Robson Pacheco Pereira

• Professor
• Professor at Military Institute of Engineering

Interactions between riboflavin (of known and reversible electrochemical behavior) and boric acid (electrochemically inactive) were explored to expand the applicability of voltammetric techniques allied to composite sensors aiming at minimum sample consumption. The electrochemical cell used in this research consists of three electrodes: a working e...

Sabe-se que em um dispositivo de conversão e armazenamento de energia, possuir alta densidade de potência e notável durabilidade são características de grande relevância. O supercapacitor (SC) possui essas duas características, porém, ainda é necessário enfrentar desafios durante a fabricação e o gerenciamento do SC. Por isso, o estudo de novos mat...

Abstract In this work, CH3NH3PbI3 perovskite thin films were deposited by the spray-coating method in ambient conditions using different deposition temperatures and annealing times. They were then exposed to high humidity in order to investigate the relation between processing parameters and degradation mechanisms. FTIR and XRD analyses identified...

Methylammonium lead iodide (CH3NH3PbI3) perovskite has been proposed as a key component of thin film solar cells. In this work, the influence of substrate temperature on the properties of spray deposited CH3NH3PbI3 thin films was investigated. The main purpose of this work was to determine the best conditions to deposit and crystallize CH3NH3PbI3 p...

The interest in the development of energy conversion and storage devices using nanostructured materials and nanoparticles based on metal oxides is due to the search to solve the deficiencies present in these devices. Among the possible oxides, molybdenum trioxide (MoO3) has been studied due to its different electrical and optical properties. Its pr...

The present work describes the synthesis and characterization of bismuth oxide (Bi2O3), with interest in the alpha phase, since this oxide has potential for the production of energy conversion and storage devices. As a synthesis method, we used methodologies based on ultrasound perturbation, in addition to the synthesis conventionally described in...

Researchers in the Energy field have shown growing interest in the development of energy conversion and storage devices. However, this type of device still has deficiencies in its systems such as maintaining energy density and preserving power density. In this context, molybdenum oxide (MoOx) nanoparticles are being proposed because they have elect...

Aiming at the use of 3D printing as a tool in the design of electronic components and sensors, the present work has developed a preliminary evaluation of the influence of printing conditions on the electrochemical behavior of PLA and commercial carbon conductor-based composites. For this, characterization experiments were carried out by means of in...

The present work describes the synthesis of iron oxide magnetic nanoparticles (IONP) and citrate-capped IONP (IONP-citrate), via conventional chemical routes and ultrasound-assisted approaches. IONP and IONP-citrate samples were characterized by x-ray diffraction (XRD), vibrational spectroscopy (FTIR), differential scanning calorimetry (DSC), scann...

In the present work, an approach is presented on the use of nanomaterials and devices for the Defense area, aiming to describe, in its more general scope, aspects related to the use of concepts, tools and approaches pertinent to nanotechnology, which influences several other technologies that drive the Defense area. In particular, the development o...

Molybdenum oxide micro- and nanoparticles were synthesized conventionally and under ultrasound perturbation (ultrasound-assisted syntheses). X-ray diffraction (XRD), vibrational infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used to characterize the structure, thermal properties and...

Among the various possibilities of construction of energy conversion and storage devices, nanostructured and nanoparticulate materials based on transition metal oxides have shown optimized properties compared to conventional materials. Molybdenum oxide nanoparticles have been studied in function of their potential for application as electrode mater...

The present work describes the synthesis and characterization of molybdenum trioxide (MoO3), with particular interest in the hexagonal phase and its thermal conversion to the orthorhombic phase, since this oxide has potential for the production of energy conversion devices. Methods based on ultrasound perturbation were employed as synthesis strateg...

In the present work, the interaction between HSA with three potential anti-trypanosomal drugs – (E)-2-benzylidene-hydrazine-carbothioamide (UTS); (E)-2-(3,4-difluoro-benzylidene)-hydrazine-carbothioamide (DFTS) and (E)-2-(2,3,4-trifluoro-benzylidene)-hydrazine-carbothioamide (TFTS) - was studied under physiological conditions by spectroscopic techn...

The interaction between Bovine Serum Albumin (BSA), one of the standard proteins used to study the bioavailability of biological molecules in the bloodstream, and Monensin A (MONA), a commercial drug used in veterinary medicine, was studied by molecular docking and semi-empirical calculations. The computational results suggest that the main scoring...

The determination of the volatile organic solvents dichloromethane (DCM), methyl isobutyl ketone (MIBK), tetrahydrofuran (THF) and toluene (TOL) is applied on toxicological monitoring of employees in various industrial activities. The gas chromatography technique with flame ionization detector and headspace injection system has been applied. The an...

Solid electrolytes based on poly(ethylene oxide)/poly(4-vinyl phenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM) blends and LiClO4 were obtained and characterized by differential scanning calorimetry (DSC), infrared vibrational spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). DSC curves showed a progressive decrease of crystalli...

