Abstract: Graphene oxide/silver nanocomposite has excellent antimicrobial properties [1]. The traditional methods of incorporation of metal in graphene oxide usually require toxic reagents or with long periods of reaction and in high temperature [2]. The objective of this study is to develop an innovative and sustainable method of incorporating silver into graphene oxide by electron beam. This methodology does not involve toxic reagents or residues and it is carried out in a short reaction time at room temperature. Dispersed graphene oxide was mixed with silver in the complex form in water- isopropanol solution. The mix was submitted to a dose of radiation varying between 150 and 400 KGy. The nanocomposite GO/Ag characterization was performed by thermogravimetry analysis (TGA), X-ray diffraction (XDR), scanning transmission electron microscope coupled to the energy dispersive X-ray spectrometry (TEM/EDS). The antibacterial activity of GO/Ag was observed against Gram negative, Escherichia coli by plate count method. The viable cells of GO and GO-Ag was determined by plating the inoculum after 4h of exposure to different concentrations of the nanomaterials (10, 50, 100, 200 and 500 μg/mL). The results showed that for 500 μg/mL of GO, inactivation cells were ca of 5,4 %, while for GOAg, the concentration to inactivate all cell were 5 times lower (100 μg/mL). The silver nanoparticles size range from 20 to 50 nm. This work showed that GO/Ag nanocomposites that were widely studied by their antibacterial properties can be produce by ionizing radiation. This is a sustainable method that does not require toxic reagents and does not generate hazardous wastes. The short reaction time of some minutes and the ambient temperature also make the process attractive.

JACOVONE, R.M.S.; SOARES, J.J.S.; SOUSA, T.S.; RODRIGUES, D.F.; SILVA, F.R.O.; GARCIA, R.H.L.; VICENTE, E.J.; SAKATA, S.K. Antibacterial activity of graphene oxide/silver nanocomposite synthesized by sustainable process. In: WORKSHOP ON ENVIRONMENTAL NANOTECHNOLOGY, 3rd, October 5-8, 2018, Sorocaba, SP. Abstract... 2018. p. 85-85. Disponível em: http://repositorio.ipen.br/handle/123456789/30124. Acesso em: $DATA.

Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.

Como referenciar este item

Abstract: The storage capacity of electric double layer capacitors or supercapacitors with electrolytes based on deep eutectic solvents (DES) has been investigated in this study. DES composed of L-lactic acid with nicotinamide, L-alanine, ammonium acetate, sodium acetate and choline chloride have all been prepared at a molar ratio of 7:1. Furthermore, urea with choline chloride at a molar ratio of 2:1 has also been used as electrolyte for the electrochemical supercapacitors. The DES supercapacitors were prepared using commercial activated carbon electrodes after removing the volatile organic electrolyte with back-pumping vacuum. The electric characteristics of these supercapacitors with DES electrolytes were determined by cyclic voltammetry at room temperature and above up to 80°C. The cyclic voltammetry scan rates were varied from 2 to 25 mVs-1. The lowest scan rate led to a high specific capacitance of 150±8 Fg-1 for urea with choline chloride at a molar ratio of 2:1 and using a maximum applied potential of 1.7 V. For higher molar ratio (7:1) of Llactic acid with the others hydrogen bond acceptors (HBA) it was necessary to increase the temperature above room temperature to improve the specific capacitance. The best results have been obtained with two solids (urea and choline chloride) as starting compounds for preparing the DES. Equivalent series resistances (ESR) have also been determined in this work employing galvanostatic cycling tests with current densities between 2 and 20 mAg-1.

GALDINO, G.S.; RODRIGUES, W.C.; CRUZ, P.D.; CASINI, J.S.; SAKATA, S.K.; FARIA, R.N. Characteristics of electric double layer capacitors produced with electrolytes based on deep eutectic solvents. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 24., 6-10 de novembro, 2022, Águas de Lindóia, SP. Resumo... 2022. Disponível em: http://repositorio.ipen.br/handle/123456789/33742. Acesso em: $DATA.

Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.

Como referenciar este item

Abstract: In the present work, attempts of reducing a graphene oxide powder using a low temperature hydrogenation disproportionation desorption and recombination process (L-HDDR) has been carried out. A lower processing temperature in large scale production is significant as far as costs are concerned. Graphite oxide was prepared using a modified Hummers’ method and dispersed in ethanol, exfoliated using ultrasonication to produce Graphene Oxide (GO). Investigations have been carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results of L-HDDR processing graphene oxide powder using unmixed hydrogen at 400°C and relatively low pressures (<2 bars) have been reported. X-ray diffraction patterns showed a reduction of graphene oxide with the L-HDDR process. The results showed that the L-HDDR process, as the standard HDDR process, can be applied to the reduction of graphene oxide to produce supercapacitor materials. The advantage of employing the L-HDDR process is a relatively a low temperature would reduce the cost of treatment that is a very important factor for producing large amount of material. Thus, the L-HDDR process has been considered a promising alternative method of reducing graphene oxide with efficiency and possibly in large scale production.

BENITEZ JARA, F.G.; CRUZ, P.V.; BARBOSA, L.P.; CASINI, J.C.S.; PERUZZI, A.J.; SAKATA, S.K.; FARIA, R.N. Low-temperature reduction of graphene oxide using the HDDR process for electrochemical supercapacitor applications. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23., 04-08 de novembro, 2018, Foz do Iguaçu, PR. Resumo... 2018. p. 2922-2922. Disponível em: http://repositorio.ipen.br/handle/123456789/29627. Acesso em: $DATA.

Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.

Como referenciar este item

Abstract: Graphene is nanomaterial with unique physical and chemical properties that makes it a precursor for the synthesis of new materials, such as conductive nanocomposites. Graphene can be obtained by the reduction of graphene oxide, but when it is incomplete, reduced graphene oxide (rGO) is produced with both graphene and graphene oxide properties: it is electrical and thermal conductor, it can be exfoliated in several polar solvents and moreover, the oxygen groups can later be functionalized, affording nanocomposites for electrochemical applications and also in biomaterials. A method of increasing the electrical conductivity of graphene-based compounds is by the incorporation of metallic nanoparticles. When these nanomaterials are joined together the surface area increases for the passage of electric current and the electrical conductivity. The chemical reduction method for the incorporation of metallic nanoparticle on GO involves toxic reagents or it is a time-consuming and it also requires high costs for the removal of excess reagents and by-products. The general synthesis of transition Metal/graphene-based nanocomposites by the electron beam in a sustainable process will be presented. The experiments were performed in a 1.5 MeV electron accelerator at room temperature and no hazardous wastes were generated. The nanocomposites were characterized by FT-IR, DRX and TEM/EDS as metallic nanoparticle at the average size of 5-20 nm incorporated into reduced graphene oxide layers. The electrochemical behavior of these nanocomposites was evaluated by cyclic voltammetry.

SAKATA, S.K.; SOBRINHO, L.F.; JACOVONE, R.M.S.; SOARES, J.J.S.; TOMINAGA, F.K.; ANGNES, L.; GARCIA, R.H.L. Sustainable synthesis of transition metals/graphene oxide nanocomposites by electron beam irradiation. In: PAN AMERICAN CONGRESS OF NANOTECHNOLOGY, 1st, 27-30 de novembro, 2017, Guarujá, SP. Abstract... 2017. Disponível em: http://repositorio.ipen.br/handle/123456789/29052. Acesso em: $DATA.

Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.

Como referenciar este item

Abstract: Graphene oxide (GO) is a unique material that can be described as a single monomolecular layer of graphite containing various oxygen functionalities such as epoxide, carbonyl, carboxyl and hydroxyl groups. Chemical modifications at the surface of the graphene oxide through the incorporation of magnetite can provide magnetic properties to these nanomaterials. This work aims to synthesize and characterize graphene oxide/magnetite (GO/M) nanocomposites, evaluating the different proportions of incorporated magnetite. The synthesis of graphene oxide/magnetite nanocomposites was performed by co-precipitation of iron salts on the graphene oxide (GO) particles in alkaline medium. The characterization of the nanocomposites was performed by thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), X-ray diffraction (XRD), nanoparticle tracking analysis (NTA) and scanning electron microscopy (SEM). The thermogravimetric results showed the incorporation of approximately 20, 50, 70 and 80% of magnetite to the graphene oxide. Regarding the hydrodynamic size, for the magnetite, mode values of 31.3 ± 1.3 nm were determined, whereas for the GO/M, the mode values of size ranged from 72.8 to 194 nm. The results of XRD and FTIR showed the respective characteristic diffraction and absorption peaks only for graphene oxide, magnetite and GO/M(20%). It was not observed characteristic peaks for the other samples of graphene oxide that have higher loads of magnetite incorporated.

TOMINAGA, F.K.; SAKATA, S.K.; SOARES, J.J.S.; JACOVONE, R.M.S. Synthesis and characterization of magnetic graphene oxide nanocomposites. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23., 04-08 de novembro, 2018, Foz do Iguaçu, PR. Resumo... 2018. p. 4680-4680. Disponível em: http://repositorio.ipen.br/handle/123456789/29553. Acesso em: $DATA.

Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.

Como referenciar este item

Abstract: This work presents the synthesis of magnetite/reduced graphene oxide nanocomposites (MrGO) via electron beam. The graphene oxide (GO) was prepared according to a modified Hummers’ method and it was characterized using X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Raman spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), zeta potential analysis and cyclic voltammetry (CV) were used in order to investigate the structure and properties of MGO. The data showed GO was reduced using 40 kGy. The CV was performed by applying a MrGO layer on the working electrode of a screen-printed carbon electrode, at a scan rate of 50 mVs-1, potentials range from -0.5 V until 1.0 V in KCl medium (0.05 mol.L-1) adding aliquots of 4 mmol L ?1 ferrocyanide solution. Its results show a similar electrochemical response from both samples (maximum current: 45?A). It can therefore be inferred that magnetite/reduced graphene oxide nanocomposites have a potential for electrocatalysis application.

KAWABATA, V.J.; CARNEIRO, F.W.; JACOVONE, R.M.; ALMEIDA, E.V. de; GARCIA, R.H.; CORIO, P.; SAKATA, S.K. The synthesis of magnetite/reduced graphene oxide nanocomposites by electron beam for eletrocatalysis application. In: PAN-AMERICAN NANOTECHNOLOGY CONFERENCE, 2nd, March 4-7, 2020, Águas de Lindoia, SP. Abstract... 2020. Disponível em: http://repositorio.ipen.br/handle/123456789/31891. Acesso em: $DATA.

Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.

Como referenciar este item