▎ 摘　　要

A one-step process combining chemical modification and exfoliation for obtaining a graphene (Gs) derivative from pristine graphite is conducted through Friedel-Crafts chemical acylation. This electrophilic substitution reaction results in the carboxylic group (-COOH) of niacin transforming into an acylium ion (-C+=O), which is an active species that replaces the sp(2) C-H of graphite. In addition, highly viscous polyphosphoric acid under mechanical stirring was used to exert strong shear stress on and consequently exfoliate the graphite layers. Raman spectra and absorption spectra demonstrate that the obtained graphene-1-one-pyridine (GsNc) has a highly conjugated structure that facilitates electron transfer in electrochemical processes. This novel GsNc possess high sensitivity toward H2O2 (1157.1 mu A mM(-1) cm(-2)) within a linear concentration range of 1 mu M to 5 mM. The proposed enzyme-free H2O2 sensor exhibits high selectivity and excellent stability. Furthermore, a choline biosensor is developed for detecting H2O2 released in bioreactions. In this biosensor, positively charged GsNc provides optimal conditions for immobilizing choline oxidase (ChOx) through electrostatic interactions. This immobilization retains 83.4% of ChOx bioactivity and is thus excellent for choline determination. This modified electrode has high potential for application in oxidase-based biosensors. (C) 2016 Elsevier B.V. All rights reserved.