Nano-sized semiconductor CdS covered with a carboxyl group was prepared in an aqueous solution and demonstrated to be applicable as a fluorescent probe. Amino-modified latex beads or those mixed with CdS without surface modification could not detect any luminescence. On the other hand, those attached to the CdS with carboxyl group were distinct the fluorescent images. It suggests that the carboxyl group capped CdS particle can be used as a fluorescent probe.
