Síntese e caracterização de dispersões coloidais de óxido de grafeno reduzido e dopado com nitrogênio para aplicação em eletrônica orgânica

Abstract

Graphene is a two-dimensional carbon-composed material with sp2 hybridization that has been extensively studied in the scientific community due to its excellent physical properties and potential technological applications. The oxidation and chemical exfoliation of graphite is generally used to prepare the graphene oxide (GO). In contrast to graphene, the surfaces and edges of the GO are modified with different oxygen groups, such as carboxylates, hydroxyls, carbonyls and epoxy. In this work, GO containing several carbonyl groups was synthesized through modifications of the Hummers method, for this it was used two oxidation processes. Highly stable aqueous dispersions of chemically reduced graphene oxide (rGO) were prepared using different concentrations of hydrazine hydrate as reducing agent. In addition, aqueous dispersions of GO were simultaneously reduced and doped with nitrogen (N-rGO) using chemical reagents and hydrothermal treatments in order to induce n-type doping in this material. Highly uniform thin films of rGO and N-rGO were made on glass substrates and subsequent heat treatments were done to improve their electrical and optical properties. These two materials (rGO and N-rGO), both film and solution, were characterized using different spectroscopic techniques (Raman, UV-VIS, FT-IR, EDS, etc.), and the results showed that GO aqueous solutions with high degree of oxidation and exfoliation were appropriately reduced and doped in order to obtain materials with optoelectronic properties to be applied in prototypes of organic devices. The best N-rGO thin film had a sheet resistance of approximately 8.0x103 Ω / sq with 67% transmittance at 550 nm and sheet concentration of 1.1x1015 (cm2) after thermal treatments performed at low temperatures. These results show that rGO and N-rGO are promising materials for different applications in organic electronics, such as the manufacture of transparent and conductive electrodes.