Cálculo del coeficiente de absorción (α) de nanocapas de grafeno dispersado en disolventes orgánicos

Abstract

In this titration work, the absorption coefficient of graphene nanocaps dispersed in organic solvents was calculated using graphite exfoliation (99% purity) in Liquid Phase (LPE). The suspension was obtained with constant parameters: sonication time, centrifugation and drying. The Initial Concentration (GC, i) at 1 mg / ml in solute-solvent ratio 1: 1. The sonicated samples were centrifuged at a constant angular speed of 1000 rpm for 10 minutes, to obtain the supernatant containing graphene nanolayers. The characterization was performed by the analysis of UV-visible Spectroscopy and Scanning Electron Microscopy (SEM) and Raman spectroscopy. Characteristic wavelengths for graphene suspensions were determined by UV-visible spectroscopy, thus, for Ethanol a wavelength of 275 nm was obtained and for DMF a wavelength of 285 nm corresponding to the transitions π-π * characteristics of the double bond C = C of atoms that make up the graphene layers. The concentrations that were obtained were 20 µg / ml for ethanol and 90 µg / ml for DMF, results that were compared with the scientific literature where the behavior of graphene suspension concentration in sonication, centrifugation times and speeds was studied. Based on this, it was considered to work only for 5 hours, optimal time to obtain stable graphene suspensions and a considerable concentration. The morphological characterization was carried out with the Electronic Scanning Microscopy (SEM), where transparent sheets of dimensions ~ 5 μm were observed. The absorption coefficient was calculated by UV-visible spectroscopy using Lamber-Beer law from the supernatant of graphene suspensions. It is concluded that the calculated absorption coefficients are different from the literature and it is recommended that to calculate it can be done through a calibration curve by diluting the samples.