A label-free cytochrome c photoelectrochemical aptasensor based on CdS/CuInS2/Au/TiO2 nanotubes

CdS/CuInS2/Au/TiO2 nanotube arrays (NTAs) were fabricated by deposition and dipping technique as well as successive ionic layer adsorption and reaction method, where Au nanoparticles were used to improve the interfacial electron transfer and quantum dots (QDs) of CdS and CuInS2 (4.1 nm) to stimulate the formation of an ideal stepwise band edge structure with TiO2. High and stable photocurrent responses were observed on the NTA electrode. A photoelectrochemical aptasensor toward cytochrome c (cyt c) was then fabricated by immobilization of HS-aptamer on the NTAs via Cd-S bond and Cu-S bond. Sensitive and selective detection of cyt c was achieved with a detection range of 5 pM to 100 nM.