Morphology-tunable synthesis of ZnO nanoforest and its photoelectrochemical performance

Hierarchical nanostructures of metal oxides for enhancing charge separation and transport in photoelectrochemical solar energy conversion systems

Photoelectrochemical solar energy conversion systems, including photoelectrochemical water splitting and photoelectrochemical solar cells (dye-sensitized solar cells, DSSCs), are under intensive development aiming at efficiently harvesting and utilizing solar energy. Metal oxides carved into hierarchical nanostructures are thought to be promising for improving photoelectrochemical performance by enhancing charge separation and transport. Herein, we review the recent progress in the research on the design and applications of metal oxide hierarchical nanostructures in water splitting and DSSC systems with a view to understanding how they improve the device performance in terms of enhanced charge separation and transport properties. This review will end with a conclusion on metal oxide hierarchical nanostructures together with potential future research directions thereof.

Synthesis of ZnO nanowire arrays/3D graphene foam and application for determination of levodopa in the presence of uric acid

Three-dimensional (3D) graphene foam (GF) was prepared by chemical vapor deposition (CVD) using nickel foam as the template. ZnO nanowire arrays (ZnO NWAs) were vertically grown on the 3D GF by hydrothermal synthesis to prepare ZnO NWAs/GF. This hybrid combines the properties of ZnO NWAs and 3D GF, which has favorable electrocatalysis and outstanding electrical conductivity. The vertically aligned ZnO NWAs grown on the GF enlarged the electroactive surface area, which was investigated from the Fe(CN)₆^3-4+ redox kinetic study. The ZnO NWAs/GF was used as an electrochemical electrode for the determination of Levodopa (LD) in the presence of uric acid (UA). The electrochemical responses of the ZnO NWAs/GF electrode were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the sensitivity of the electrode for LD is 3.15μAμM^-1 in the concentration range of 0.05-20μM and the measured detection limit of the electrode for LD is 50nM. The electrode also shows good selectivity, reproducibility and stability. The proposed electrode is succsefully used to determine LD in human plasma samples and it is potential for use in clinical research.

An overview on emerging photoelectrochemical self-powered ultraviolet photodetectors

In recent years, as a new member of ultraviolet photodetectors (UV-PDs), photoelectrochemical UV-PDs (PEC UV-PDs) have received great attention. Compared to conventional photoconductors, PEC UV-PDs exhibit a number of merits, including low cost, environmentally friendly nature, being self-powered, and fast response. This tutorial review provides a comprehensive introduction to this research field, covering from the basics of performance evaluation of PEC UV-PDs, the state-of-the-art advances in structural design, electrolyte matching, and electrode fabrication of PEC UV-PDs, to the integration of multiple functions into a PEC UV-PD. In the end, we present our perspectives on the future development of PEC UV-PDs and highlight the key technical challenges in aiming to stimulate further developments in this research field.

Synthesis of Various ZnO Nanotree Morphologies through PEG-Assisted Co-Precipitation Method

ZnO, with direct wide band gap of 3.37 eV and high excitonic binding energy of 60 meV has been attracting much attention due to its wide range of applications, for transparent electronics, solar cells, and other optoelectronics device. We present a simple, single step process to produce ZnO nanotrees using co-precipitation method. As a precursor, zinc nitrate dehydrate was stabilized by hexamethylene tetraamine (HMTA) and 3-9 mM polyethylene glycol (PEG) was added at 180°C for 3-6 hours followed by residual polymer removal. Scanning Electron Microscopy revealed the typical rod-like branched nanostructures were achieved. For longer annealing time the PEG-assisted growth process indeed exhibited a distinctive c-direction inhibition responsible for the lateral growth and subsequent branching of ZnO, in which the branch growth in sample with PEG amount of 0.05 g is the slowest. Some amounts of PEG up to 0.03 g are sensitive to affect several parameters, such as, lattice stress, unit cell volume, density of film and dislocation density.

Selective recognition of hydrogen sulfide using template and catalyst free grown ZnO nanorods

A single step spray pyrolysis technique was used to grow ZnO nanorods on glass substrates without any template or catalyst and the nanorods were successfully employed to detect hydrogen sulfide at room temperature.

Coalescence of ZnO nanowires grown from monodisperse Au nanoparticles

The coalescence of ZnO nanowires grown from monodisperse Au nanoparticles was investigated by correlative imaging techniques and modelling.

State of the art of nanoforest structures and their applications

Forest-like nanostructures, their syntheses, properties, and applications are reviewed.

A simple and template free synthesis of branched ZnO nanoarchitectures for sensor applications

Branched ZnO nanoarchitectures synthesized by a simple chemical technique and used as a room temperature acetaldehyde sensor.