▎ 摘　　要

NOVELTY - Rare earth element-labeled graphene oxide nanosheet comprises rare earth element compound connected to graphene oxide nanosheet using amide bond. USE - The nanosheet is useful in biosensing, biological detection, medicine or tumor treatment. ADVANTAGE - The nanosheet utilizes the structural characteristics of graphene oxide, is rich in carboxyl, hydroxyl and epoxy groups, ensures strong ability of complexing rare earth element ions of tetraaza heterocyclic compound, provides convenient and effective method for quantitative analysis of graphene oxide in complex systems, and solves the problem of difficult detection of graphene oxide in biological systems. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for preparing rare earth element-labeled graphene oxide nanosheet, involves (a) modifying carboxyl group to graphene oxide nanosheet to obtain carboxyl modified graphene oxide nanosheet, (b) coupling modified carboxyl group on graphene nanosheet with aminated polyethylene glycol using amide reaction to obtain polyethylene glycol modified graphene oxide nanosheet, (c) coupling nitrogen heterocyclic compound having thiocyanate group with graphene oxide modified with aminated polyethylene glycol using carbon-nitrogen bond to obtain tetrazole heterocyclic compound modified graphene oxide nanosheet, and (d) uniformly mixing graphene oxide nanosheet modified by nitrogen heterocyclic compound with aqueous solution containing rare earth elements to obtain rare earth element labeled graphene oxide nanosheet.