Fig. 2: Structural and surface characterization of the p-GQDs, o-GQDs, r-GQDs, and ro-GQDs.
From: Regulation of functional groups on graphene quantum dots directs selective CO2 to CH4 conversion
a–c TEM images (a), the lateral size distributions (b), and HRTEM images (c) of p-GQDs, o-GQDs, r-GQDs, and ro-GQDs (from top to bottom). Scale bar: 50 nm for Fig. 2a and 2 nm for Fig. 2c. d and e The high-resolution O 1s (d) and C 1s (e) spectra of p-GQDs, o-GQDs, r-GQDs, and ro-GQDs. f The FTIR spectra of p-GQDs, o-GQDs, r-GQDs, and ro-GQDs. The FTIR and XPS spectra together prove the prevalence of –OH groups on both r-GQDs and ro-GQDs. On the contrary, p-GQDs comprise a majority of –C=O groups, and o-GQDs have a predominance of –COOH and –C=O groups. g The Raman spectra of p-GQDs, o-GQDs, r-GQDs, and ro-GQDs, showing that these four GQDs have a similar graphitization degree.
