PAULA TIEMI GOTO
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Resumo IPEN-doc 24851 The study of chemical and physical properties of Polyaniline-Graphene Oxide and Palladium Polyaniline-Graphene Oxide composites2017 - SOBRINHO, LUIZA F.; GOTO, PAULA T.; GARCIA, RAFAEL H.L.; FRANCISCO, DANIEL; ANGNES, LUCIO; SAKATA, SOLANGE K.A Polyaniline (PANI)-Graphene Oxide (GO) composite was studied for the electrical activities. The GO was obtained by modified Hummers method. For the palladium nanoparticles (Pd-NPs) incorporation, it was established an environmentally friendly approach based on electron beam reduction. The chemical characterization was performed by Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetry (TG), X-ray Diffraction (XRD) and for the electrical properties Cyclic Voltammetry (CV) in alkaline medium and conductivity measurements. The FTIR spectroscopy and TG were used to obtain the composition of the synthesized materials, while XRD pattern indicated polymerization quality and the crystallization degree of the samples. The CV and conductivity measurements indicated the electrical activity of the composite. The results showed the GO amount was directly proportional to the resistivity of PANI, and when the Pd (Pd-Pani-GO) was present, the CV showed a larger current than the Pd-GO. The high electrochemical performance of the Pani-GO electrode could be due the increasing active sites for the deposition of polyaniline provided by large surface areas of graphene oxide sheets and the synergistic effect between polyaniline and GO. These results demonstrated the importance and great potential of graphene oxide in the development of high-performance conductivity system based on polyaniline.Resumo IPEN-doc 24836 Gamma radiation assisted reduction of graphene oxide in unoxidized environment2017 - MOURA, TIAGO S.; GOTO, PAULA T.; GARCIA, RAFAEL H.L.; SALVADOR, PABLO A.V.; SANTOS, PAULO S.; SOARES, JAQUELINE J.S.; NODA, LUCIA; SAKATA, SOLANGE K.Graphene is a honeycomb like structure of carbon atoms of sp2 hybridization, with remarkable physical and chemical properties. Perhaps, the most desirable properties of a such material is the quasi-ballistic electronic transport and its excellent thermal conductivity that make graphene an excellent alternative to build electronic devices related to silicon, for instance. However, the lack of organic functions and the strong bonds between carbons in graphene nano-sheets make them unable to undergo functionalization reactions, that is important for many applications such as gas and biochemical sensors or nanoparticles decoration. So, in order to allow the functionalization of graphene nano-sheets and make possible a variety of new applications it was developed a nanomaterial based on the oxidation and exfoliation of graphite: the graphene oxide. This new material has epoxide and hydroxyl groups in the basal planes, with carboxyl groups in the borders, improving the hydrophilic properties and potential for chemical functionalization. Graphene oxide also serves as a starting material to graphene production by reduction routes. Partial reduction of graphene oxide leads to reduced graphene, a nanomaterial that combines both proprieties of graphene and graphene oxide: an excellent electrical and thermal conductivity, high superficial area and remaining oxygen groups that allow its functionalization. In the literature is described different ways to produce reduced oxide graphene from graphene oxide, such as chemical reduction using hydrazine hydrate or NaBH4, thermal reduction using high temperatures and plasma hydrogenation. Here in it is described a sustainable process to reduce graphene oxide in sodium bisulfite solution using gamma radiation. Exfoliated Graphene oxide (1-100mg/L) with NaHSO3 under inert medium was submitted to gamma radiation. The radiation dose ranged from 50 to 500 kGy and the product was centrifuged and analyzed by X-ray diffraction (XRD), Raman and infra-red (FT-IR) spectroscopies. It was observed that depending on the dose total or partial reduction was achieved. This methodology does not produce any toxic residue.