Fig. 8

Optical absorption and fluorescence properties of GO. a UV-vis absorption spectra of GO dispersion and reduced GO (rGO) [26]. b Fourier transform infrared (FTIR) spectra of GO with different sizes. GO1, GO2, GO3, GO4, and GO5 have average size of 390, 200, 140, 60, and 38 nm [74]. c Photoluminescence (PL) spectra of GO dispersion with a different pH value [75]. d Fluorescence of GO as a function of laser power. e The PL intensity as a function of angle β between the plane of GO flake and polarization of excitation light [76]