Design of NiS@NiS/CdS heterostructure with intimate contact interface for sensitive photoelectrochemical detection of lincomycin.

Owing to their internal electric field effect and abundant photo-induced carriers, photoactive heterostructured materials are considered a feasible approach to improve the sensitivity of a photoelectrochemical (PEC) sensor. Herein, a novel NiS@NiS/CdS heterostructure composite is derived from Ni-loaded zeolitic imidazolate framework (Ni-ZIF). The PEC experiments showed the NiS@NiS/CdS composite exhibits superior photocurrent response than NiS@NiS and CdS. This is attributed to the fact that the type II heterojunction of NiS@NiS/CdS with a tightly connected interface reduces the transport distance of carriers and facilitates electron-hole separation. Next, using the NiS@NiS/CdS modified electrode, an aptamer/glutaraldehyde/chitosan/NiS@NiS/CdS/ITO PEC biosensor is developed, which exhibits excellent sensitivity for lincomycin (Lin) detection with a wide linear range (0.0001 ∼ 1.25 nM) and a low detection limit of 0.067 pM. The prepared sensor is further employed to monitor Lin in the actual milk. The results confirm that the prepared sensing electrode displays good selectivity, repeatability and stability.