Multiple signal-amplification via Ag and TiO2 decorated 3D nitrogen doped graphene hydrogel for fabricating sensitive label-free photoelectrochemical thrombin aptasensor.

In this study, Ag/TiO2/3D nitrogen doped graphene hydrogel (3DNGH) was prepared for the first time and the photocurrent intensity of this material was greatly enhanced, which was attributed to the multiple enhancements accomplished in one step. The porous structure of 3DNGH could provide an exceptionally large accessible surface area, which was beneficial for the anchoring of Ag and TiO2 nanoparticles. The introduction of nitrogen doped graphene and metal nanoparticles was capable to facilitate the charge separation efficiency and accelerate the transfer rate of the photogenerated electron-hole pairs. Then the photoelectrochemical performance was further amplified by the localized surface plasmon resonance of Ag nanoparticles. On the basis of excellent PEC properties of Ag/TiO2/3DNGH, a sensitive label-free PEC sensor has been established for the determination of thrombin successfully. This proposed PEC biosensor exhibited good PEC performances with a wide linear in the range from 0.01p.M. to 10p.M. as well as a relative low detection limit of 3 fM (S/N = 3), indicating that Ag/TiO2/3DNGH would serve as a promising photoactive material in the applications of PEC biosensors.