Zinc oxide (ZnO) is considered a workhorse of technological development exhibiting excellent electrical, optical, and chemical properties with a broad range of applications as semiconductors, in optical devices, piezoelectric devices, surface acoustic wave devices, sensors, transparent electrodes, solar cells, antibacterial activity etc. Thin films or nanoscale coating of ZnO nanoparticles on suitable substrates are viewed with great interest for their potential applications as substrates for functional coating, printing, UV inks, e-print, optical communication (security-papers), protection, barriers, portable energy, sensors, photocatalytic wallpaper with antibacterial activity etc. Various methods like chemical, thermal, spin coating, spray pyrolysis, pulsed laser deposition have been used for thin film formation but they are limited to solid supports such as metal, metal oxides, glass or other thermally stable substrates. Coating of ZnO nanoparticles on thermolabile surfaces is scarce and coating on paper was yet to be reported. Paper as a substrate is an economic alternative for technological applications having desired portability and flexibility. Researchers from the National Tsing Hua University in Taiwan found a way of coating paper with ZnO nanoparticles using ultrasound.
Professor Yong-Chien Ling, who led the research team, explained the recent findings to Nanowerk: "Our work presents for the first time a simple, green, and cost-effective way of coating ZnO nanoparticles on a paper surface (thermolabile substrate) without the use of binders."
Existing coating techniques for paper, especially the contact mechanical ones, can cause surface defects, variable layer thickness and composition, consume more material by filling fiber interstices and need excess solvent and energy. Therefore non-impact, spray-based techniques are generally preferred but they are costly, require more maintenance and consume even more solvent medium.
Coating on the nanoscale would enable improved techniques that consume less material. Furthermore, with increased emphasis on green chemistry, interest has been developed towards adoption and implementation of sustainable processes by minimizing the use of toxic chemicals, solvents, and energy.
"This led us to conclude that development of a nonimpact coating technique on the verge of green chemistry and nanoscience is crucial for revitalizing coating progress through nanostructuring" says Ling.
Read the full article on the Nanowerk website.
Nanowerk is a leading nanotechnology information portal. Apart from its unique Nanomaterial Database™, with over 1,300 products from 90 suppliers, it provides the most complete nanotech events calendar; hundreds of links to universities, labs, researchers, associations, networks and international initiatives involved in nanotechnology; daily news; downloadable reports; and much more. The site includes a daily “Spotlight” section featuring Nanowerk-exclusive reviews and summaries of cutting-edge nanotechnology research by guest authors and Nanowerk editors. Nanowerk also publishes the nanoRISK newsletter – a constructive contribution to the debate about the potential risks of nanotechnology.
By Michael Berger, Copyright 2006 Nanowerk LLC