Synthesis and surface photochemistry of graphitized carbon quantum dots

Graphitized carbon quantum dots (CQDs) were synthesized by a simple hydrothermal process with cetyltrimethylammonium bromide (CTAB) as the starting material and nitric acid as surface oxidant. The photoluminescent quantum yield (QY) of CQDs could be greatly enhanced through surface esterification with glycol. Based on the structure characterization, we proposed that the CQDs consisted of the stack of graphene sheets sized several nanometers and their excitation-dependent photoluminescence (PL) should be attributed to the n → π* transition of CO bond of surface carboxylic groups. And the PL of CQDs was obviously enhanced by the esterification of carboxylic groups, possibly due to the increase of the molecular coplanarity or the rigidity.

Graphitized CQD synthesized from carbohydrates through hydrothermal process consisted of the stack of graphene sheets and their excitation-dependent PL should be attributed to the n → π* transition of surface CO bonds. Figure optionsDownload high-quality image (92 K)Download as PowerPoint slideResearch highlights
► Graphitized CQDs were prepared from organic molecule through hydrothermal method.
► Esterification with glycol made the PL of CQDs reached to the QY of ∼10%.
► The excitation-dependent PL may be due to the n → π* transition of surface CO bond.
► Esterification of surface CO bond played a dominant role in the PL jump of CQDs.