▎ 摘　　要

NOVELTY - Preparing graphene quantum dots with blue fluorescent characteristics involves dispersing residual starch in sweet potato residue in water to form a suspension, transferring suspension into the reaction kettle to hydrolyze the starch to obtain glucose, maltose and aldehydes. The glucose is hydrolyzed under hydrothermal conditions to obtain C=C bonds, and GQDs are obtained under hydrothermal conditions. USE - Method for preparing graphene quantum dots with blue fluorescent characteristics used in the field of heavy metal ion detection in water. ADVANTAGE - The method enables to prepare graphene quantum dots with blue fluorescent characteristics, which has good hydrophilicity, and selectively quench Hg2+ in aqueous solution and applied in the fields of biological imaging, optical sensing and energy storage conversion. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a graphene quantum dot.