The optical properties of top-down synthesized oxidized graphene quantum dots (ox-GQDs) and nitrogen-incorporating graphene quantum dots (N-GQDs) along a range of hydrothermal treatment temperatures were observed. By controlling the hydrothermal treatment temperature, different chemical states of nitrogen atoms were incorporated into GQDs. Below 150 °C, edge-terminating amines and amides dominated the nitrogen content of N-GQDs. Above 150 °C, nitrogen was primarily present in the forms of pyridinic, pyrrolic and quaternary N. In addition to the absorbance and emission profiles of ox-GQDs and N-GQDs, pH-dependent emission spectra were collected to probe chemical states of nitrogen atoms and investigate the relationship between nitrogen location and photoluminescence.
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This work was supported by the National Science Foundation under Cooperative Agreement No. 1355438. The purchase of a new XPS system recently installed at the University of Kentucky was supported by the fund from the NSF EPSCoR grant (grant no. 0814194).
Electronic supplementary information (ESI) available. See DOI: 10.1039/c7ra09252k
Pillar-Little, Timothy and Kim, Doo Young, "Differentiating the Impact of Nitrogen Chemical States on Optical Properties of Nitrogen-Doped Graphene Quantum Dots" (2017). Chemistry Faculty Publications. 91.