▎ 摘　　要

NOVELTY - A field-effect sensor preparation method involves preparing uniform conductive graphene film on insulating substrate, plating patterned source and drain electrodes on the graphene film, obtaining field-effect device, plating layer of gold film on surface of the graphene film, annealing in presence of inert gas, obtaining uniformly distributed gold nanoparticles, covalently modifying protoporphyrin by chemical method on the gold nanoparticles which are on surface of the graphene film, obtaining protoporphyrin modified graphene film field-effect device, washing using distilled water and drying using high purity nitrogen. USE - Method for preparing field-effect sensor that is utilized for detecting hydroxyl free radicals. ADVANTAGE - The method enables simply preparing field-effect sensor with suitability for detecting hydroxyl free radicals with high selectivity in a rapid manner. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following: (1) a field-effect sensor prepared by the method (2) a method for detecting hydroxyl free radicals by the field-effect sensor.