Surface-modified CdS nanoparticles as a fluorescent probe for the selective detection ofcysteine

Abstract

We present a novel method for the selective detection of cysteine, a sulfur-containing aminoacid, which plays a crucial role in many important biological functions such as proteinfolding. Surface-modified colloidal CdS nanoparticles have been used as a fluorescentprobe to selectively detect cysteine in the presence of other amino acids in themicromolar concentration range. Cysteine quenches the emission of CdS in the0.5–10 µM concentration range, whereas the other amino acids do not affect its emission. Among the otheramino acids, histidine is most efficient in quenching the emission of the CdS nanoparticles.The sulfur atom of cysteine plays a crucial role in the quenching process in the0.5–10 µM concentration range. Cysteine is believed to quench the emission of the CdS nanoparticlesby binding to their surface via its negatively charged sulfur atom. This method canpotentially be applied for its detection in biological samples.