Microwave-assisted biosynthesis and characterization of ZnO film for photocatalytic application in methylene blue degradation

This study aims to investigate the physical characteristics and photocatalyst activity of biosynthesized ZnO with pineapple (Ananas comosus) peel extract under microwave irradiation. The ZnO powder was prepared in two different concentrations of zinc nitrate hexahydrate (ZNH) at 200mM (Z-200) and 500 mM (Z-500). The optical, structural, and morphological properties of ZnO were analyzed using UV-Vis spectroscopy, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), respectively. The UV-Vis absorption spectrum showed a wide absorbance peak of ZnO at the wavelength of 300-360 nm with a bandgap energy of 3.22 and 3.25 eV. The XRD result confirmed the wurtzite structure of ZnO with high crystallinity. SEM morphology showed spherical particles with an average particle size of 190-220 nm. For photocatalytic application, ZnO film was fabricated via the doctor blade method from microwave-assisted biosynthesized ZnO powder. ZnO films were then applied under UV-irradiation to examine the photocatalytic degradation of methylene blue. It was found that the catalytic behavior of ZnO film was affected by the starting ZNH concentration with maximum effectiveness of 46% degradation after 2 h.

The Role of the Activator Additives Introduction Method in the Cold Sintering Process of ZnO Ceramics: CSP/SPS Approach

The great prospects for introducing the cold sintering process (CSP) into industry determine the importance of finding approaches to reduce the processing time and mechanical pressure required to obtain dense ceramics using CSP. The introducing zinc acetate into the initial ZnO powder of methods, such as impregnation, thermovapor autoclave treatment (TVT), and direct injection of an aqueous solution into a die followed by cold sintering process using a spark plasma sintering unit, was studied. The effect of the introduction methods on the density and grain size of sintered ceramics was analyzed using SEM, dynamic light scattering, IR spectroscopy, and XRD. The impregnation method provides sintered samples with high relative density (over 0.90) and significant grain growth when sintered at 250 °C with a high heating rate of 100 °C/min, under a uniaxial pressure of 80 MPa in a vacuum, and a short isothermic dwell time (5 min). The TVT and aqueous solution direct injection methods showed lower relative densities (0.87 and 0.76, respectively) of CSP ZnO samples. Finally, the development of ideas about the processes occurring in an aqueous medium with CSP and TVT, which are subject to mechanical pressure, is presented.

Combining X-ray excited optical luminescence and X-ray absorption spectroscopy for correlative imaging on the nanoscale

X-ray absorption and optical luminescence can both provide valuable but very different information on the chemical and physical properties of materials. Although it is known that the spectral characteristics of many materials are highly heterogeneous on the micro- and/or nanoscale, no methodology has so far been shown to be capable of spatially resolving both full X-ray absorption and X-ray excited optical luminescence (XEOL) spectra on the nanoscale in a correlative manner. For this purpose, the scanning transmission X-ray microscope at the HERMES beamline of the SOLEIL synchrotron was equipped with an optical detection system capable of recording high-resolution XEOL spectra using a 40 nm soft X-ray probe. The functionality of the system was demonstrated by analyzing ZnO powder dispersions — showing simultaneously the X-ray linear dichroism and XEOL behavior of individual submicrometric ZnO crystallites.

Synthesis of ZnO nanometer powders doped with Ce4+ ions and the photocatalytic degradation of dying wastewater

Ce4+-doped nanometer ZnO powder was synthesized by so-l gel method. The microstructures and properties of the samples were characterized through XRD, UV-Vis and FTIR. The results indicated that the Ce4+ was successfully incorporated into ZnO, and the diameter of the nanometer was about 10.7nm. It induced the redshifting in the UV-Vis spectra. The photocatalytic activity of the samples was investigated using methylene blue (MB) as the model reaction under irradiation with ultraviolet light. The results showed that the doping of Ce4+ could increase the photocatalytic activities of ZnO nanopowders and that the best molar ratio of Ce4+ was n(Ce)/n(Zn) = 0.05, that the surfactant was sodium dodecyl sulfate, and that the nanometer ZnO was calcinated at 550 ℃ for 3 hours. Meanwhile, it inspected the effect of photocatalytic efficiency through the pH of MB, the amount of catalyst, and illumination time. The experimental results revealed that the initial mass concentration of MB was 10 mg/L, that the pH value was 7-8, that the dosage of Ce4+/ZnO photo-catalyst was 5 g/L, that the UV-irradiation time was 2 h, and that the removal rate of MB reached above 85%. Under the optimized conditions, the degradation rate of real dye wastewater was up to 87.67% and the removal efficiency of COD was 63.5%.

Influence of the shaker mill in the properties of ZnO processed by high energy milling

This work evaluates how the High Energy Ball Milling (HEBM) in a shaker mill influences the optical, physical, and microstructural properties of ZnO. The procedure also combines Fe inclusion from the grinding medium with particle size reduction. ZnO powder was milled by 1, 2, 3, 4, and 5 h, which resulted in a particle size reduction to the nanometric scale with a mean size of around 50 nm and a crystallite size reduction by three times when processed from 4 h. Milling has proven to be an efficient process for obtaining nanoparticles with an incredibly short processing time and changed the morphology of the particles from random to spherical shapes. Results also indicate the processing progressively expanded the ZnO hexagonal structure due to the imposed strain and Fe inclusion, which can help to decrease the bandgap and slow down the recombination rate of the electron-hole pairs, improving the photocatalysis activity. The optical results showed no additional band appeared due to milling processes and diminished the bandgap from 3.37 to 3.21 eV. Milling also led to an increase in the c value from 5.2076 to 5.2112 Å, which is one of the most important factors for improved antibacterial activity. HEBM has proved to be a suitable process for obtaining ZnO nanoparticles with properties useful for various applications.

