874–878 (2009).10.1016/j.jlumin.2009.03.027
78. Gurushankar K Jeyavijayan S Gohulkumar M Viswanathan K Synthesis, optical and morphological studies of ZnO nanoparticles capped with PVP as a surfactant Int. J. Chem. Sci. 2018 16 1 240
Gurushankar, K., Jeyavijayan, S., Gohulkumar, M. & Viswanathan, K. Synthesis, optical and morphological studies of ZnO nanoparticles capped with PVP as a surfactant. Int. J. Chem. Sci. 16(1), 240 (2018).
79. Tanna JA Chaudhary RG Juneja HD Gandhare NV Rai AR Histidine-Capped ZnO nanoparticles: An efficient synthesis, spectral characterization and effective antibacterial activity BioNanoScience 2015 5 3 123 134 10.1007/s12668-015-0170-0
Tanna, J. A., Chaudhary, R. G., Juneja, H. D., Gandhare, N. V. & Rai, A. R. Histidine-Capped ZnO nanoparticles: An efficient synthesis, spectral characterization and effective antibacterial activity. BioNanoScience 5(3), 123–134 (2015).10.1007/s12668-015-0170-0
80. Tachikawa S Noguchi A Tsuge T Hara M Odawara O Wada H Optical properties of ZnO nanoparticles capped with polymers Materials 2023 4 6 1132 1143 10.3390/ma4061132
Tachikawa, S. et al. Optical properties of ZnO nanoparticles capped with polymers. Materials 4(6), 1132–1143. 10.3390/ma4061132 (2023).10.3390/ma4061132
81. Flores-Carrasco G Morpho-structural and chemical composition properties of PVP-Capped ZnO nanoparticles synthesized via a simple-polyol method Solid State Phen. 2019 286 15 22 10.4028/www.scientific.net/SSP.286.15
Flores-Carrasco, G. et al. Morpho-structural and chemical composition properties of PVP-Capped ZnO nanoparticles synthesized via a simple-polyol method. Solid State Phen. 286, 15–22 (2019).10.4028/www.scientific.net/SSP.286.15
82. Javed R Usman M Tabassum S Zia M Effect of capping agents: Structural, optical and biological properties of ZnO nanoparticles Appl. Surface Sci. 2016 386 319 326 10.1016/j.apsusc.2016.06.042
Javed, R., Usman, M., Tabassum, S. & Zia, M. Effect of capping agents: Structural, optical and biological properties of ZnO nanoparticles. Appl. Surface Sci. 386, 319–326 (2016).10.1016/j.apsusc.2016.06.042
83. Meshram JV Koli VB Kumbhar SG Borde LC Phadatare MR Pawar SH Structural, spectroscopic and anti-microbial inspection of PEG capped ZnO nanoparticles for biomedical applications Mater. Res. Express 2018 5 4 045016 10.1088/2053-1591/aab917
Meshram, J. V. et al. Structural, spectroscopic and anti-microbial inspection of PEG capped ZnO nanoparticles for biomedical applications. Mater. Res. Express 5(4), 045016 (2018).10.1088/2053-1591/aab917
84. Hussain ZA Fakhri FH Alesary HF Ahmed LM ZnO based material as photocatalyst for treating the textile anthraquinone derivative dye (dispersive blue 26 dye): Removal and photocatalytic treatment J. Phys.: Conf. Ser. 2020 1664 1 012064
Hussain, Z. A., Fakhri, F. H., Alesary, H. F. & Ahmed, L. M. ZnO based material as photocatalyst for treating the textile anthraquinone derivative dye (dispersive blue 26 dye): Removal and photocatalytic treatment. J. Phys.: Conf. Ser. 1664(1), 012064 (2020).
