C@CN nanocomposites as quencher for signal-off photoelectrochemical aptasensor with Au nanoparticle decorated perylene tetracarboxylic acid as platform.

Herein, a novel signal-off photoelectrochemical (PEC) aptasensor was proposed for sensitive detection of thrombin on the basis of C@CN nanocomposites as quencher and Au nanoparticles (depAu) decorated perylene tetracarboxylic acid (PTCA) as sensing platform. Owing to the excellent membrane-forming of PTCA and superior conductivity of depAu, the PTCA between two depAu layers can simply and effectively produce an extremely high initial photocurrent to afford a precondition for sensitive biodetection. Thereafter, the assembly of C@CN nanocomposites on electrode via typical sandwich reaction enabled the generation of a significantly decreased photocurrent. Here, the CN with high surface area not only provided massive binding sites for C immobilization, but also partly competed with PTCA in light absorption for producing a significantly smaller photocurrent in the presence of electron donor ascorbic acid (AA). Additionally, both the CN and C have the poor conductivity, which could inhibit the electron transfer to achieve a further decreased photocurrent, effectively improving the sensitivity of proposed biosensor. As a result, the PEC biosensor in a "signal-off" mode showed an extremely low detection limit down to 1.5 fM, providing a sensitive and universal strategy for protein detection.