Photocatalytic degradation of reactive black dye using ZnO – CeO2 Nanocomposites

Nano-CeO2 was synthesized via the chemical precipitation of cerium precursor solution, and then mixed with nano-ZnO at various weight ratios to obtain ZnO-CeO2nanocomposites. The composites were characterized for their morphological and photocatalytic properties. X-ray diffraction patterns of the pristine metal oxides corresponded well with (1 0 1) and (1 1 1) peaks of hexagonal wurtzite like-ZnO and cubic-phase CeO2, respectively. The band gap of the ZnO-CeO2nanocomposite was 3.08 eV, while that of pristine CeO2 and ZnO powder was 3.24 eV and 3.12 eV respectively. Photocatalytic activity of ZnO-CeO2composite was evaluated at various Reactive Black (RB) dye and catalyst concentrations. A 1:1 wt ratio ZnO-CeO2 nanocompsite provided the maximum (~ 85%) RB oxidation under UV light within 90 minutes. Rate of dye degradation obtained with ZnO-CeO2nanocomposite was almost 1.5 times more than that obtained with bare ZnO. It was observed that increase in CeO2 to ZnO ratio increased oxidation rates up to 1:1 wt ratio. Increasing CeO2 ratio beyond 1:1 wt. ratio did not significantly increase RB oxidation. The results confirm that addition of CeO2 to ZnO has resulted in lowering its bandgap energy and in-turn favors oxidation of RB dye under UV light.

FTIR study of ZnO powder prepared by self-combustion method at different temperature

Nowadays nanomaterial is used widely because of their change in characteristics from bulk to nano. In this paper the preparation of ZnO nano powder by self-combustion high temperature method was discussed. The solution of Zinc Nitrate as a precursor and dextrose as a fuel was kept in furnace at 400,500 and 600 0C for 5-15 minute to complete the reaction. The ZnO thick films were prepared by screen printing and fired at 650 0C. The effect of different synthesis temperature on ZnO thick films were study by FTIR analysis. The applications of zinc oxide powders were discussed in these papers.

Metal salts as dopants for ZnO ceramics-thermogravimetry coupled with mass spectrometry studies

The paper presents results concerning thermal decomposition of copper II salts (acetylacetonate, acetate monohydrate and nitrate trihydrate) in synthetic air and argon flow. Thermogravimetry tests coupled with mass spectrometry were performed in temperature range of 25–1300 °C. The influence of salt addition on the rheological properties and sintering behaviour of ceramic samples was then investigated. The microstructure evolution based on light and scanning electron microscopies coupled with stereological methods was described. The performed investigations revealed not only the differences in thermal decomposition of examined salts but also differences in the phenomena related to the oxidation and reduction processes of copper products. The atmosphere has also influenced the mechanisms of salts decomposition as well as further changes in decomposition products. Moreover, the presence of ZnO powder has changed the thermal decomposition process of copper II acetylacetonate. The investigations showed that acetates and nitrates can be efficient in homogeneous distribution of small amounts of metal additives in the ZnO-based suspensions. Higher concentrations of these type of salts lead to the increase of viscosity due to the fact that acetates and nitrates increase the ionic strength in the slurry. On the other hand, acetylacetonates do not disturb the stability of the slurries. However, they are characterized by low water solubility and thus homogenous distribution of small amount of these dopants is more difficult. The addition of copper increased the grain size of the sintered ZnO samples. The copper was not segregated at grain boundaries in the form of oxide, it diffused into ZnO matrix.

Effect of K2O/ZnO+CaO Ratio on Density, Glass Forming Ability, Crystallization of SiO2- Al2O3- ZnO- K2O- CaO Frites

The frites by mole fraction of 2.5 SiO2, 0.20 Al2O3, 0.15 B2O3, 0.15ZnO, 0.17K2O, 0.67CaO systems in three ratios of S including 0.37(denoted by F1frites ),0.31(F2), 0.24(F3) (S=K2O/CaO+ZnO) were studied. ZnO powder with 500 nm (N series) and >1μm sizes (F series) opted from the recycled Zn ingots dusts and commercially ZnO respectively, were used as the raw materials. By decreasing the S ratio, the Molar Volumes of frites were decreased, The glass transition ΔTg(=-154ºC), and the crystallization temperatures ΔTp (=+17ºC) values were decreased and increased respectively. It was shown that the GS (glass stability) values are independent of the Zinc Oxide's powder size, while the Molar Volumes of N series were lower than the F ones. The Zinc Silicate (Willemite) beside Anorthite and Parawollastonite phases were crystallized in the resulted glazes. The hardness values were in 700-850 Hv range, the transparency and whiteness were higher than 80 and 60 respectively.

Surface Topology of Zinc Oxide Powder Prepared by High Temperature Sol Gel Combustion Method

ZnO is most widely and most attractive element in today’s research. ZnO powder is not available naturally. The ZnO powder was prepared by different methods. Here in this paper the preparation of powder was discussed. The powder was prepared by high temperature sol gel combustion method. Here in this study selected temperature was 500 0C ± 10 0C. to form the pure ZnO powder the synthesized powder was sintered at 6500C ± 10 0C. After sintering the white ZnO powder was formed with amorous in nature.This method was easy and high yield. The powder was characterized by using XRD and SEM. From XRD grain size was calculated. Using SEM the particle size, specific surface area, surface roughness and the surface morphology was studied.