Vertically aligned zinc oxide nanosheet for high-performance photocatalysis of water pollutants (original) (raw)
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Design and Synthesis of Efficient ZnO Nanomaterials for Photocatalysis
Current Microwave Chemistry, 2014
Metal oxide-based semiconductor photocatalysis has attracted much attention in recent years. In the cutting edge of efficient photocatalysis, various synthetic and modification strategies of oxides on the nanometer scale have evolved for surface tuning properties. Thus, it is interesting to study recent progresses in the development of surface tuned metal oxide-based nanomaterials as efficient photocatalysts. In this work, special importance, especially facile and feasible approaches is given to develop surface tuned, high thermal stability and hierarchically structured novel ZnO/Zn nanocrystallites. We also investigated the impact of both aggregation phenomenon and photoinduced charge separation in metal oxide nanoparticles. The photocatalytic ability of nano ZnO/Zn on the photodegradation of methylene blue under UV irradiation was investigated in aqueous solution. The result obtained in this work is a key to the rational design of mesoporous nanoparticle networks and helps to engineer composite nanomaterials for photocatalysis.
Journal of Materials Science, 2014
A simple soft chemical method has been suggested for large-scale production of zinc oxide (ZnO) nanosheets at room temperature using two synthesis mediums: aqueous (H 2 O) and non-aqueous (C 2 H 5 OH). In H 2 O medium, nanosheets interwoven group wise in flowerlike structures revealing the strong inter-hydrogen bonding among initially nucleated ZnO nanocrystals, whereas weak hydrogen bonding in C 2 H 5 OH medium leads to the formation of un-aggregated interwoven' nanosheets. The growth of ZnO flower-like and interwoven nanosheets proceeded via anisotropic oriented attachment of ZnO nanocrystals. Obtained nanosheets were faceted, possessing large surface area, width hundreds of nanometers, and thickness in tens of nanometer, as characterized by scanning electron microscopy and transmission electron microscopy. These nanosheets show high sunlight photocatalytic activity toward the degradation of an organic pollutant 'methylene blue dye.' The enhancement in photodegradation efficiencies, interwoven sheets 99.94 %, and flower-like nanosheets 79.76 % for 120 min of irradiation is attributed to the surface oxygen vacancies narrowing the band gap as confirmed by photoluminescence spectra, faceted geometry, and large surface area of ZnO nanosheets.
Facile synthesis of ZnO nanosheets as ultraviolet photocatalyst
Journal of Sol-Gel Science and Technology, 2018
ZnO powders were prepared by solution combustion synthesis method by means of sodium dodecyl sulfate (SDS) as fuel and SDS-citric acid mixed fuel at various fuel contents. Phase evolution studied by X-ray powder diffractometry showed single phase ZnO powders were directly formed by using mixed fuels, while the layered Zn 4 SO 4 (OH) 6 .nH 2 O impurity phase together with ZnO was formed by SDS fuel alone. The as-combusted ZnO powders using SDS fuel are composed of hexagonal nanosheets with the thickness of 70 nm, as observed by electron microscopy. However, the spongy powders with spherical particles achieved by mixture of fuels exhibited higher specific surface area on account of larger amounts of released gaseous products during combustion. The ZnO catalyst prepared by mixed fuel at ϕ = 0.75 showed the highest photodegradation (~96%) of methylene blue (MB), while about only 6% of MB was photodegraded by ZnO nanosheets under ultraviolet light irradiation.
Design and photocatalytic activity of nanosized zinc oxides
Applied Surface Science, 2016
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights There is correlation between synthesis, structure and properties of nanoscaled ZnO's. The photocatalytic activity of ZnO under Vis radiation depends on its band gap level. The ZnO granulometry dominated its efficiency in AOP under UV radiation. Tribophysical treatment has a dual impact on the ZnO photocatalytic activity.
Environmental technology, 2016
ZnO nanoparticles of rod-like architecture have excellent potential to be used in wastewater treatment as a photocatalyst. They were synthesized by utilizing sonochemical/hydration- dehydration techniques using glutamine as a biotemplate. The effects of calcination temperatures, that is, 300°C, 500°C, and 700°C, on the crystallinity, optical properties, and photocatalytic activity of synthesized zinc oxide nanoparticles were investigated. X-ray diffraction (XRD) results indicated that all calcinated samples have a crystalline hexagonal wurtzite structure. Morphology and elemental compositions were investigated using field emission-scanning electron microscopy with energy-dispersive X-ray spectroscopy. The XRD and Fourier transform infrared (FTIR) spectra revealed that the samples were amorphous at 100°C; however, it changed into a crystalline structure amid the calcination process. Optical properties were determined using a UV-visible reflection spectrophotometer and showed abatemen...
