Design and Development of Inexpensive Paper-Based Chemosensors for Detection of Divalent Copper.

Simple, portable, and low-cost paper-based sensors are alternative devices that have the potential to replace high-cost sensing technologies. The compatibility of the paper base biosensors for both chemical and biochemical accentuates its feasibility for application in clinical diagnosis, environmental monitoring, and food quality monitoring. High concentration of copper in blood serum and urine is associated with diseases like liver diseases, carcinomas, acute and chronic infections, rheumatoid arthritis, etc. Detection of copper concentration can give an early sign of Alzheimer disease. Apart from that genetic Wilson's disease can be detected by evaluating the concentration of copper in the urine. In view of the above advantages, a novel and the highly sensitive paper-based sensor has been designed for the selective detection of Cu2+ ions. The fast and highly sensitive chemiresistive multi-dye system sensor can detect Cu2+ ions selectively in as low as 2.23 ppm concentration. Least interference has been observed for counter ion in the detection of Cu2+. Copper chloride, nitrate, and acetate were used to validate the detection process. This assay provides a very high selectivity of Cu2+ ion over other metal cations such as Na+, Mg2+, Ca2+, etc. The easy preparation and high stability of dye solutions, easy functionalization of the paper-based sensors, high selectivity over other cations, low interference of counter anion, and significantly low detection limit of 2.23 ppm make it an effective Cu2+ ion sensor for real-time application in near future.

Enhanced catalytic activity and near room temperature gas sensing properties of SnO2 nanoclusters@mesoporous Sn(iv) organophosphonate composite.

A simple, facile and one-pot route for preparing SnO2 nanoclusters embedded on a mesoporous Sn(iv) organophosphonate (MSnP) framework is described. Reaction of SnCl4·5H2O with a flexible tris-phosphonic acid, mesityl-1,3,5-tris(methylenephosphonic acid), in the presence of a surfactant under hydrothermal conditions produced the desired nanocomposite, SnO2@MSnP. Analytical, spectroscopic and microscopic studies establish that SnO2@MSnP composite is comprised of SnO2 nanoparticles of an average size of 5 nm evenly and abundantly dispersed over the MSnP framework. The mesoporous metal organophosphonate support significantly augments the catalytic efficacy and vapor sensitivity of SnO2 nanoparticles. The catalytic efficiency of SnO2@MSnP was tested for two acid-catalyzed reactions: deoximation reaction and esterification of fatty acids. SnO2@MSnP exhibits remarkable sensitivity towards ammonia and acetone vapors at near room temperature and under open atmospheric conditions. The present method represents an important step towards preparation of mesoporous metal organophosphonate supported metal oxide nanoclusters and hence offers easy access to functional metal oxide based nanocomposites.