Virgin silver nanoparticles as colorimetric nanoprobe for simultaneous detection of iodide and bromide ion in aqueous medium.

A simple colorimetric nanoprobe based on virgin silver nanoparticles (AgNPs) was developed for the selective detection of iodide and bromide ions via aggregation and anti-aggregation mechanism. With addition of I(-) ions, virgin AgNPs, in presence of Fe(3+), showed perceptible color change from yellow to colorless along with disappearance of surface plasmon resonance (SPR) band of AgNPs at 400 nm. But in presence of Cr(3+), AgNPs turned yellow upon addition of I(-)and Br(-) anions. The developed virgin AgNPs probe showed high specificity and selectivity with the detection limits down to 0.32 µM and 1.32 µM for I(-) ions via two different mechanistic routes. Also, the designed probe detects Br(-) with a detection limit down to 1.67 µM.

Precipitation of nanocrystalline CeO2 using triethanolamine.

Synthesis of cerium oxide nanocrystallites via precipitation using triethanolamine is reported. The molecular water associated with the cerium nitrate precursor is exploited to generate hydroxyl ions with the help of triethanolamine, facilitating precipitation. The small crystallite diameter (3 nm) in the as prepared powder is believed to result from the limited amount of water present. Solvent type has no effect on the final crystallite size or structure; however, it plays an important role in the dispersion of the nanoparticles with dispersity of the particles increasing with increasing carbon chain length of the solvent alcohol used.

Flame synthesis of nanosized Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts for the water-gas shift (WGS) reaction.

A flame synthesis method has been used to prepare nanosized, high-surface-area Cu-Ce-O, Ni-Ce-O, and Fe-Ce-O catalysts from aqueous solutions of metal acetate precursors. The particles were formed by vaporization of the precursors followed by reaction and then gas to particle conversion. The specific surface areas of the synthesized powders ranged from 127 to 163 m(2)/g. High-resolution transmission electron microscope imaging showed that the particle diameters for the ceria materials are in the range of 3-10 nm, and a thin layer of amorphous material was observed on the surface of the particles. The presence and surface enrichment of the transition-metal oxides (CuO, NiO, and Fe(2)O(3)) on the ceria particles were detected using X-ray photoelectron spectroscopy. Electron energy-loss spectroscopic studies suggest the formation of a core-shell structure in the as-prepared particles. Extended X-ray absorption fine structure studies suggest that the dopants in all M-Ce-O systems are almost isostructural with their oxide counterparts, indicating the doping materials form separate oxide phases (CuO, Fe(2)O(3), NiO) within the host matrix (CeO(2)). Etching results confirm that most of the transition-metal oxides are present on the surface of CeO(2), easily dissolved by nitric acid. The performance of the flame-synthesized catalysts was examined toward water-gas shift (WGS) activity for fuel processing applications. The WGS activity of metal ceria catalysts decreases in the order Cu-Ce-O > Ni-Ce-O > Fe-Ce-O > CeO(2) with a feed mixture having a hydrogen to carbon monoxide (H(2)/CO) ratio of 1. There was no methane formation for these catalysts under the tested conditions.