Photoelectrochemical aptasensor based on a ternary CdS/Au/TiO2 nanotube array for ultrasensitive detection of cytochrome c

A novel photoelectrode of ternary CdS/Au/TiO2 nanotube array, fabricated by electrodeposition technique and successive ionic layer adsorption and reaction (SILAR) method, shows strong photon absorption capacity and active charge transfer efficiency. A photoelectrochemical aptasensor was developed to detect cytochrome c (cyt c) by decorating a HS-aptamer on the CdS/Au/TiO2 photoelectrode. Due to the specific binding between the cyt c and aptamer, the cyt c-aptamer complex formed and enhanced the steric hindrances and reduced the e/h + lifetimes, which result in a decrease in the photoelectrical current intensity. Cyt c is, therefore, also quantified based on the decrease in photoelectrical current. The developed aptasensor shows a high specificity and a high sensitivity towards to the cyt c, giving a linear range from 5 pM to 100 nM, and a limit of detection of 3.45 pM.