Procedures for controlling the size, structure and optical properties of CdS quantum dots during synthesis in aqueous solution.

We report an easy approach for the synthesis of CdS Quantum Dots (CdS QDs) with high luminescence and temporal stability through the reaction of Cd(2+) and S(2-) in the presence of mercaptoacetic acid (MAA) as a capping reagent in aqueous medium, under normal pressure and room temperature. The influence of several experimental variables, including temperature, pH, the Cd/S ratio and the Cd/MAA ratio, on the optical properties of the QDs obtained was studied systematically. The experimental results indicate that these variables play an important role in determining the size and state of the surface of the nanoparticles, and hence their luminescent properties and temporal stability.

A gas diffusion technique coupled with flow injection systems. Optimization of the process in its application to the fluorimetric determination of ammonium in water samples.

A novel flow injection-gas-diffusion (GD-FI) system has been developed for the on-line analysis of ammonium ion in waters with fluorimetric detection, using an acceptor solution containing the Eosin-Bluish (EB) acid-base indicator. This, together with optimization of the process of gas transfer through the membrane, increases the sensitivity of the method to a considerable extent. Under optimum conditions, it is possible to determine the analyte within the 0.