Nanocomposite optosensor of dual quantum dot fluorescence probes for simultaneous detection of cephalexin and ceftriaxone

An optosensor based on the fluorescence quenching of two different nanocomposite fluorescence probes was developed for simultaneous detection of cephalexin and ceftriaxone. The nanocomposite fluorescence probes were synthesized by incorporating graphene quantum dots (GQDs) and cadmium telluride quantum dots (CdTe QDs) in a molecularly imprinted polymer (MIP). The MIP-GQDs and MIP-CdTe QDs exhibited high emission fluorescence intensities at 440 and 575 nm, respectively. The mesoporous structure of the MIP layer provided recognition sites specific to the template analytes. At the optimum condition, the fluorescence intensities of the probes were quenched linearly as the concentrations of cephalexin and ceftriaxone increased from 0.10 to 50.0 mu g L-1. The very low detection limits were 0.06 and 0.10 mu g L-1 for cephalexin and ceftriaxone, respectively. The developed dual nanocomposite fluorescence probes were used for the detection of cephalexin and ceftriaxone in milk samples. The recoveries of cephalexin and ceftriaxone in four spiked milk samples ranged from 83.0 to 98.7% with RSD lower than 8%. This developed nanocomposite optosensor was highly sensitive and selective for trace detection of cephalexin and ceftriaxone in milk samples and produced results that were in good agreement with the results of HPLC analysis of the same samples.