▎ 摘　　要

NOVELTY - A gas sensor is prepared by using a graphene oxide-modified indium oxide/gold/manganese oxide composite metal oxide gas sensing material. USE - Gas sensor for detecting flammable gas formaldehyde (claimed). ADVANTAGE - The gas sensor improves the detection sensitivity, and can be prepared in simple and rapid manner. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following: (1) a method for a adding indium salt to the reactor, adding deionized water, stirring at 35 degrees C, introducing ammonia gas, adjusting the pH value of 10, reacting for 3-5 hours to obtain the indium hydroxide colloid, stopping the colloidal solution, and washing colloidal solution with distilled water, adding a concentration of 0.01 to 0.2 mol/L chloroauric acid solution to the precipitate, stirring at room temperature, adjusting the pH value of 10 with ammonia water to form a colloidal solution, dropwise adding a solution of manganese manganocene in tetrahydrofuran to the colloidal solution, adding at 10-20 degrees C, adding sodium borohydride, and stirring for 6-10 hours to obtain a precipitate, centrifuging the precipitate, and washing precipitate with deionized water, placing precipitate in a reaction vessel, placing at 120-140 degrees C for 2-6 hours, and washing and drying to obtain the product, calcining at 200-400 degrees C under inert gas atmosphere for 3-6 hours to obtain the indium oxide/gold/manganese oxide composite metal oxide particles, and grinding and pulverizing the particles, dispersing graphene oxide in deionized water, ultrasonically dispersing to obtain a graphene oxide colloidal solution, and adding the composite metal oxide particles to the graphene oxide colloidal solution, and protecting at 200-400 under inert gas for 3-6 hours to obtain the indium oxide/gold/manganese oxide composite metal oxide particles with surface-attached graphene oxide, drying the surface of the indium oxide/gold/manganese oxide composite metal oxide particles modified by graphene oxide in a mortar for period of time to make the particles uniform, adding a small amount of deionized water and appropriate amount of binder, and fully grinding to form a slurry, applying the resulting slurry to the surface of the substrate, coating at 300-550 degrees C for 2-6 hours, and applying direct current to the aging table, and aging at 5 degrees C for 5-7 days to obtain the finished product (2) a use of gas sensor for detecting flammable gas formaldehyde.