▎ 摘　　要

NOVELTY - Electrochemical sensor comprises: a molecularly imprinted polymer film fabricated on an indium tin oxide coated glass substrate, where the molecular imprinted polymer comprises graphene-nickel(IV) sulfide nanocomposite functionally modified with polyaniline and having molecular imprints of indoxyl sulfate. The graphene-nickel(IV) sulfide nanocomposite is prepared by: preparing solutions of nickel nitrate and thiourea in deionized water; adding thiourea solution dropwise in nickel nitrate solution and allowing it to completely mix; adding ethylenediamine drop-wise to solution until the color changes close to violet; keeping the solution under constant stirring overnight at 300 rpm and drying the solution using an infrared lamp for 8 hours to obtain a dried black color powder; grinding the dried black color powder and calcinating at 350° C; and finally, grinding the black color powder to obtain graphene-nickel(IV) sulfide nanocomposite. USE - The sensor is useful as electrode for: detecting indoxyl sulfate in various body fluids comprising urine, serum, blood and plasma (all claimed); and detecting gut microbiota-derived metabolite. ADVANTAGE - The sensor: is capable of quantitative as well as qualitative detection of indoxyl sulfate; has a detection limit of 1 μ M to 6 mM; and is connected to an electrochemical analyzer as the readout unit. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: preparing the electrochemical sensor; detecting indoxyl sulfate in a test sample using the sensor; and a device unit for detection of indoxyl sulfate comprising the sensor, and an electrolytic buffer.