▎ 摘　　要

NOVELTY - Preparing sandwich-type electrochemical immunosensor involves adding ferrous chloride solution into graphene oxide and then treated using ultrasonic wave in presence of nitrogen at 70-90 degrees C to obtain mixture. The mixture is stirred for 3-5 hours and then aqueous ammonia is added to adjust pH value to 10-11. The mixture is cooled and then washed with water to obtain magnetic graphene oxide solution. The magnetic graphene oxide solution is sonicated and then coupling reagent and dilute hydrochloric acid are added to obtain another mixture. USE - Method for preparing sandwich-type electrochemical immunosensor used for detecting tumor marker (claimed). ADVANTAGE - The method enables to prepare sandwich-type electrochemical immunosensor, that has high sensitivity, accuracy and specificity. DETAILED DESCRIPTION - Preparing sandwich-type electrochemical immunosensor involves adding ferrous chloride solution into graphene oxide and then treated using ultrasonic wave in presence of nitrogen at 70-90 degrees C to obtain mixture. The mixture is stirred for 3-5 hours and then aqueous ammonia is added to adjust pH value to 10-11. The mixture is cooled and then washed with water to obtain magnetic graphene oxide solution. The magnetic graphene oxide solution is sonicated and then coupling reagent and dilute hydrochloric acid are added to obtain another mixture. Sodium hydroxide is added into obtained mixture and then tumor markers primary antibody and bovine serum albumin solution are added to obtain third mixture. The obtained mixture is washed with water to obtain functionalized graphene oxide solution. Melamine is heated at 500-600 degrees C for 3-5 hours under vacuum and then nitride carbon powder and nitric acid solution are added to obtain fourth mixture. The obtained mixture is heated at 120-150 degrees C and then centrifuged to obtain nitride carbon thin film solution. The nitride carbon thin film solution and colloidal gold solution are stirred and then centrifuged to obtain gold nanoparticles carbon nitride film solution. Tumor marker antibodies and bovine serum albumin solution are added into gold nanoparticles carbon nitride film solution and then centrifuged to obtain precipitate. The precipitate is added into water to obtain functionalized carbon nitride solution. The glassy carbon electrode is treated with aluminum powder and then treated with aqueous ethanol and nitric acid solution. The glassy carbon electrode is washed with water. The glassy carbon electrode is immersed in functionalized graphene oxide solution and then kept at 35 degrees C for 1-2 hours. The glassy carbon electrode is immersed in functionalized carbon nitride solution and then kept at 35 degrees C for 1-2 hours and then cleaned to obtain the product.