Nano ZnO Material Research Articles

Preparation and optical properties of ZnO/ZnS heterostructured nanomaterials

Firstly, Nano-ZnO materials are obtained by hydrothermal method, and Zinc acetate (Zn(CH3COO)2·2H2O) is selected as the Zn source, and potassium hydroxide (KOH) is used as the analytical reagent. Secondly, ZnO/ZnS composites are prepared by hydrothermal method using monomer nano-ZnO as a template, thioacetamide (CH3CSNH2) as a sulfur source, hexadecyl trimethyl Ammonium bromide (CTAB) as a surface modifier, and adjusting the molar mass ratio of Zn/S. The structure, morphology, and optical properties of the composite are characterized respectively by XRD, SEM, and PL, and the growth mechanism and fluorescence characteristics of the composite are explored. The results indicate that the crystal structure of the ZnO/ZnS complex is initially a hexagonal wurtzite structure. With the gradual increase of S element concentration, only the crystal plane diffraction peak of sphalerite structure ZnS is shown in the XRD spectrum. Besides, the morphology of the composite also grows from microsphere like to flocculent layered nano-crystals. There are strong characteristic absorption and green light absorption capabilities at 523 nm, and there is a relatively weak ultraviolet emission peak appeared at 380 nm in the PL spectrum. The optical properties and visible light absorption capabilities of the nano-ZnO/ZnS composite are superior to those of the monomer ZnO. Finally, the growth mechanism and luminescence mechanism of ZnO/ZnS are explored at the micro-level.

Effect of Microwave Irradiation on Physical Adsorption Accuracy and Photocatalytic Activity of Nano-ZnO Materials

Trace toxic organic compounds, such as dyes and polymer additives, can cause serious environmental pollution and threaten human health. Therefore, photocatalytic degradation of organic dye pollutants as an abiotic means has attracted much attention. In the process of preparing ZnO by precipitation method, a series of nano-ZnO materials were obtained by microwave radiation with different power. The crystal structure, morphology and surface physicochemical properties of the synthesized materials were characterized. The results show that the surface area has different degrees of increase compared with the ZnO prepared by the ordinary precipitation method. After different power microwave irradiation, the photocatalytic activity of ZnO has been improved to different extents, and is significantly higher than the commercially available P25 and ZnO without microwave irradiation.

Study on hydrothermal synthesis and photoelectric properties of nano-ZnO

The Nano-ZnO material was synthesized by using the hydrothermal method. The structure, morphology and optical properties of Nano-ZnO material was studied by changing the concentration ratio of Zn(CH3COO)2•2H2O and NaOH. The experimental results showed that, as the concentration ratio of Zn2+ and OH− decreased gradually, the crystallinity of Nano-ZnO sample would increase gradually. The morphology of the sample firstly changed from sheet to rod-like, and finally changed from rod-like to sheet. It indicated that the concentration ratio of Zn2+ and OH− was the main factor determining the morphology of Nano-ZnO. The optical property test results showed that, there appeared a distinct ultraviolet emission peak of Nano-ZnO near 380 nm; there appeared an extremely strong visible light emission band in the wavelength range of 450–650 nm; the luminescence intensity of Nano-ZnO would significantly increase with a decrease in the concentration ratio of Zn2+ and OH−; both the ultraviolet emission peak and the visible light emission band were blue-shifted.

Multifractal analysis of ZnO nanoparticles.

ZnO nanoparticles (NPs) have variety of applications in different fields due to its size, structure, as well as physical and chemical properties. One of its prominent characteristics is its antibacterial behavior. Nonlinear Dynamical Theory (NLD) has a vast scope in the field of material science, especially when subtle correlations are searched for to extract hidden information. Since nano-ZnO materials may be used in inhibiting pathogens, its nonlinear features can be quantified and calibrated with the help of NLD tools. Multi-fractal Analysis (MFA) is an important diagnostic tool of NLD for not only analyzing nonlinear signal or images, but also predicting any spurious events likely to occur in the system under study. Thus, the analysis of the surface texture of the ZnO nano particles formed, using the TEM images and relate it with the variations of the XRD signal using NLD tools, is our first attempt reported here. Further, tools of MFA are used, for the first time, to see if there exists any correlation between the texture of the nano particles formed and the Zone of Inhibition (ZoI) we obtain as an output after allowing certain pathogens inhibit in the presence of the same nano particles. Analysis of TEM images guide us to predict the texture and structure of crystallites of ZnO:Cu samples which are responsible for overall behavior of inhibiting pathogens. In this paper, MFA of ZoI images, TEM images, and signal of four different Cu-doped ZnO nanoparticles are carried out and their outcomes are calibrated for estimating the size and pattern of unknown NPs synthesized under similar physical and chemical condition. Moreover, that MFA can be used reliably to predict spurious or abnormal surface structure or bacterial inhibition is also established.

