BARBARA PEREZ GONCALVES SILVA
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Resumo IPEN-doc 30996 Development of flexible magnetic films by the incorporation of Ni/Ni3C nanoparticles in a matrix of Amazonian tannic extract (Myrcia atramentifera)2024 - SILVA, CRYSTIAN W.C. da; SOUZA, KATIUSSE S. de; SILVA, BARBARA P.G.; FREITAS, RAFAEL S. de; LAZAR, DOLORES R.R.; PASCA, GABRIEL A.C.; CARBONARI, ARTUR W.; OTUBO, LARISSAThe development of nanostructured magnetic materials based on Ni and its compounds (Ni/Ni3C) has been the objective of scientific research due to the versatility of applications that these materials. In this context, magnetic films can be applied in a variety of technologies such as data storage, flexible spintronics, chemical detection, and magnetic sensors.[1] Additionally, the growing prospect of obtaining environmentally eco-friendly materials has promoted the use of vegetable matrices for film synthesis, such as tannins, for example. In this work, we report the fabrication of flexible magnetic films on paper substrates by adding Ni/Ni3C nanoparticles to the tannin extract matrix of the Amazonian species Myrcea atramentífera.[2] The tannin extract solution was obtained by processing the species' bark through grinding, sieving, and water extraction for 8 hours at 70°C, followed by filtration and concentration. After this step, a tannin extract suspension containing 0.1% Ni/Ni3C was prepared by dispersion in an ultrasonic processor. The suspension was dispersed onto a paper substrate and dried at 30 °C for 10 minutes. The films were characterized by XRD, SEM, AFM, and TGA/DSC measurements. The structural and morphological results indicate the formation of continuous films with dispersed nanoparticles. Thermal analysis results suggest that the nanoparticles dispersed in the films maintain structural stability up to 350 °C. The films present macroscopic magnetic response at room temperature, which can be attributed to the presence of nanoparticles with a coercive field of 100 Oe and saturation magnetization of 26 emu/g. [3]Resumo IPEN-doc 30994 The influence of halide ions in the silver nanowires synthesis using polyol method2024 - SILVA, BARBARA P.G.; SILVA, CRYSTIAN W.C. da; OTUBO, LARISSASilver nanowires (AgNWs) have been studied due to their great optical and electrical properties, making them potential materials to be applied in transparent conductive films (TCFs). Halide ions, such as chloride (Cl-) and bromide (Br-), have been investigated in the synthesis of AgNWs by many researchers.¹ Cl- are commonly used to control the AgNWs growth by facilitating AgCl formation and controlling Ag+ in the solution thereby inhibiting the growth of silver particles (AgNP). Similarly, Br- are also being investigated as a capping agent due to their ability to adsorb onto the (100) crystal plane of Ag, analogous to the capping agent polyvinylpyrrolidone (PVP). In this study, we investigate the influence of Brand Cl- ions in the synthesis of AgNWs using the polyol method, employing ethylene glycol (EG) as solvent and reducing agent, silver nitrate (AgNO3) as the metallic precursor and PVP as the capping agent. In the absence of halide salts, pyramids and rod structures were observed. When only Cl- is added in the reaction, a mixture of pyramids rods and wires were formed. The addition of Br-resulted in the formation of particles (d=133,7 ± 1,6 nm) attributed to the adsorption of Br- ions on the {100}, {110} and {111} crystal planes of fcc silver. The Uv-vis spectrum of sample with Br- exhibited a band at 430 nm, consistent with literature reports for AgNP. The spectra obtained for samples without halides and sample with Cl- are consistent with larger structures. However, when both halides are introduced in the reaction, longer and thinner AgNWs were produced,as observed through SEM, AFM and UV-vis, stating their important role in the silver nanowires growth. Enhancing our comprehension on the growth process and morphological control is important for optimizing the technological application of AgNWs, especially for TCFs.Artigo IPEN-doc 30768 Simple and fast preparation of transparent conductive films of silver nanowires obtained by a salt assisted polyol method2024 - SILVA, BARBARA P.G.; SILVA, WILLIAN C. da; SARAIVA, STEFANY R.; OTUBO, LARISSASilver nanowires thin films have gained attention due to their excellent optical and electrical properties, being a potential material to be applied in optoelectronic devices as transparent conductive films, deposited on a substrate in a such way that forms a percolated network. We report the synthesis of silver nanowires with average length of 9.5 ± 0.4 μm and diameter of 75 ± 3 nm by a modified polyol method and fabrication of transparent and conductive thin films using a simple and low-cost technique as drop-casting. Additionally, we examined the influence of the drop-casting method in function of number of deposition cycles on the optical and electrical properties of the films through optical absorption and electrical resistance measurements using the two-point methodology. Increasing the number of silver nanowire deposition layers, the optical transmittance decreased from 97 (for one layer) to 60% (for five layers), and electrical resistance decreased from 940 ± 0.35 Ω for the 2-layer film to 32 ± 0.02 Ω, for the 5-layer film. Due to the electrical conductivity range of the produced silver nanowires films, we suggested their application in low-voltage circuits.