L- and D-cysteine Functionalized CdS Quantum Dots as Nanosensors for Detection of L-morphine and D-methamphetamine

A new method in differentiation of chiral molecules is reported based on the fluorescence quenching of functionalized CdS quantum dots (CdSQDs) as nanosensor by differing in the chirality of functionalization species. The chemically functionalized CdS-QDs with strong yellow emission were prepared using chiral L-cysteine (L-Cyst) and D-cysteine (D-Cyst) molecules. Then, the functionalized CdS-QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, photoluminescence (PL), ultraviolet-visible (UV-Vis), and Fourier transform infrared (FT-IR) spectroscopies. The prepared L- and D-cysteine functionalized CdS-QDs were exploited as fluorescence probes for detection and determination of L-morphine and D-methamphetamine. It was found that the fluorescence of D- and L-cysteine functionalized CdS-QDs were efficiently quenched by adding D-methamphetamine and L-morphine to them, respectively. The magnitude of fluorescence quenching depended on the concentration of L-morphine and D-methamphetamine solutions according to the Stern-Volmer equation. So, the functionalized CdS-QDs can be used as simple, quick, cheap, and sensitive nanosensor for practical detection of morphine and methamphetamine.