Narrow Results

Zinc oxide (ZnO) and yttrium-doped ZnO nanoparticles with particle size in the nanometer range have been successfully synthesized by the alkali precipitation method. The nanoparticle size and morphology have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The average particle size of Y-doped ZnO nanoparticles is about 17–29 nm. The absorption and photoluminescence (PL) spectra of the undoped and doped ZnO nanoparticles were also investigated. The optical band gap of ZnO nanoparticles can be tuned from 3.27 to 3.40 eV with increasing yittrium doping levels from 0 to 5%. The nanoparticles gave two emission peaks, one at around 376 nm and the other at 500 nm.

A new method for preparation of a carbon nanotube (CNT)–zinc oxide hybrid on a glass substrate at low temperature is introduced and the stability improvement of field emission of CNTs is reported. The emission current stability and substrate material are the two main commercial parameters for field emission applications of CNTs. The two alternative current (AC) and direct current (DC) plasma enhancement chemical vapor deposition (PECVD) is used to achieve low-temperature growth of vertically aligned CNTs and the hydrothermal processing is used for production of zinc oxide nanowires to improve the emission current stability and properties. The nanoscale junction between a semiconductor and conductive material are critical for electronic applications. The present study examined the field emission properties of CNTs near the crystalline structure of the zinc oxide hybrids and showed the improvement in the field enhancement factor and emission current stability of CNT–ZnO hybrid than the CNT emitters.

In this paper, we prepared the rattle type nanoparticles ZnO@void@SiO₂ by two successive coating processes, followed by heat treatment. The carbon layer was formed over ZnO surface with the aid of the hydrothermal treatment of glucose. Then the resulting composite was used to fabricate a silica shell on the surface by sol–gel method. Finally, ZnO particles were released but still trapped inside the silica hollow after calcination, that is, ZnO@void@SiO₂. The composites were characterized by scanning and transmission electron microscope, N₂ adsorption experiment, X-ray diffraction, Fourier transform infrared spectroscopy and UV-Vis absorption spectra. The rattle type structure was conformed and the sphere-like structure with the average size of 70 nm and hexagonal wurtzite crystal structure were also observed. The measurement results of optical properties showed even though ZnO@C@SiO₂ presented no photocatalysis, ZnO@void@SiO₂ showed high activity even the ZnO core was encapsulated with the SiO₂ hollow.

In this work, we report theoretical and experimental study of Pd/ZnO nanorod (NR) Schottky diodes-based ultraviolet photodetector (UV-PD). The ZnO-NRs are deposited on indium tin oxide (ITO) coated glass substrates by using a low-temperature hydrothermal method. The surface morphology of the ZnO-NRs film is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SEM image shows vertically grown NRs with uniformity, and XRD shows the preferred (002) orientation of ZnO-NR films. The current–voltage characteristics of Pd/ZnO-NR Schottky diodes are studied under dark and UV light. A voltage bias from $-$1V to $+$1V is applied and the ratio of photocurrent to dark current was ($\sim 0.17\times 10^2$ at $V=0.5$V) calculated from the $I$–$V$ curve. The value of responsivity was found to be 0.111A/W at $\lambda =365$nm and at $\mathrm{\text{bias}}=0.50$V. An approximated UV-PD structure has also been numerically simulated using three-dimensional (3D) device simulator from Visual TCAD of Cogenda International. The simulated $I$–$V$ characteristics have also been plotted under both dark and light conditions. The simulated results are found to be following the nature of experimental results.

Photoelectrochemical (PEC) sensor is an important type of biosensor widely used in glutathione (GSH) sensing. The PEC properties of the photoanode present in the sensor are critical to its sensing performance. Zinc oxide (ZnO) is an excellent semiconductor with a suitable band gap and light absorption ability for photoanode applications. Meanwhile, the interfacial layer is also important in the separation and transportation process of the excitons. In this work, high-quality ZnO nanorods were grown on the indium tin oxide (ITO) substrates. An interfacial layer consisting of reduced graphene oxide (RGO) or MXene (a two-dimensional transition metal carbide)-derived TiO₂ was introduced. Our results show that the introduction of the RGO/TiO₂ hybrid interfacial layer can promote both the high-quality growth of ZnO nanorods and also provides suitable band gap grading for efficient excitons separation and transportation. The GSH sensing performance of the PEC sensor based on the ZnO nanorods grown on the RGO/TiO₂ hybrid layer-coated ITO photoanode can dramatically improve the photocurrent strength and linearity.

Novel Cu-based binary composite phases were synthesized with an octadecylamine (ODA) synthetic system. HR-TEM was used to characterize the binary composite phase indicating that the Cu-based binary composite phase was a mixed phase of two oxides. ZnO gas sensing films decorated with Cu-based binary composite phase were parallel fabricated. The gas sensing performance to nitric oxides (NO, N₂O, NO${}_2)$ was studied. Cu–Mo–O binary composite phase-modified ZnO was screened out with high sensitivity and selectivity to NO. The gas sensing response to 0.5 ppm NO was 128.1. The detection limit of Cu–Mo–O binary composite phase-modified ZnO to NO was less than 10 ppb. Cu–Mo–O binary composite phase-modified ZnO also shows good selectivity to NO even using NO₂ as interference gas. It is of great importance for the detection of NO.

Selaginella willdenowii, a commonly used greenhouse fern, was often used as a biowaste to synthesize zinc oxide nanoparticles (ZnO NPs) in an eco-friendly and cost-effective way. UV–Visible spectra studies were carried out to confirm the synthesis of S. willdenowii-mediated ZnO NPs (SW-ZnO NPs), and a peak at 367nm with a sharp band gap of 3.415eV was observed. The X-ray diffraction analysis indicated that the crystalline size of the synthesized SW-ZnO NPs was 11.971nm. The phytochemicals present in the extracts and the compounds involved in the reduction of metal to nanoparticles were determined by Fourier Transform Infrared analysis. Scanning electron microscopy was utilized to analyze the surface morphology and size of the obtained SW-ZnO NPs. The examination revealed that they exhibited a hexagonal shape, with an average size falling within the range of 17–23nm. Under ultra-violet light, reactive blue 220 and reactive yellow 145 dyes showed 78.06% and 60.14% degradation, showing potential photocatalytic degradation activity. The synthesized SW-ZnO NPs also exhibited antimicrobial activity against bacterial strains (Escherichia coli and Bacillus subtilis) and fungal cultures (Candida tropicalis and Candida albicans) showed cytotoxic activity against Hep-G2 cell lines. Our results suggest the green synthesized SW-ZnO NPs have potential photocatalytic, antimicrobial and cytotoxic potential.