RESUMEN
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 (λ) in the VIS-NIR range (350-1000â nm) except graphene oxide solution and the smallest graphene flakes, and they change linearly with concentration. The optical absorption coefficient (at 660â nm) of pure graphene solution seems to be flake-size dependent, changing from â¼730â mL·mg-1m-1 (for â¼25â µm flake size) to â¼4400â mL·mg-1m-1 (for â¼2â µm 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(λ) 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.
RESUMEN
Insufficient homogeneity is one of the pressing problems in nanocomposites' production as it largely impairs the properties of materials with relatively high filler concentration. Within this work, it is demonstrated how selected mixing techniques (magnetic mixer stirring, calendaring and microfluidization) affect filler distribution in poly(dimethylsiloxane)-graphene based nanocomposites and, consequently, their properties. The differences were assessed via imaging and thermal techniques, i.a. Raman spectroscopy, differential scanning calorimetry and thermogravimetry. As microfluidization proved to provide the best homogenization, it was used to prepare nanocomposites of different filler concentration, whose structural and thermal properties were investigated. The results show that the concentration of graphene significantly affects polymer chain mobility, grain sizes, defect density and cross-linking level. Both factors considered in this work considerably influence thermal stability and other features which are crucial for application in electronics, EMI shielding, thermal interface materials etc.