Funcionalização de multicamadas de grafeno com plasmas frios usando diferentes misturas gasosas

Abstract

This work aims to investigate the changes in multilayer graphene (MLG) induced by reactive plasmas of various gaseous mixtures. For this, some analytical methods were used to identify changes in surface morphology (optical microscopy, atomic force microscopy – AFM and scanning electron microscopy - SEM), chemical analysis and crystallographic structure (Raman spectroscopy and X-ray diffraction) and elemental composition (X-ray photoelectron spectroscopy). The main changes observed were in surface morphology. The plasma treatment induced the border corrosion in the MLG flakes, contributing significantly to increase the roughness by more than 5% with CO2 treatment. The elemental composition obtained by XPS showed small incorporation of oxygen (1.55% CO2 treatment) and nitrogen (0.4% N2 treatment), indicating a successful graphene doping. The crystalline structure presented small variation in the dimensions of the unit cells, indicating not significant modification by plasma treatment. An increase the electrical resistivity increased (0.8x10-3 Ω.cm - pristine pellets to 3.1x10-3 Ω.cm - pellet treated with CO2 plasma), caused by defects induction in MLG samples. These treatments create active sites by atom/ion insertion acting as dopants in crystalline structure. Therefore, active sites created by plasma treatment can be explored to develop sensors and biocompatible or bioactives compounds. The use of reactive plasma here proposed can optimize the graphene functionalization at relatively low cost and less time of treatment compared with traditional chemical process currently worldwide used.