An activated RDX-Fe2O3 xerogel in a Si-microchannel plate (MCP) has been successfully prepared by a novel propylene epoxide-mediated sol-gel method. A decrease of nearly 40 °C in decomposition temperature has been observed compared with... more
An activated RDX-Fe2O3 xerogel in a Si-microchannel plate (MCP) has been successfully prepared by a novel propylene epoxide-mediated sol-gel method. A decrease of nearly 40 °C in decomposition temperature has been observed compared with the original cyclotrimethylene trinitramine (RDX). The RDX-Fe2O3 xerogel can release gas and solid matter simultaneously, and the ratio of gas to solid can be tailored easily by changing the initial proportions of RDX and FeCl3·6H2O, which significantly enhances the explosive and propulsion effects and is of great benefit to the applications. The approach, which is simple, safe, and fully compatible with MEMS technology, opens a new route to the introduction of organic energetic materials to a silicon substrate.
The synthesis of a light-sensitive polyurethanebased composite material (PUX-NO) is described. In its polyurethane medium, PUX-NO contains entrapped silica xerogel particles in which a photoactive manganese nitrosyl has been incorporated.... more
The synthesis of a light-sensitive polyurethanebased composite material (PUX-NO) is described. In its polyurethane medium, PUX-NO contains entrapped silica xerogel particles in which a photoactive manganese nitrosyl has been incorporated. Green flexible films of PUX-NO readily release nitric oxide (NO) only when exposed to low power (mW) visible light. Incorporation of the nitrosyl in the xerogel not only retains the nitrosyl (NO donor) within the composite material but also provides the right extent of hydration. Pre-swelled films of PUX-NO have water content close to 30 Wt % and such films can be stored for months under slightly moist condition without loss in NOdelivering capacity. The NO-releasing parameters of the film have been determined. The NO-releasing capacity of PUX-NO films can be conveniently altered by changing the amount of the nitrosyl as well as the thickness of the films. Patches of PUX-NO film have been successfully employed to reduce drastically bacterial loads of both gram-positive and gram-negative bacteria including methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii under the total control of light. Effective control of infections by these bacterial pathogens via delivery of proper doses of NO only to the sites of infection appears feasible with PUX-NO films. V
A fuel cell is an electrochemical device that converts the chemical energy of a fuel (e.g. hydrogen, methanol) directly into electrical energy following the principle is shown in Figure 1. The main advantages of fuel cells are: (i) they... more
A fuel cell is an electrochemical device that converts the chemical energy of a fuel (e.g. hydrogen, methanol) directly into electrical energy following the principle is shown in Figure 1. The main advantages of fuel cells are: (i) they produce zero or very low emissions, especially greenhouse gases, (ii) they produce electrical energy with a very high yield (up to 60%), (iii) they can be used for combined heat and power purposes, further increasing the efficiency of energy production and (iv) they are entirely silent.
In this paper, TiO₂ prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and... more
In this paper, TiO₂ prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO₂ nanoparticles of 6-8 nm are formed, with a specific surface area between 200 and 275 m²·g. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO₂ nanoparticles of 6-8 nm with a specific surface area between 185 and 240 m²·g are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO₂ materials through Ti-O-N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with -nitrophenol show a marked improvement for all doped catalysts under visibl...
Carbons from cane molasses with 8 m2 g−1 BET area yielded capacitances up to 153 F g−1 at 0.5 mV s−1 in 1 M H2SO4, with 35.2% pseudocapacitance contribution, due to the high surface concentration of quinone and carbonyl groups.
Carbons from cane molasses with 8 m2 g−1 BET area yielded capacitances up to 153 F g−1 at 0.5 mV s−1 in 1 M H2SO4, with 35.2% pseudocapacitance contribution, due to the high surface concentration of quinone and carbonyl groups.
Hydrophobic films are characterized to repel water or aqueous solutions when in interaction with coated surfaces or any materials with hydrophobic properties. These materials have attracted attention due the technological properties,... more
Hydrophobic films are characterized to repel water or aqueous solutions when in interaction with coated surfaces or any materials with hydrophobic properties. These materials have attracted attention due the technological properties, like: self-cleaning, anti-icing, antiadherent and anti-corrosion. This study aimed to obtain the hydrophobic film at room temperature using the vinyltriethoxysilane (VTES) on stainless steel AISI 204 in sol-gel solution by dip-coating process, with the purpose to increase the corrosion resistance of metal substrate. The hydrolysis reaction was prepared a solution with a percentage ratio of silane/ethanol/water 4/48/48% in volume. Some parameters of the solution and the substrate surface were varied, such as silane hydrolysis time in the sol solution at 2 and 24 hours, and the roughness of the substrate by blasting process with microparticles of aluminum oxide and it was compared with the smooth substrate (unchanged). The film was characterized by scanni...
Carbons from cane molasses with 8 m2 g−1 BET area yielded capacitances up to 153 F g−1 at 0.5 mV s−1 in 1 M H2SO4, with 35.2% pseudocapacitance contribution, due to the high surface concentration of quinone and carbonyl groups.
