Dual-mode emission of single-layered graphene quantum dots in confined nanospace: Anti-counterfeiting and sensor applications

摘要

Engineering of the luminescent properties for graphene quantum dots (GQDs) presents two enormous challenges:1) The bandgap of GQDs is mainly determined by structural defects (size,shape,and the fraction of sp2 and sp3 domains),which results in non-stoichiometric nature;2) the preparation methods limit the achievement of an accurate chemical structure of GQDs,leading to many controversial explanations over the relationship between the structural defects and bandgaps.Here,single-layered GQDs with an exact structure are obtained by in-situ reaction of intercalated precursors in the confined nanospace of layered double hydroxides (LDHs).Subsequently,the structure-property relationship is uncovered,demonstrating the enhanced fluorescence and activated room temperature phosphorescence of the as-prepared GQDs-LDHs,which originate from synergistic effects:1) strong confinement provided by the nanospace of LDHs;2) rich O-containing functional groups on the surface of GQDs resulting from LDH catalysis.Moreover,the colorless nature and dual-emission characteristics of GQDs-LDHs satisfy the preconditions as anti-counterfeiting markers for protecting valuable documents (bank notes,commercial invoices,etc.).Particularly,owing to the low toxicity of GQDs and the edible property of LDHs,the GQDs-LDHs/gelatin capsules could be the new generation of potential green anti-counterfeiting material in the field of food and drugs.