Direct Synthesis of Water-Soluble Ultrathin CdS Nanorods and Reversible Tuning of the Solubility by Alkalinity

Highly water-soluble ultrathin and fluorescent CdS nanorods are directly synthesized with the assistance of PEI. PEI plays as the passivator to control and induce the growth of the US nanorods and also makes the as obtained nanorods dispersible in water. The as-obtained US nanorods are quite thin thus showing the quantum effect in the fluorescence. By adjusting the alkalinity of the solution. US nanorods can be controlled to precipitate or redisperse in water, which is believed to stern from the variation of the charges of the capping PE:1 molecules. These results provide an efficient and convenient way to directly synthesize water-soluble and fluorescent nanocrystals, which has potential application in biological labeling and detection.