Metal oxide nanostructures synthesized on flexible and solid substrates and used for catalysts, UV detectors and chemical sensors

In this paper we demonstrate the visibility of the low temperature chemical synthesis for developing device quality material grown on flexible and solid substrates. Both colorimetric sensors and UV photodetectors will be presented. The colorimetric sensors developed on paper were demonstrated for heavy metal detection, in particular for detecting copper ions in aqueous solutions. The demonstrated colorimetric copper ion sensors developed here are based on ZnO@ ZnS core-shell nanoparticles (CSNPs). These sensors demonstrated an excellent low detection limit of less than 1 ppm of copper ions. Further the colorimetric sensors operate efficiently in a wide pH range between 4 and 11, and even in turbulent water. The CSNPs were additionally used as efficient photocatalytic degradation element and were found to be more efficient than pure ZnO nanoparticles (NPs). Also p-NiO/n-ZnO thin film/nanorods pn junctions were synthesized by a two-step synthesis process and were found to act as efficient UV photodetectors. Additionally we show the effect of the morphology of different CuO nanostructures on the efficiency of photo catalytic degradation of Congo red organic dye

Colorimetric Disposable Paper Coated with ZnO@ZnS Core-Shell Nanoparticles for Detection of Copper Ions in Aqueous Solutions

In this study, we have proposed a new nanoparticle-containing test paper sensor that could be used as an inexpensive, easy-to-use, portable, and highly selective sensor to detect Cu2+ ions in aqueous solutions. This disposable paper sensor is based on ZnO@ZnS core-shell nanoparticles. The core-shell nanoparticles were synthesized using a chemical method and then they were used for coating the paper. The synthesis of the ZnO@ZnS core-shell nanoparticles was performed at a temperature as low as 60 degrees C, and so far this is the lowest temperature for the synthesis of such core-shell nanoparticles. The sensitivity of the paper sensor was investigated for different Cu2+ ion concentrations in aqueous solutions and the results show a direct linear relation between the Cu2+ ions concentration and the color intensity of the paper sensor with a visual detection limit as low as 15 mu M (similar to 0.96 ppm). Testing the present paper sensor on real river turbulent water shows a maximum 5% relative error for determining the Cu2+ ions concentration, which confirms that the presented paper sensor can successfully be used efficiently for detection in complex solutions with high selectivity. Photographs of the paper sensor taken using a regular digital camera were transferred to a computer and analyzed by ImageJ Photoshop software. This finding demonstrates the potential of the present disposable paper sensor for the development of a portable, accurate, and selective heavy metal detection technology.Funding Agencies|Shahid Chamran University; Linkoping University</p