XF Zhang, S Liu, X Shao – Journal of Luminescence, 2012
The aggregation (inter-layer π−π interaction) and self-rolling up (intra-layer π−π interaction) of chemically derived graphene (CDG) sheets in aqueous dispersion were evidenced by spectral and TEM methods. Their effects on optical properties were studied by UV-vis-NIR absorption spectra, fluorescence emission spectra and fluorescence lifetime measurements under various CDG concentrations. At pH 8.3, CDG sheets formed carbon nanoscrolls by self-rolling up when its concentration is lower than 10 μg/mL. When the concentration is higher than that, CDG sheets aggregated. Upon aggregation, CDG exhibited the decrease of absorptivity, the change of band shape and the deviation from Lambert-Beer law due to inter-layer π−π interaction. The aggregation effect on CDG fluorescence includes the decrease of emission efficiency, the shortening of fluorescence lifetime and the relative increase of the contribution from short-lived emitting species. On the other hand, CDG self-rolling up caused the occurrence of new absorptions (500 and 960 nm) and new emission (after 500 nm), the decrease of fluorescence quantum yield and shortening of fluorescence lifetime. … 3. Experimental. UV–vis-NIR absorption measurements were made with a StellarNet BLACK Comet C-SR diode array miniature spectrophotometer connected to deuterium and halogen lamp by Optical fiber in 10 mm quartz cuvettes.
![Fig. 1. The dependence of UV-vis-NIR absorption spectra of CDG on its concentration (a), the plot of absorbance against [CDG] (b) and the plot of absorptivity upon CDG concentration (c). Solvent: water, pH 8.3.](https://www.stellarnet.us/wp-content/uploads/Fig-1-Fluorescence-of-Chemically-Derived-Graphene-Effect-of-Self-Rolling-up-and-Aggregation.jpg)
Fig. 1. The dependence of UV-vis-NIR absorption spectra of CDG on its concentration (a), the plot of absorbance against [CDG] (b) and the plot of absorptivity upon CDG concentration (c). Solvent: water, pH 8.3.
Fig. 2. top: TEM image of a nanoscroll formed by CDG under low concentration (4 μg/mL). Bottom: TEM image of CDG sheets under high concentration (20 μg/mL).
