An ultrasensitive photoelectrochemical immunosensor for insulin detection based on BiOBr/Ag2S composite by in-situ growth method with high visible-light activity

A novel ultrasensitive label-free immunosensor based on BiOBr/Ag2S composite with high visible-light photoelectrochemical activity was prepared for the detection of insulin. After BiOBr was modified by thioglycolic acid, Ag2S nanoparticles were grown in-situ on the surface of BiOBr hierarchical microspheres to first form novel BiOBr/Ag2S composite. When ascorbic acid (AA) was used as an efficient electron donor for scavenging photo-generated holes, BiOBr/Ag2S composite material showed excellent photoelectrochemical activity. In order to immobilize insulin antibody, adhesive polydopamine (PDA) film formed by self-polymerization of dopamine was fabricated onto BiOBr/Ag2S modified electrode. Moreover, PDA film could further enhance the visible light absorption of BiOBr/Ag2S. When the solutions of 0.08 mol L-1AgNO3 and 0.1 mol L-1 AA were selected respectively during fabrication and detection process of this sensor, the best photocurrent singles were obtained. Under the optimum experimental condition, the specific binding between insulin and antibody resulted in a decrease in photocurrent intensity and the intensity decreased linearly with the logarithm of insulin concentration in the range of 0.001-20 ng mL(-1) with a detection limit of 0.2 pg mL(-1). The photoelectrochemical sensor ITO/BiOBr/Ag2S/PDA/anti-Insulin/BSA/Insulin revealed facile preparation, high sensitivity, and acceptable reproducibility, which may have practical applications in the biosensor, clinical diagnosis of cancers, photocatalysis, and other related fields.