In this paper, a novel method was developed for rapid and quantitative determination of cephalexin on the basis of the fluorescence quenching of L-cysteine capped core–shell CdTe/ZnS nanoparticles (NPs). The functionalized CdTe/ZnS NPs were successfully synthesized in aqueous solution. L-Cysteine capped CdTe/ZnS NPs were characterized by the means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Experimental results displayed that the fluorescence intensity of CdTe/ZnS NPs reduced in the presence of cephalexin due to interaction between L-cysteine capped CdTe/ZnS NPs and cephalexin, with the emission wavelength at about 665 nm. Under optimal conditions, the relative fluorescence intensity was linearly proportional to the concentration of cephalexin ranging from 3.4 × 10−6 to 1.0 × 10−4 M with a detection limit of 0.83 × 10−6 M. The L-cysteine capped CdTe/ZnS NPs fluorescence probe showed an obvious and good response to cephalexin, and the result was also satisfactory when it was applied to analyzing cephalexin in a real sample.
