Reduction of the photocatalytic activity of ZnO nanoparticles for UV protection applications

The detrimental effects of UV radiation are having a significant impact on our life and environment. The development of effective UV shielding agents is therefore of great importance to our society. ZnO nanoparticles are considered to be one of the most effective UV blocking agents. However, the development of ZnO-based UV shielding products is currently hindered due to the adverse effects of the inherent photocatalytic activity exhibited by ZnO. This paper reports our recent study on the possibility of reducing the photoactivity of ZnO nanoparticles via surface modification and impurity doping. It was found that the photoactivity was drastically reduced by SiO2-coatings that were applied to ZnO quantum dots using the Stöber method and a microemulsion technique. The effect of transition metal doping on the photoactivity was also studied using mechanochemical processing and a co-precipitation method. Cobalt doping reduced the photoactivity, while manganese doping led to mixed results, possibly due to the difference in the location of dopant ions derived from the difference in the synthesis methods.

Emission-based condition monitoring technique for ZnO surge arrester

In this paper, electromagnetic emission at the frequency range of 30MHz to 300MHz is used to detect physical defects on the 22kV outdoor zinc-oxide (ZnO) surge arresters. Different weather conditions combining with artificially created pollution were produced in a laboratory environment and measurements were recorded over a fixed period of time. Pollution due to fine dust particles has been created according to IEC standard under both wet and dry conditions. The aim is to detect the defects (bushing damage) when the surge arrester is subjected to various weather and surface condition. The collected electromagnetic signals were sampled and analyzed using analysis tools such as the autocorrelation coefficient and Wigner-Ville distribution. The results from the present paper indicate that electromagnetic radiation from the defects on surge arrester combining with the adequate analysis tools can be used as a valuable diagnostic tool for power system operator.

Latex-based nanocomposites

Nanoparticles have been widely used as filler in polymer because of their unique reinforcing effect. There are many compounding methods for nanocomposites. The recent development on latex nanocomposites, a group of special nanocomposites, is reviewed in this chapter. They include carbon black/latex nanocomposite, silica/latex nanocomposite, layered silicate/latex nanocomposite, ZnO/latex nanocomposite, carbon nanotubellatex nanocomposite, lignin/latex nanocomposite, starch/latex nanocomposite, nano-fiber/latex nanocomposite, and Chitin whiskers/latex nanocomposite. Advanced compounding techniques and the latest advance on these latex nanocomposites are described. The nanoreinforcing theories of latex nanocomposites are also studied.

Synthesis of silica-coated ZnO nanocomposite : the resonance structure of polyvinyl pyrrolidone (PVP) as a coupling agent

Abstract The preparation of silica-coated ZnO nanocomposite using polyvinyl pyrrolidone (PVP) as a coupling agent was investigated. Transmission electron microscopy analysis revealed that silica has been deposited on the surface of PVP-capped ZnO nanoparticles as a continuous thin layer. Two-dimensional correlation analysis based on the time-dependent UV–vis spectra was introduced to study the interaction governing the deposition of silica on to PVP-capped ZnO. Strong hydrogen bonds formed between the amphiphilic PVP molecules and silica in the silicacoated PVP-capped ZnO composites. The reduced photocatalytic activity of silica-coated ZnO nanoparticles will enhance their performance as durable, safe, and nonreactive UV blockers in plastics, paints, and coating for outdoor textile and timber products.