CdTe quantum dots capped with different stabilizing agents for sensing of ochratoxin A

Cadmium telluride (CdTe) quantum dots (QDs) were prepared from aqueous solution with different capping agents of thioglycolic acid (TGA) and L-cysteine. Photoluminance spectra of CdTe QDs were used as a property of optical sensor for ochratoxin A (OTA) in the concentration range of ng/mL. It was found that L-cysteine capped CdTe QDs have linear response to OTA concentration in the range from 0.5 to 10 ng/mL. By applying Stern-Volmer relationship, it was found that a very good linearity (R2=0.99) is observed in the concentration range from 0.5 to 10 ng/ml, Ksv was 3.48 ×104 L g−1 and the minimum of detection was 0.5 ng/ml. TGA capped CdTe QDs have a fair of linearity of R2 equals to 0.8929 in the concentration range from 5 to 30 ng/ml of OTA and Ksv was 1.4×105 L g−1 with the minimum of detection of 5 ng/ml. The mechanism of the effect of pH on the fluorescence of CdTe QDs was proposed and the low fluorescence intensity of CdTe QDs in acidic media was attributed to protonation of the surface binding thiolates and consequently the dissociation of CdTe QDs.