The optimization of fuel cell materials, particularly polymer membranes, for PEMFC has driven the development of methods and alternatives to achieve systems with more adequate properties to this application. The sulfonation of poly(styrene-co-allyl alcohol) (PSAA), using sulfonating agent:styrene ratios of 2:1, 1:1, 1:2, 1:4, 1:6, 1:8 and 1:10, was...

In the present work, Semi-interpenetrating polymer networks (SIPN) based on polyethyleneimine (PEI) were synthesized and characterized, aiming their future application in fuel cell devices. The membranes were acidified by two methods: (i) absorption of H3PO4 from aqueous solutions and (ii) sulfonation, forming covalently bonded-SO3H. The thermal st...

In the present work, sulfonated (SIPN-SO3H) membranes were obtained from PEI/DGEBA semi-interpenetrating polymer network membranes and characterized by vibrational infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). The membranes exhibited thermal stability higher than 230 degrees C and c...

Semi-interpenetrating polymer network (SIPN) membranes were synthesized from polyethyleneimine (PEI) and DGEBA (diglycidyl ether of bisphenol A) and immersed in H3PO4 solutions in order to obtain proton conductive membranes. The SIPN membranes were characterized by vibrational spectroscopy and thermogravimetric analysis, while the SIPN/H3PO4 system...

A Eletroquímica pode ser brevemente definida como o setor de estudos da Química que se interessa por fenômenos que envolvem transferências eletrônicas por interfaces. Há um crescimento exponencial dos interessados por esta área, fazendo com que a mesma esteja em processo de constante reavaliação e crescimento. As pesquisas em Eletroquímica e Eletro...

In the present work, thermal decomposition kinetics of tetraalkylammonium and 1,4-dimethylpyridinium salts of the complex anion bis(1,3-dithiole-2-thione-4,5-dithiolate) bismuthate ([Bi(dmit)2]−) are addressed. Kinetic parameters for the decomposition reactions were obtained utilizing the Ozawa and Coats–Redfern (CR) models. Entropy, enthalpy, and...

In this study, a series of poly(styrene-co-vinyl phosphonic acid) [P(S-co-VPA)] copolymers were synthesized by the free-radical copolymerization of styrene and vinyl dimethyl phosphonate followed by alkaline hydrolysis. The P(S-co-VPA) copolymers were characterized by size exclusion chromatography (gel permeation chromatography), Fourier transform...

Ternary blends of poly(ethylene oxide) (PEO), poly(bisphenol A-co-epichlorohydrin) (PBE) and poly(vinyl ethyl ether) (PVEE) were obtained as films and characterized by differential scanning calorimetry (DSC) and vibrational spectroscopy (FTIR). From the DSC results, phase diagrams for the ternary blends were determined, where the variation of the v...

In the present work, blends of poly(ethylene oxide) (PEO), poly(acrylonitrile-co-methyl acrylate) (PANMA) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM) were studied by DSC, FTIR and electrochemical impedance spectroscopy (EIS). PEO/PANMA blends were found to be immiscible, while PEO/PVPh-HEM blends are miscible and PVPh-HEM/PANM...

In the present work, the Nafion/Pt interface is simulated utilising molecular model systems in DFT calculations. Results indicate the formation of intermediate structures (represented as R-SO3PtnH and R-SO2PtnOH), which can contribute to the stabilisation of the membrane/catalyst interface in fuel cells. The systems exhibit energy density (E/n) and...

In the present work, proton conductive membranes based on poly(acrylonitrile-co-butadiene-co-styrene) (ABS) were obtained by sulfonation. The sulfonic acid ABS (ABS-SO3H) membranes exhibited thermal stability near 370 oC, similarly to the ABS original polymer. DSC curves of the sulfonic acid membranes showed two glass transition temperatures, assoc...

The MeO2CCH2CH2 ligand in X3SnCH2CH2CO2Me, (X = Cl, Br or I), acts as a C,O-chelating group, via the carbonyl group, both in the solid state and in solutions in non-coordinating solvents. The crystal structures of 1 (X = Cl), a redetermination at 120 K and of I (X = Br), at 298 and 120 K, are reported. Comparison of the intramolecular SnO bond leng...

In the present work, mechanical properties of a stoichiometric hydroxyapatite (HA), synthesized by hydrothermal method, with 1.66 Ca/P molar ratio are investigated as a function of the processing parameters. Cylindrical samples were processed by uniaxial compacting, followed by sintering, aiming to obtain high density HA samples. Density values wer...

The osseointegration of porous titanium implants was evaluated in the present work. Implants were fabricated from ASTM grade 2 titanium by a powder metallurgy method. Part of these implants were submitted to chemical and thermal treatment in order to deposit a biomimetic coating, aiming to evaluate its influence on the osseointegration of the impla...

Synthetic Hydroxyapatite (HA) has been used as coating in order to enhance biocompatibility of titanium implants. Osseointegration at the implant-bone interface can be positively affected by the presence of HA coating and other biocompatible calcium phosphates (CaP) deposited on titanium implants, due to the high biocompatibility of these biocerami...

