CRYSTIAN WILLIAN CAMPOS DA SILVA

CRYSTIAN WILLIAN CAMPOS DA SILVA

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Influence of the solid-state reaction method on copper vanadate samples
2024 - CORREA, DENILSON C.; COSTA, CLEIDILANE S.; PASCA, GABRIEL A.C.; BENTES, BEATRIZ A.; SILVA, CRYSTIAN W.C. da; CARBONARI, ARTUR W.
Copper Vanadate is a material used in various fields [1]. To synthesize this material in a single phase, two samples of CuO were mixed with V2O5 by solid-state reaction. The annealing time was varied for each sample: 12 hours for the first (A1) and 15 hours for the second (A2), both at 700°C. The XRD results show that sample A1 formed Cu2V2O7 (52.1%), Cu2 . 3 2V4O1 1 (27.1%) and Cu3V2O8 (20.8%). Sample A2 formed Cu2V2O7 (41.6%), Cu3V2O8 (30.5%) and Cu2.32V4O11 (27.9%). The estimated crystallite were 104 nm (A1) and 103 nm (A2). The difficulty in obtaining pure samples of copper vanadate can be related to several factors, including the initial composition of the precursors [2] and the solid-state reaction method, which can affect the stoichiometry because it requires heat treatment at high temperatures, which can result in multiple phases [2]. The difficulty in obtaining pure samples of copper vanadate, regardless of the synthesis method used, is widely acknowledged in the literature [3]. It should be emphasized that this study aims to contribute to understanding the processes of synthesis and formation of copper vanadate phases.
Influence of the solid-state reaction method on nickel vanadate samples
2024 - CORREA, DENILSON C.; ANTUNES, MAIARA P.; COSTA, CLEIDILANE S.; PASCA, GABRIEL A.C.; BENTES, BEATRIZ A.; SILVA, CRYSTIAN W.C. da; CARBONARI, ARTUR W.
Nickel vanadate is a material increasingly used in sensors, batteries and other applications. This work aims to obtain and stabilize nickel vanadates using the solid-state reaction method. Three samples were synthed. Sample BI was annealed at 700°C and samples BII and BIII at 800°C, all for 6 hours. The XRD results show that all the samples formed the Ni3V2O8 phase, with an average crystallite of 112 nm for BI and 114 nm for BII and BIII. The SEM data show that sample BI has spherical grains with an average of 0.573 μm, while samples BII and BIII have rectangular grains with an of 3 μm. Given these results, the solid-state reaction synthesis showed promising results for nickel vanadate [1]. It is hoped that this work will contribute to turther research into these materials.
Molybdenum (II) acetate as a precursor for molybdenum trioxide
2024 - SOUZA, KATIUSSE S. de; SILVA, CRYSTIAN W.C. da; BURIMOVA, ANASTASIA; PEREIRA, LUCIANO F.; OTUBO, LARISSA; CARBONARI, ARTUR W.; FREITAS, RAFAEL S. de
Transition metal structures (such as cobalt, nickel, and molybdenium) have been the subject of studies in recent years due to their electrical, catalytic and magnetic properties. Orthorhombic molybdenum trioxide (α-MoO3) is relevant because it is an antioxidant material, leading to its catalytic properties that are influenced by the valence state of molybdenum ions and the local environment where they are inserted. These structures have been investigated in developments of sensors, energy storage and the formulation of gels for the treatment of chronic diseases [1]. In this perspective, the present work proposes the use of the molybdenum (II) acetate as a metallic precursor for obtaining α-MoO3 structures by the thermal decomposition method [2]. The Mo (II) acetate belongs to a group of metal complexes composed of two highly correlated Mo ions, in which each cations are connected to complexes containing oxygen. This reagent could favor, in specific chemical route, the crystallization of MoxOy [2][3]. The syntheses yields were characterized by X-ray diffraction (XDR), scanning electron microscopy (SEM), and energy-dispersive analysis (EDS). The X-ray diffraction results suggested α-MoO3 crystallite of the 77 nm (by the Scherrer equation). By means of microscopy analysis were observed that the obtained morphology is microrod-like, with a of approximately 774 nm and a length of the 37 micrometers. The EDS analysis only showed energies related to molybdenum (Mo) and oxygen (O), confirming the purity of the obtained material.
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, LARISSA
The 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]
The influence of halide ions in the silver nanowires synthesis using polyol method
2024 - SILVA, BARBARA P.G.; SILVA, CRYSTIAN W.C. da; OTUBO, LARISSA
Silver 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.
Synthesis and local characterization of CoO nanoparticles in distinct phases
2024 - SANTOS, SUZILENE V.; COSTA, CLEIDILANE S.; PARAGUASSU, WALDECI; SILVA, CRYSTIAN W.C.; OTUBO, LARISSA; SOUZA, KATIUSSE S.; CORREA, BRUNO S.; MIRANDA-FILHO, ARNALDO A.; FERREIRA, WANDERSON L.; CARBONARI, ARTUR W.; CABRERA-PASCA, GABRIEL A.
The advancement of functional nanomaterials has become a major focus of recent research, driven by the exceptional properties these materials display compared to their macroscopic (bulk) counterparts. Cobalt oxide nanoparticles (CoO-NPs) stand out primarily for their catalytic and magnetic properties, which can enable a range of technological applications, such as advanced catalysts, drug delivery systems, implants, prosthetics, sensors. However, in addition to the dependence on factors such as size, morphology, and functionalization, the properties of CoO-NPs are significantly influenced by the crystal structure. Therefore, local investigation into the polymorphic structures of CoO at the nanometric scale may provide new insights into the local structural and magnetic characteristics of these systems. In this report, we address the synthesis and local characterization of cobalt oxide (CoO) nanoparticles in the rock-salt cubic fcc-CoO and Wurtzite hpc-CoO phases, obtained through thermal decomposition. We analyze the influence of oleylamine and oleic acid ligands on the structural and morphological control of these systems. The obtained nanoparticles were characterized using conventional techniques such as X-ray diffraction (XRD), transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Local characterization was carried out by the perturbed angular correlation (PAC) nuclear technique using the radioactive tracer 111In(111Cd). Measurements were conducted at 295 and 10 K to investigate possible magnetic phase transitions in these systems. XRD results confirmed the formation of fcc-CoO and hcp-CoO phases. The phase fcc was obtained with the pair of oleylamine and oleic acid ligands, while the phase hcp phase was synthesized using only oleylamine. Additionally, nanoparticles synthesized with oleylamine and oleic acid exhibited better morphological control compared to those produced with only oleylamine. Raman spectroscopy analyses suggest a phase transformation process resulting in Co3O4. PAC results for hyperfine interactions at the 111In(111Cd) probe nucleus, indicate that the hcp-CoO phase shows smaller hyperfine magnetic interactions (Bhf = 1 T) compared to the fcc-CoO phase (Bhf = 17 T). This suggests the mechanism of superexchange interactions, which are strongly influenced by the Co-O-Co bond angle, which is 110° for the hpc-CoO phase and 180° for the fcc-CoO phase due to the geometries of the systems.
Simple and fast preparation of transparent conductive films of silver nanowires obtained by a salt assisted polyol method
2024 - SILVA, BARBARA P.G.; SILVA, WILLIAN C. da; SARAIVA, STEFANY R.; OTUBO, LARISSA
Silver 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.