▎ 摘　　要

In this work, we study optical spectroscopy of graphene flakes and its derivatives such as graphene oxide and reduced graphene oxide in the same surfactant-free aqueous solution. We show that transmittance (T) and absorbance (A) spectra of different graphene suspension is nearly feature-less as a function of wavelength (lambda) in the VIS-NIR range (350-1000 nm) except graphene oxide solution and the smallest graphene flakes, and they change linearly with concentration. The optical absorption coefficient (at 660 nm) of pure graphene solution seems to be flake-size dependent, changing from similar to 730 mL.mg(-1)m(-1) (for similar to 25 mu m flake size) to similar to 4400 mL.mg(-1)m(-1) (for similar to 2 mu m flake size), and it is several times higher than in the case of graphene oxide, which also varies with type and level of doping/defects (checked by FTIR and statistical Raman spectroscopy). Finally, we show wavelength-dependent evolution of optical absorption coefficient in the VIS-NIR range, which is roughly mimicking the A(lambda) function but is strongly material-dependent. Our study could be useful for application of graphene solution in optofluidic devices, functional inks or printed flexible optoelectronics. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement