Medidas de concentração de grafeno em solução através de extinção de fluorescência

Abstract

One of the main routes for producing large-scale graphene is the liquid phase exfoliation (LPE) method. In this type of system, graphene concentration is one of the most important factors in the characterization aspect. So far, the most accurate way to perform this type of measurement is gravimetry. However, spectroscopic techniques can be calibrated to provide alternative (and more versatile) ways of measuring concentration. In the case of graphene in solution, this measurement commonly occurs through the UV-vis absorption technique. Despite being an indirect measurement, and requiring gravimetry calibration, it is a versatile and non-destructive technique, considered to be very useful for measuring the concentration of graphene in solution. In this work, we introduce an alternative optical spectroscopy technique to measure the concentration of graphene in solution. The technique is based on the fluorescence quenching effect. Recent studies have shown an efficient way to visualize graphene sheets deposited on a glass surface using the fluorescence quenching of a certain fluorophore placed in contact with graphene. Our analysis consists of using this extinction effect to measure the concentration of graphene in solution. For that, we prepared solutions of fluorescent molecules with liquid phase exfoliated graphene and monitored the extinction of fluorescence generated by these molecules as a function of graphene concentration. The results show that there is a correlation between the dye fluorescence quantum efficiency and the graphene concentration in the solution, in which the quantum efficiency decreases as the graphene concentration increaes.