Preparation of photoactive multilayer films with high photocurrent response and detection of thrombin

Abstract

The CdS quantum dots (QDs) multilayers with high photoelectric conversion efficiency are firstly assembled based on the electrostatic layer-by-layer (LbL) self-assembly between the sequentially adsorbed positively charged Poly(diallyldimethylammonium chloride) (PDDA) and negatively charged CdS quantum dots. The electrodes we fabricated have high photocurrent intensity, which is 8–10 times of the traditional method. Based on CdS QDs multilayers, a sensitive and selective photoelectrochemical (PEC) sensor for thrombin was fabricated by using aptamer (ONS2)-labeled Pt nanoparticles (NPs) as novel energy transfer nanoprobes and thrombin as a ‘protective agent’. In the absence of thrombin, ONS2-labeled Pt NPs could be captured on CdS QDs surface by DNA hybridization between the thrombin aptamer (ONS1) and ONS2 and result in photocurrent quenching of sensing system. After the specific binding of thrombin aptamer and thrombin, however, the Pt NPs could not be captured on CdS QDs surface. The thrombin aptasensor displayed a linear range from 10−10mol/L to 10−15mol/L and a detection limit of 10−16mol/L. Fabrication of QDs multilayers with high photoelectric conversion efficiency is of great significance for the future development of PEC biosensor.