The Effect of Different Coupling Agents on Nano-ZnO Materials Obtained via the Sol–Gel Process

Hybrid nanomaterials based on zinc oxide were synthesized via the sol–gel method, using different silane coupling agents: (3-glycidyloxypropyl)trimethoxysilane (GPTMS), phenyltriethoxysilane (PhTES), octyltriethoxysilane (OTES), and octadecyltriethoxysilane (ODTES). Morphological properties and the silane precursor type effect on the particle size were investigated using dynamic light scattering (DLS), environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The bonding characteristics of modified ZnO materials were investigated using Fourier transform infrared spectroscopy (FTIR). The final solutions were deposited on metallic substrate (aluminum) in order to realize coatings with various wettability and roughness. The morphological studies, obtained by ESEM and TEM analysis, showed that the sizes of the ZnO nanoparticles are changed as function of silane precursor used in synthesis. The thermal stability of modified ZnO materials showed that the degradation of the alkyl groups takes place in the 300–500 °C range. Water wettability study revealed a contact angle of 142 ± 5° for the surface covered with ZnO material modified with ODTES and showed that the water contact angle increases as the alkyl chain from the silica precursor increases. These modified ZnO materials, therefore, can be easily incorporated in coatings for various applications such as anti-corrosion and anti-icing.

Preparation of Flower-Like ZnO Nanoparticles by High-Gravity Assisted Ammonia Decomposition Method and Their Photoluminescence Properties

Zinc oxide (ZnO) nanoparticles with tunable particle size and photoluminescence (PL) properties were successfully prepared by a facile ammonia decomposition method in a rotating packed bed (RPB) reactor. The zinc-ammonia complex, generated from chemical process of zinc mineral, reacted with steam to precipitate the precursor of ZnO. It was found that both the particle size of ZnO and the precipitation rates of Zn strongly depended on the steam flow rate, high-gravity level, calcination temperature. The flower-like ZnO with primary particle size of ~45 nm had improved PL performance, which further confirmed the intensification of RPB reactor. Moreover, the results showed that the precipitation rate of Zn could reach up to 98% under the optimized conditions. It was believed that RPB reactors with well mass transfer and mixing performances, short preparation time and low energy consumption would be a promising device for the continuous preparation of nano-ZnO materials.

Investigation and Characterization of ZnO Nanostructures Synthesized by Electrochemical Deposition

ZnO with cube-like nanostructures have been fabricated on tin-doped indium oxide (ITO) coated glass substrates via electrochemical deposition method. The electrolytes used containing equimolar of zinc chloride (ZnCl2) and potassium chloride (KCl) ranging from 0.05M to 0.2M. The samples produced subsequently were examined by field emission scanning electron microscope (FESEM), x-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectroscopy and current transient profile. The average size of the cube-like nano ZnO materials, as observed from FESEM images is decreased from 207nm to 102nm with increasing of electrolytes concentration. The XRD measurement indicated that the as-deposited nanostructures are converted from amorphous to hexagonal wurtzite ZnO phase after heat treatment at 600°C for 3hours. Photoresponse measurement revealed that the grown sample is sensitive to the 372nm ultraviolet (UV) light.

Fabrication of ZnO Nanoparticles for Photocatalytic Reduction of CO2

ZnO nanoparticles were fabricated by anodization method. Different fabrication conditions, including pH buffers (sodium hydroxide, citric acid, oxalic acid, hydrogen peroxide), electrolyte concentration, temperature and voltage were investigated. The field emission scanning electron microscopes (FESEMs) revealed that zinc oxide nanoparticles with discal morphology were formed. The optimum conditions for fabrication of nano ZnO material with discal shape nanoparticles are 1wt% NH 4 F electrolyte in water ethano(1:1) solution at 25°C and 40v with 0.2M citric acid as pH buffer. This ZnO material shows rather high photocatalytic reduction activity of CO 2 and the yield of CH 4 reaches 2.48 umol/g catalyst.

Developing Environmentally Friendly Wood Composite Panels by Nanotechnology

Nanoscience and nanotechnology provide numerous opportunities for enhancing the properties of wood composites. Formaldehyde emissions from wood composites are of great importance because of their negative impact on human health. Developing low formaldehyde-emitting particleboard and plywood panels as environmentally friendly composites by nanotechnology was the object of this study. The urea formaldehyde and melamine urea formaldehyde resins that were used to produce particleboard and plywood panels, respectively, were reinforced with various nanomaterials at different loading levels. Formaldehyde emission tests were carried out according to standard TS 4894 EN 120. The results acquired in this work indicated that nanomaterial reinforcement significantly affected the formaldehyde emission properties of the particleboard and plywood panels. Formaldehyde emissions of the composite panels decreased after reinforcement with nanoSiO2, nanoAl2O3, and nanoZnO materials at proper loading levels. Therefore, using nanotechnology, it is possible to produce environmentally friendly wood composite panels with low formaldehyde emissions.

