▎ 摘　　要

NOVELTY - Fluorescent sensor is claimed. The fluorescent sensor is a reduced graphene oxide-crown ether-fluorescent molecular composite, the crown ether is modified on the surface of the reduced graphene oxide by hydrogen bonding, and the fluorescent molecule is contained within the crown ether. USE - The fluorescence sensor is useful for detecting magnesium ions (claimed). ADVANTAGE - The fluorescence sensor: has moderate binding strength of crown ether to fluorescent molecules, fast and very easy detection, accurate replacement of fluorescent molecules, and excellent specificity and sensitivity. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for producing fluorescence sensor comprising (i) taking graphene oxide to prepare aqueous graphene oxide dispersion solution, adding crown ether, aqueous ammonia and hydrazine, stirring, fully reacting and dialyzing to obtain reduced graphene oxide-crown ether complex solution, and (ii) adding fluorescent molecule into the reduced graphene oxide-crown ether complex solution and carrying out initial reaction to obtain final product.