Facile one-pot synthesis of visible light-responsive BiPO4/nitrogen doped graphene hydrogel for fabricating label-free photoelectrochemical tetracycline aptasensor

It is fundamental to develop highly efficient visible light-responsive photoelectrochemical (PEC) performance material for fabricating PEC biosensor. Herein, BiPO4/three-dimensional nitrogen doped graphene hydrogel (3DNGH) nanocomposites were prepared for the first time via a facile one-pot hydrothermal route. In this nanoarchitecture, the BiPO4 nanorods were anchored onto the porous structure of 3DNGH. Compared with pristine BiPO4, the absorption of BiPO4/3DNGH has been extend to visible-light region, and the energy band gap of BiPO4/3DNGH was calculated to be 2.10 eV, which was greatly narrower than that of pristine BiPO4 with a band gap of 3.85 eV. Under visible light irradiation, the photocurrent signal of the as-prepared BiPO4/3DNGH was 847.2-fold, 4.1-fold and 2.3-fold enhanced comparing to pristine BiPO4, BiPO4 functionalized reduced graphene oxide and BiPO4/nitrogen doped graphene. The enhancement of such photocurrent signal was attributed to the introduction of 3DNGH, which was capable to improve the charge transfer rate and also the efficiency of visible-light utilization of BiPO4. Based on the excellent PEC properties of BiPO4/3DNGH, a label-free PEC aptasensor for selectivity and sensitivity detection of tetracycline (Tc) was successfully established by using Tc aptamer as a biorecognition element. Under optimized conditions, the proposed PEC aptasensor exhibited a wide linear in the range from 0.1 nmol L−1 to 1 μmol L−1 as well as a low detection limit of 0.033 nmol L−1 (S/N = 3). The prepared BiPO4/3DNGH nanocomposites would serve as a promising visible light-responsive photoactive material for fabrication of PEC biosensors with high performance.