▎ 摘　　要

Improving dispersion of metal nanoparticles on graphene sheet still faces great challenges in fabrication of metalgraphene composite. The study reports one way for synthesis of palladium-graphene composite with histidinefunctionalized graphene quantum dot (His-GQD) as linker and semiconductor. The resulting composite offers a three-dimensional architecture. Small Pd nanoparticles are uniformly dispersed on graphene sheets. The intimate contacts of His-GQD with graphene and Pd nanoparticle create the Schottky heterojunction and leads to an improved catalytic activity. Thermal-switchable sensor based on the Pd-His-GQD-G and poly(N-isopropylacrylamide) (PNIPAM) exhibits better sensitivity, selectivity and long-term stability for electrochemical detection of 4-nitrophenol compared with the reported sensors. The differential pulse voltammetric current linearly increases with the increase of 4-nitrophenol in the range of 0.5-250 mu M with detection limit is 0.10 mu M (S/N = 3). The proposed analytical method has been successfully applied in detection of 4-nitrophenol in water.