85. Chen X Wu Z Liu D Gao Z Preparation of ZnO photocatalyst for the efficient and rapid photocatalytic degradation of azo dyes Nanoscale Res. Lett. 2017 12 1 143 10.1186/s11671-017-1904-4 28235375
Chen, X., Wu, Z., Liu, D. & Gao, Z. Preparation of ZnO photocatalyst for the efficient and rapid photocatalytic degradation of azo dyes. Nanoscale Res. Lett. 12(1), 143 (2017).28235375 10.1186/s11671-017-1904-4
86. Jose A Pinheiro SDKRD Narayana S Electrochemical synthesis, photodegradation and antibacterial properties of PEG capped zinc oxide nanoparticles J. Photochem. Photobiol. B: Biol. 2018 187 56 10.1016/j.jphotobiol.2018.07.022
Jose, A., Pinheiro, S. D. K. R. D. & Narayana, S. Electrochemical synthesis, photodegradation and antibacterial properties of PEG capped zinc oxide nanoparticles. J. Photochem. Photobiol. B: Biol. 187, 56 (2018).10.1016/j.jphotobiol.2018.07.022
87. Li L The synthesis of CB[8]/ZnO composites materials with enhanced photocatalytic activities, (in eng) Heliyon 2019 5 5 e01714 10.1016/j.heliyon.2019.e01714 31193292
Li, L. et al. The synthesis of CB[8]/ZnO composites materials with enhanced photocatalytic activities, (in eng). Heliyon 5(5), e01714 (2019).31193292 10.1016/j.heliyon.2019.e01714
88. Tammina DSK Mandal B Nalinee-kanth K Photocatalytic degradation of methylene blue dye by nonconventional synthesized SnO 2 nanoparticles Environ. Nanotechnol. Monitor. Manage. 2018 10 123
Tammina, D. S. K., Mandal, B. & Nalinee-kanth, K. Photocatalytic degradation of methylene blue dye by nonconventional synthesized SnO 2 nanoparticles. Environ. Nanotechnol. Monitor. Manage. 10, 123 (2018).
89. Giwa A Nkeonye P Bello K Kolawole E Campos A Solar photocatalytic degradation of reactive Yellow 81 and reactive violet 1 in aqueous solution containing semiconductor oxides Int. J. Appl. Sci. Technol. 2012 2 56
Giwa, A., Nkeonye, P., Bello, K., Kolawole, E. & Campos, A. Solar photocatalytic degradation of reactive Yellow 81 and reactive violet 1 in aqueous solution containing semiconductor oxides. Int. J. Appl. Sci. Technol. 2, 56 (2012).
90. Vianney YM Rosalyn I Angela S Solar based photocatalytic decolorization of four commercial reactive dyes utilizing bound TiO2-Fe3O4 nanocomposite J. Indones. J. Chem. 2018 18 621 10.22146/ijc.27549
Vianney, Y. M., Rosalyn, I. & Angela, S. Solar based photocatalytic decolorization of four commercial reactive dyes utilizing bound TiO2-Fe3O4 nanocomposite. J. Indones. J. Chem. 18, 621 (2018).10.22146/ijc.27549
91. Khan MAN Siddique M Wahid F Khan R Removal of reactive blue 19 dye by sono, photo and sonophotocatalytic oxidation using visible light Ultrason. Sonochem. 2015 26 370 377 10.1016/j.ultsonch.2015.04.012 25899438
Khan, M. A. N., Siddique, M., Wahid, F. & Khan, R. Removal of reactive blue 19 dye by sono, photo and sonophotocatalytic oxidation using visible light. Ultrason. Sonochem. 26, 370–377 (2015).25899438 10.1016/j.ultsonch.2015.04.012
92. Mohammadi-aghdam S Olya ME Degradation of C. I. basic blue 41 using modified TiO2 nanocomposite in a rectangular semibatch photoreactor J Progress Color Color. Coat. 2014 8 1 47 57
Mohammadi-aghdam, S. & Olya, M. E. Degradation of C. I. basic blue 41 using modified TiO2 nanocomposite in a rectangular semibatch photoreactor. J Progress Color Color. Coat. 8(1), 47–57 (2014).
