2.3. Characterization of the samples
The reduction of GO sheets and the residual concentration of MB were monitored with a UV–Vis Perkin Elmer lambda 2 Spectrometer in the range 190–900 nm.
3. Results and discussion
In Fig. 1a, we report the UV–Vis spectra of the as prepared GO solution and the GO solution irradiated for 30 min and 90 min, labelled as rGO-30 and rGO-90, respectively.
Fig. 1. (a) UV–Vis KY 02111 of GO (black dashed line) and GO after 30 (blue dotted line) and 90 (green solid spectrum) minutes of laser irradiation; (b) decrease of the GO energy gap upon laser reduction. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)Figure optionsDownload full-size imageDownload as PowerPoint slide
Chemical analyses performed by XPS confirm this view as reported in figure S2 (S.I.). A decrease of the oxygen-containing groups (COH, CO, CO and COOH) and an increase of carbon sp2 (CC) in the basal plane can be noted after the laser irradiation of GO. These results are in accordance with the previously mentioned decrease of the energy gap. In rGO sample the COH and CO peaks are accounted for 17,7% and 24.1%, respectively, instead of 23.4% and 35.9% in the case of the as prepared GO sample. The CC peak in rGO accounted for 44.4% instead of 25.1% in the as-prepared GO, proving the GO reduction.