Designed self-assembled hybrid Au@CdS core-shell nanoparticles with negative charge and their application as highly selective biosensors.

A novel and general strategy for the synthesis of a monodispersed Au@CdS core-shell structure with uniform morphology and size through a self-assembly process is proposed here. The obtained negatively charged Au@CdS hybrid core-shell nanoparticles (NPs) are highly selective to dopamine (DA), in the presence of oxidation of ascorbic acid (AA) and uric acid (UA), based on electrostatic interaction. The fabricated biosensor shows a wide linear range from 0.002 to 800 μmol L-1, with a lower detection limit of 0.55 nmol L-1 (n = 5, S/N = 3), revealing the high-sensitivity properties. Electrostatic charge plays an important role in the selective electrocatalytic activity of Au@CdS hybrid core-shell nanoparticles, that is the formation of an electrostatic system between the negatively charged Au@CdS hybrid core-shell NPs and the DA cation. The modified electrode is used to achieve the real-time quantitative detection of DA for biological applications, and satisfactory results are obtained. Due to the advantages of the biosensor, its selectivity, sensitivity and stability, it will have a bright future in the field of medical diagnosis.