A Novel Temperature Sensor Based on Gold Interdigital Electrodes and Nano ZnO Particles

Nano ZnO is an important kind of semiconductor materials, and it has been widely used in various single detection fields. In this paper, we prepared nano ZnO powder through direct precipitation method. We fabricated temperature sensor utilizing the interdigitated Au electrodes drop-deposited by nano ZnO powder. The response of the sensor to temperature was studied by CHI660 electrical chemical workstation. The results proved that the temperature sensor based on nano ZnO material presented sensitivity and repeatibility

Effect of synthesis method variables on particle size in the preparation of homogeneous doped nano ZnO material

Homogeneous doped ZnO nanoparticles were synthesised by the Pechini method. A statistical experimental design was used to study the effects of the synthesis method variables on the particle size. The variables were the molar ratios of the reagents and the calcination temperature. The results indicated that the calcination temperature was the only factor that had a significant effect on the particle size. The particle size of ZnO varied between 16 and 76 nm with calcination temperatures of 400–800 °C. The homogeneity was studied by the ICP-MS technique, and the powders were found to be highly homogeneous.

X-ray diffraction characterization of the microstructure of close-packed hexagonal nanomaterials

A general least-squares technique for X-ray diffraction line broadening analysis has been developed. The technique can be used to determine single, double, and triple line broadening effects caused by small particle sizes, microstrain, stacking faults, or all three presented in a closed-packed hexagonal nanomaterial. The technique was applied to characterize the microstructure of β-Ni(OH)2, a negative electrode material in nickel-metal hydride (NiMH) batteries. Double line broadening effects caused by both small crystallite sizes and stacking faults in β-Ni(OH)2 were detected and analyzed. Triple line broadening effects caused simultaneously by small crystallite sizes, microstrain, and stacking faults were detected in β-Ni(OH)2 after activation and charge-discharge cycle tests. The triple line broadening effects were found to be selective and most pronounced for diffraction lines with h−k=3n±1. The broadening effects were larger when l=even, but smaller when l=odd. The shape and the average size of the crystallites, microstrain, and stacking fault probability in β-Ni(OH)2 changed dramatically after activation and charge-discharge cycles. The method was also applied to characterize and investigate the microstructure of nano ZnO materials. Results indicate that no selective broadening appears in the XRD patterns of the nano ZnO materials. The average crystallite sizes were different slightly, and the stacking fault probabilities differed significantly with different dopants.

Photocatalytic degradation and mineralization of a malodorous compound (dimethyldisulfide) using a continuous flow reactor

Dimethyldisulfide (DMDS) degradation and mineralization were carried out in a continuous flow reactor using TiO 2-P25 or ZnO as photocatalysts. The efficiency of the disappearance and of the mineralization of the DMDS showed to be very sensitive to the molar flow of the sulphur compounds. In our study, we have evaluated the limit average mineralization rate of DMDS per Watt emitted (for TiO 2-P25). Catalyst deactivation has been observed after several hours of complete DMDS mineralization, which was expressed by the decrease of CO 2 concentration and the appearance of residual DMDS on the outlet side of the reactor. This phenomenon is due to the inhibition of active sites on the catalyst by the formation of sulfates as final sulphur-compounds (determined by ionic chromatography). The FT-IR analysis, performed on catalyst in presence of high DMDS flow, indicated the presence of partial oxidation products such as sulfoxides, sulfones, sulfonates, sulfates and carbonyl groups. All of these disappearing after static irradiation, except for sulfate according to ionic chromatography analysis. The effect of humidity is shown; the data indicated that a detrimental effect occurs depending on the DMDS/H 2O concentration ratio. Comparison of the disappearance and of the mineralization of DMDS in presence of TiO 2-P25, commercial ZnO or home made nano-ZnO catalysts is presented and discussed. Nano-ZnO material, prepared at low temperature, showed an efficiency close to that of TiO 2-P25 while no activity was detected in the presence of commercial ZnO.

Microstructural analysis of varistors prepared from nanosize ZnO

ZnO nanoparticles were prepared by a solid state pyrolysis reaction of zinc acetate dihydrate and oxalic acid dihydrate at 500°C. The course of reaction at various temperatures was followed by XRD. Subsequently varistors were fabricated from this nano-ZnO material by solid state mixing with various oxide additives and sintering to 1050°C. The microstructure of the sintered material was studied using XRD, field emission SEM (FESEM), and EDX, and ZnO grains, bismuth rich regions and spinel phases were identified. Discs made from oxide doped nanoZnO show considerably higher breakdown voltage (656 ± 30 V mm-1) compared to those prepared from micrometre sized ZnO (410 ± 30 V mm-1) and commercial varistors (454 ± 30 V mm-1). However, varistors made from the nano-ZnO show very low densification and high leakage current, making them unsuitable for device fabrication.