▎ 摘　　要

NOVELTY - Graphene biosensor comprises a junction field effect tube (JEFT), a source electrode and a drain electrode of the junction field effect tube connected by a graphene film, where the graphene film is provided with a sample cell, a grid electrode is set on the sample cell, and the graphene film is loaded with nucleic acid aptamer comprising a fully defined sequence of 73 nucleotides (SEQ ID NO: not defined), as given in the specification from 5' end to the 3' end. USE - The biosensor is useful for detecting Escherichia coli (claimed). ADVANTAGE - The biosensor has high Escherichia coli detection sensitivity and specificity with simple and economical operation, and high sensitivity under low voltage and thus ensures good safety. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) preparation method of graphene biosensor; and (2) detecting Escherichia coli.