ABSORPTION AND FLUORESCENCE BEHAVIOR OF REDISPERSIBLE CDS COLLOIDS IN VARIOUS ORGANIC-SOLVENTS

For the first time, redispersible CdS colloids with a narrow size distribution were prepared which readily dissolve in a wide range of polar and nonpolar organic solvents. The absorption and fluorescence properties of these CdS colloids stabilized with sulfonic acids were studied as a function of both the dielectric constant and hydrogen bonding ability of the solvent. The absorption spectra of the CdS colloids, reflecting their particle size distribution, are not affected by the solvent, but their fluorescence behavior is strongly solvent dependent. In protic solvents, only trapped emission is observed whereas both excitonic and trapped fluorescence occur in aprotic solvents, the intensity of the emission depending on the dielectric constant of the aprotic solvent. Furthermore, the sulfonic acid bound to the CdS particle surface could be exchanged for other stabilizers such as polyphosphate, silicate, 2-mercaptoethanol, 3-mercapto-1,2-propanediol, and benzenethiol. Stabilizer exchange drastically changes the solubility and the fluorescence of the CdS particles but has no significant effect on their absorption spectra.