Effect of phenylalanine on photoluminescence and stability of CdTe nanocrystals capped with thioglycolic acid

CdTe nanocrystals capped with thioglycolic acid in aqueous were conjugated with phenylalanine (Phe) in order to study the effect of Phe on the photoluminescence (PL) and stability of CdTe nanocrystals. The PL intensity of CdTe–Phe conjugate has enhanced greatly comparing with CdTe nanocrystals due to the interaction of CdTe and Phe. This interaction of Cd ion on the surface of CdTe nanocrystals with carboxyl group of Phe was identified by IR, TEM and PL spectra analyses. The effect of the reflux time, pH and the ratio of CdTe nanocrystals to Phe were also investigated. The results showed that Phe could prevent the aggregation of CdTe nanocrystals beside thioglycolic acid as a capping reagent of CdTe nanocrystals. The coordination between Phe and CdTe nanocrystals resulted in increasing both the PL intensity and the stabilization of CdTe–Phe conjugate. Furthermore, the phenyl group of Phe delayed the photo-oxidation of both CdTe nanocrystals and thiol ligands on the surface of CdTe nanoparticles. The pH value of the reaction system was an important factor for the reaction of CdTe nanocrystals and Phe because of the amphoteric property of Phe. The results of this paper was useful to understand the mechanism of the reaction between nanocrystals such as CdTe, CdSe, CdS and peptides or protein such as antibodies and enzymes composed of Phe or other apolar amino acids.