▎ 摘　　要

NOVELTY - Preparing composite nano material comprises mixing nano-precious metal-loaded zinc oxide nanorods with N-doped graphene. USE - The method is useful for preparing composite nano material. ADVANTAGE - The nano material has good electrochemical activity, linear range of detection of 1.57-27.53 mu M, and the detection limit is 0.49 mu M. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) composite nanomaterial obtained by the above method; (2) electrochemical sensor, comprises composite nano-material modified glassy carbon electrode; and (3) electrochemical detection method of chrysophanol, comprising crushing the rhubarb containing medicinal materials to obtain medicinal powder, dissolving the medicinal powder in ethanol, extracting by ultrasonic treatment, and detecting the medicinal material extract by electrochemical sensor.