Journal of Analytical Methods in Chemistry, 2021
In this study, the physical properties of ZnO were facile controlled by the synthesis method with the addition of capping and precipitation agents. As-prepared ZnO samples had different morphologies such as carnation flower-like ZnO (CF-ZnO), rose-flower-like ZnO (RF-ZnO), rod-like ZnO (R-ZnO), and nanoparticle ZnO (N-ZnO) and were characterized by SEM, XRD, N2 adsorption/desorption isotherms, FT-IR, and DR/UV-vis. All samples had a crystallite structure of hexagonal wurtzite type. The CF-ZnO and RF-ZnO samples had the hierarchical structure like a carnation flower and a beautiful rose, respectively. R-ZnO was composed of many hexagonal rods and few spherical particles, while N-ZnO microstructures were made up of nanoparticles with approximately 20–30 nm, exhibiting the largest surface area, pore volume, and pore width among as-prepared samples, and their crystal size and bandgap energy were 17.8 nm and 3.207 eV, respectively. The catalytic performances of ZnO samples were evaluated...
Environmental Degradation: Causes and Remediation Strategies, 2020
Recently, hierarchical 3D nanostructures have attracted attention due to their multiple advantages, such as large surface area, porous structures, as well as enhanced light harvesting ability. Zinc oxide is a promising photocatalyst alternative to TiO2 used for environmental remediation of wastewater pollutants due to its high photosensitivity, non-toxic nature, low cost, and environmental friendliness. ZnO can be crystallized in three forms under different conditions i.e., wurtzite, zinc-blende, and rock-salt structures. ZnO exhibits a higher quantum efficiency and has a similar bandgap as TiO2 as it has a larger number of inherent active defect sites on the surface, which makes it capable of absorbing a larger fraction of the solar spectrum. Various approaches have been used to efficiently utilize the solar radiation and to enhance the efficiency of zinc oxide photocatalyst. These techniques enhance the photocatalytic performance ZnO under visible light by shifting the bandgap energy, suppressing the recombination rate of electron-hole pairs, increasing charge separation efficiency. In future there is a need of developing green, scalable, low-cost and highly efficient hierarchically ZnO nanostructures and nanocomposites photocatayst for remediation of wastewater pollution. In this chapter the emphasis has been on the advantages, fabrication methods, and photocatalytic applications of hierarchical ZnO nanostructures for the degradation of organic contaminants present in wastewater.
Ceramics International, 2018
A facile low temperature wet chemical synthesis of ZnO nanosheets with tunable thickness is reported. Well defined ZnO nanosheets were obtained by simply varying the zinc precursor (zinc acetate, zinc sulphate and zinc nitrate). The effects of counter ions on the morphological, optical, structural and photocatalytic behavior of the synthesized ZnO nanosheets were investigated. Atomic force microscopy studies revealed appreciable changes in the morphology and significant decrease in the thickness (from 23 nm to 9.5 nm) of ZnO nanosheets as the counter ions were changed from acetate to sulphate ions. Photoluminescence spectroscopy and 2 optical absorption studies showed that the counter ions appreciably affect the optical properties of the prepared nanosheets. The intensity of UV emissions from ZnO nanosheets followed the order of counter ions: acetate < sulphate < nitrate. Photocatalytic removal of methylene blue by the prepared ZnO nanosheets was also studied. The photocatalytic activity of ZnO nanosheets followed the order of counter ions: acetate > sulphate > nitrate. The origins of the observed subtle changes in the thickness and the variations in the optical, morphological and photocatalytic behavior of ZnO nanosheets with variation in the counter ions are tentatively proposed.
Tailoring the photocatalytic activity of nanoparticulate zinc oxide by transition metal oxide doping
Materials Chemistry and Physics, 2009
The successful use of nanoparticulate ZnO in applications such as UV-screening agents or photocatalyst for the destruction of chemical waste requires the development of techniques for controlling its photocatalytic activity. In this study, we have investigated transition metal doping as a means of achieving this goal. Powders of ZnO, Mn x Zn 1−x O, and Co x Zn 1−x O were synthesised by a three-stage process consisting of highenergy mechanical milling, heat treatment, and washing. The photocatalytic activity of these powders was evaluated using the spin-trapping technique with electron paramagnetic resonance spectroscopy. It was found that the photocatalytic activity of Co x Zn 1−x O progressively decreased with the doping level. In contrast, the activity of Mn x Zn 1−x O initially increased with doping up to a level of 2 mol% and thereafter declined. These results demonstrate that doping with transition metal oxides can be used to tailor the photocatalytic properties of nanoparticulate ZnO.
Applied Catalysis B: …, 2010
The aim of this study was to evaluate the effectiveness of using a range of innovative nanostructured high surface area zinc oxide (ZnO) thin films as photocatalysts, and thereafter to systematically relate initial and reacted surface morphology and irradiated surface area to photocatalytic activity under both limited and rich oxygen conditions. The thin films were produced using an innovative combination of magnetron sputtered surfaces and hydrothermal solution deposition that allows the morphology, porosity and thickness to be controlled by varying the composition and processing conditions. Methylene Blue (MB) was chosen as the model compound and the reaction was performed with ultra violet light (UV) at 254 nm. The thin film morphology and surface area before and after reaction was determined by scanning electron microscopy (SEM). The photocatalytic activity (measured as the rate and extent of MB degradation) was determined for seven different ZnO nanostructured thin films: three different ZnO hydrothermal solution depositions on bare glass slides (S1-CG, S2-CG and S3-CG films), the same three ZnO hydrothermal solution depositions but on glass slides coated with a magnetron sputtered ZnO film (S1-MS, S2-MS and S3-MS films), and glass slides coated with just a magnetron sputtered ZnO film (MS films).