▎ 摘　　要

Here, a novel method to enhance the electrochemical properties of graphene-modified screen-printed carbon electrode (G/SPCE) with polypyrrole (PPy) nanosheets is proposed. The mechanism of improving the electrochemical sensitivity of G/SPCE was investigated at the molecular level. G/SPCE was modified with PPy nanosheets synthesized by oxidative polymerization to improve its electrochemical properties. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) response of PPy-modified G/SPCE (PPy/G/ SPCE) to K3[Fe(CN)6] (PF) were tested experimentally. The results show that the oxidation current sensitivity of G/SPCE to PF after PPy nanosheets modification increased from 11.12 nA center dot mM-1 to 12.91 nA center dot mM-1 in CV response, and from 8.44 nA center dot mM-1 to 10.72 nA center dot mM-1 in DPV response. The effective reaction area of PPy/G/ SPCE was found to be increased by scanning electron microscopy. And the functional group CAO/C@O in PPy/ G/SPCE, acting as a catalyst for the redox reaction of PF, was also found to be improved by X-ray photoelectron spectroscopy. Furthermore, the adsorption energy, electron transfer and density of states changes of PF molecule on pure and PPy-modified graphene were analyzed based on density functional theory calculation. The calculation results show that the adsorption energy and electron transfer of PPy-modified graphene to PF molecule are significantly increased. The response sensitivity of graphene to PF molecule is greatly enhanced by the synergistic effect generated of PPy and graphene.