▎ 摘　　要

NOVELTY - Method (M1) for producing a nanocomposite for fabricating an electrochemical biosensor involves (a) preparing carboxylated graphene oxide dispersion, (b) adding the carboxylated graphene oxide dispersion to a mixture of anhydrous ethanol and deionized water under continuous agitation to obtain a carboxylated graphene oxide solution, (c) preparing titanium(IV) hydroxide precursor comprising titanium(IV) oxysulfate-sulfuric acid hydrate powder in deionized water, (d) mixing the titanium hydroxide and the carboxylated graphene oxide solution to obtain a homogeneous suspension, (e) drying the homogenized suspension to obtain carboxylated graphene oxide-titanium dioxide, (f) adding hydrazine monohydrate to the carboxylated graphene oxide-titanium dioxide, (g) stirring in an oil bath to obtain carboxylated reduced graphene oxide-titanium dioxide, and (h) filtering and drying the carboxylated reduced graphene oxide-titanium dioxide. USE - The method is useful for producing a nanocomposite for fabricating an electrochemical biosensor, which is useful for detecting food-borne bacteria (all claimed). ADVANTAGE - The method allows fabrication of enzyme-free and label-free biosensor using bacteria-specific aptamer molecule for detection of food-borne bacteria, hence reduces the cost and complexity of fabrication process and ensures simplified fabrication process and increased overall producibility of the biosensor. The electrochemical biosensor is flexible as different species of food-borne bacteria can be detected simply by substituting the bacteria-specific aptamer according to target bacteria, hence the electrochemical biosensor detects a wide range of food-borne bacteria in reliable, rapid and sensitive manner with detection limit of 10 colony-forming units (CFU)/ml. The electrochemical biosensor is portable, hence enables rapid on-site bacteria detection. DETAILED DESCRIPTION - Method (M1) for producing a nanocomposite for fabricating an electrochemical biosensor involves (a) preparing carboxylated graphene oxide dispersion, (b) adding the carboxylated graphene oxide dispersion to a mixture of anhydrous ethanol and deionized water under continuous agitation to obtain a carboxylated graphene oxide solution, (c) preparing titanium(IV) hydroxide precursor comprising titanium(IV) oxysulfate-sulfuric acid hydrate powder in deionized water, (d) mixing the titanium hydroxide and the carboxylated graphene oxide solution to obtain a homogeneous suspension, (e) drying the homogenized suspension to obtain carboxylated graphene oxide-titanium dioxide, (f) adding hydrazine monohydrate to the carboxylated graphene oxide-titanium dioxide, (g) stirring in an oil bath to obtain carboxylated reduced graphene oxide-titanium dioxide, and (h) filtering and drying the carboxylated reduced graphene oxide-titanium dioxide, where the carboxylated reduced graphene oxide-titanium dioxide nanocomposite is deposited on a working electrode of an electrochemical biosensor. INDEPENDENT CLAIMS are included for the following: an electrochemical biosensor comprising working electrode comprising carboxylated reduced graphene oxide-titanium dioxide nanocomposite produced by the above-mentioned method, and a bacteria-specific aptamer molecule bound onto the working electrode as a biorecognition element; and a method (M2) for detecting food-borne bacteria using the electrochemical biosensor involves incubating the biosensor in a diluted food sample, and measuring the bacterial concentration of the food sample.