Synthesis and Growth Kinetics of Zns and Cds Quantum Dots Via Reverse Micelles

Natacha Souto1, Julio G. Briano1, and Roberto Irizarry2. (1) Chemical Engineering, University of Puerto Rico, Mayaguez Campus, Mayaguez, PR 00680, (2) Electronic Technologies, DuPont, 14 TW Alexander Drive, Research Triangle Park, Raleigh, NC 27709

Semiconductor nanomaterials (quantum dots), have attracted the interest of the scientific community in recent years, because of their unique properties. Some potential applications may be found in areas such as photocatalysis, solar cells, as a pigment or in electroluminescence panels. Two key factors, quantum confinement effect, and surface effects determine the optical properties of nanoparticles. Due to quantum confinement, nanoparticles have moleculelike discrete energy spectra. Consequently, the position of the absorption peak corresponding to the first electronic transition of the exciton is strongly size dependent. This work is focused on the synthesis of nanoparticles of CdS CdSe ZnS and ZnSe via AOT reverse micelles. The growth process at the concentration level used, last a few seconds, and was monitored on line by absorption spectroscopy. The size increase was directly related to the displacement of the energy gap. To avoid mass transfer effects, a stopped flow reactor was used. It is interesting to mention that the first stages of the growth process (times shorter than 0.1s) gave us an idea of the growth mechanism. Agglomeration was evident after a few seconds of the process.