Sulfonated poly(styrene-co-acrylonitrile) (PSAN–SO3H) membranes were obtained by sulfonation of the original styrene–acrylonitrile copolymer, in different molar ratios, and characterized by vibrational spectroscopy (FTIR), thermal analyses (TGA and DSC) and electrochemical impedance spectroscopy (EIS). The thermal stability of the sulfonated polyme...

The reaction between cis-[Mo(CO)4(piperidine)2] and 2,3,5,6-tetrakis(α-pyridyl)pyrazine (TPP) in the 3:1 (Mo:TPP) stoichiometric ratio afforded the organobimetallic compound {[Mo(CO)4]2(μ-TPP)} (1) in 89% yield. This complex has been characterized by elemental and thermogravimetric analyses, vibrational (FT-IR and FT-Raman) and electronic spectrosc...

Molecular model systems based on propyl phosphonic acid (ppa) were studied by means of density functional theory calculations in order to describe the acid–acid interaction and the formation of the hydration sphere. The formation of ppa dimers is reported and the energetic difference between two dimer structures is presented. The hydration sphere o...

Blends of poly(ethylene oxide) (PEO) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM) were studied by means of synchrotron small and wide angle X-ray scattering (SAXS and WAXS, respectively) and by differential scanning calorimetry (DSC). The DSC measurements were used in the determination of the Flory–Huggins interaction parameter...

The electrosynthesis and characterisation of polypyrrole doped with [Bi(dmit)2]−(Ppy/[Bi(dmit)2]) are reported. It was shown by means of IR spectroscopy that the anion [Bi(dmit)2]− is incorporated into the polymeric matrix. Thermogravimetric analysis showed that Ppy/[Bi(dmit)2] decomposes at 180°C, a higher temperature than [NBu4][Bi(dmit)2] or Ppy...

The MeCOCH2CMe2 ligand in X3SnCMe2CH2COMe (2; X = halide) acts as a C,O-chelating group both in the solid state and in non-coordinating solutions. The intramolecular Sn&bond;O bond lengths in trigonal bipyramidal 2 (X = Cl and I), as determined by X-ray crystallography, indicate that the stronger interaction occurs in 2 X = Cl. Comparisons with the...

The electronic structure, energetics, and vibrational spectrum of poly(ethylene oxide) (PEO) are determined from density functional theoretical calculations on model systems (CH2CH2O)nX2, ((EO)nX2), where X is a termination group, such as methyl or hydroxyl, and n varies from 2 to 8. Geometry optimization was performed on these linear model systems...

A theoretical study of tetrabutylammonium [bis(1,3-dithiole-2-thione-4,5-dithiolato)bismuthate], [NBu4][Bi(dmit)2] is reported. The vibrational spectrum and the molecular orbitals were calculated at the Hartree–Fock level of theory with the pseudo-potential SBKJC for Bi and a basis set of 6-31G or 6-31G(d,p) for the other atoms. The molecular geome...

A polymeric solid electrolyte (PSE) based on a poly(ethylene oxide)/poly(bisphenol A-co-epichlorohydrin) (PEO/PBE) blend with LiClO4 was obtained and characterized by its thermal, morphological, spectroscopic and electrochemical properties. DSC analysis showed suppression of PSE crystallinity for O:M lower than 32. The phase diagram exhibited four...

Blends of poly(ethylene oxide) (PEO) of high molecular weight with poly(bisphenol A-co-epichlorohydrin) (PBE) with high epoxy equivalent were studied spectroscopically, thermally and morphologically. As similar systems of low molecular weight, a single Tg was observed for all blends, indicating miscibility. A progressive decrease in the degree of c...

DSC and optical microscopy were used to determine the miscibility and crystallinity of blends of poly(ethylene oxide) (PEO) with poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM). A single glass transition temperature was observed for all blends, indicating miscibility. A progressive decrease in the degree of crystallinity and in the si...

A new polymeric solid electrolyte based on a PEO/PMVE-MAc blend, complexed with LiClO4, was obtained and characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), polarized light optical microscopy, electrochemical impedance and cyclic voltammetry. DSC traces indicated miscibility for all the PSE samp...

DSC and optical microscopy were used to determine the miscibility and crystallinity of blends of poly(ethylene oxide) (PEO) with poly(methyl vinyl ether–co–maleic acid) (PMVE–MAc). Single Tg was observed for all blends, indicating miscibility. The dependence of Tg on the weight per cent of PEO presents a negative deviation from linearity at high PE...

Ionic complexes, [Q][Bi(dmit)2] (5:QNEt4, NBu4, 1,4-Me2-pyridinium and AsPh4), have been obtained from BiBr3 and [Q]2[Zn(dmit)2] [H2–dmit4,5-dimercapto-1,3-dithiole-2-thione]. As established by the crystal structure determination of [(5:QAsPh4)·1/2DMSO], the cations have near tetrahedral geometries and are well separated from the anions. The ani...