Resumo Filmes de TiO2 dopados com Nb podem associar propriedades como TCO (transparent conductive oxide) e super-hidrofilicidade, quando ativados por luz UV. Filmes metálicos de Ti-Nb foram depositados sobre substrato de vidro via triodo... more
Resumo Filmes de TiO2 dopados com Nb podem associar propriedades como TCO (transparent conductive oxide) e super-hidrofilicidade, quando ativados por luz UV. Filmes metálicos de Ti-Nb foram depositados sobre substrato de vidro via triodo magnétron sputtering e posteriormente os filmes foram oxidados em atmosfera ambiente a 600 °C durante 1,0 h em condições similares àquelas usadas no tratamento térmico de vidros. Medidas de rugosidade, cristalização, composição química e molhabilidade foram realizadas através das técnicas de microscopia de força atômica, difração de raios X, fluorescência de raios X e ângulo de contato, respectivamente. Os resultados mostraram que os filmes foram completamente oxidados, tornando-se visualmente transparentes à luz visível com cristalização da fase rutilo-TiO2. Após irradiação com luz UV, os filmes TiO2:Nb apresentaram rugosidade em escala nanométrica podendo ser classificados como super-hidrofílicos, com valores de ângulo de contato similares àqueles...
Organic–inorganic xerogel networks were synthesized from bacterial poly (3-hydroxybutyrate) (PHB) for potential biomedical applications. Since silane-based networks usually demonstrate increased biocompatibility and mechanical properties,... more
Organic–inorganic xerogel networks were synthesized from bacterial poly (3-hydroxybutyrate) (PHB) for potential biomedical applications. Since silane-based networks usually demonstrate increased biocompatibility and mechanical properties, siloxane groups have been added onto polyurethane (PU) architectures. In this work, a diol oligomer (oligoPHB-diol) was first prepared from bacterial poly(3-hydroxybutyrate) (PHB) with an environmentally friendly method. Then, hexamethylene diisocyanate or biobased dimeryl diisocyanate was used as diisocyanate to react with the short oligoPHB-diol for the synthesis of different NCO-terminated PU systems in a bulk process and without catalyst. Various PU systems containing increasing NCO/OH molar ratios were prepared. Siloxane precursors were then obtained after reaction of the NCO-terminated PUs with (3-aminopropyl)triethoxysilane, resulting in silane-terminated polymers. These structures were confirmed by different analytical techniques. Finally, ...
This work studied ultrathin films of titanium oxide deposited by the technique r. f. reactive sputtering with different oxygen flows and different deposition times. Optical properties were studied (ultra-violeta/Visível) and the surface... more
This work studied ultrathin films of titanium oxide deposited by the technique r. f. reactive sputtering with different oxygen flows and different deposition times. Optical properties were studied (ultra-violeta/Visível) and the surface morphology (Atomic Force Microscopy). The composition and structural properties of the films were analyzed by X-ray diffraction and Rutherford Backscattering Spectroscopy. The films are amorphous and rough (fractal dimension around 2.6 to 2.7 and roughness around 1.6 to 2.5 nm). The stoichiometry was fairly close to the titanium dioxide (TiO2). The optical energy Gap obtained by three different models presented values between 3.0 to 3.5 eV.
Este trabalho foi dedicado ao desenvolvimento de filmes finos de ácido hialurônico e quitosana para a captura de células tumorais prostáticas. Os recobrimentos foram feitos com a técnica Layer-by-Layer, por meio da qual são construídas... more
Este trabalho foi dedicado ao desenvolvimento de filmes finos de ácido hialurônico e quitosana para a captura de células tumorais prostáticas. Os recobrimentos foram feitos com a técnica Layer-by-Layer, por meio da qual são construídas camadas alternadas de polieletrólitos de cargas opostas. Devido à interação dos receptores CD44, superexpressos em células tumorais, com o ácido hialurônico, este configurou a última camada depositada nos filmes. Foram utilizadas condições variadas de pH e número de bicamadas, de forma a investigar tais fatores nas propriedades físico-químicas e no potencial seletivo dos recobrimentos. As caracterizações foram feitas através das técnicas de Perfilometria, Ângulo de Contato,UV-Visível e Microscopia de Força Atômica. Já os testes de adesão foram realizados com células tumorais prostáticas da linhagem PC3.
In this paper, TiO₂ prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and... more
In this paper, TiO₂ prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO₂ nanoparticles of 6-8 nm are formed, with a specific surface area between 200 and 275 m²·g. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO₂ nanoparticles of 6-8 nm with a specific surface area between 185 and 240 m²·g are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO₂ materials through Ti-O-N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with -nitrophenol show a marked improvement for all doped catalysts under visibl...
The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to... more
The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to control the layer nano/microstructure. Here, we detail the production of mesoporous CuGaS₂ (CGS) and ZnS layers from spin-coating and subsequent cross-linking through chalcogen-chalcogen bonds of properly functionalized nanocrystals (NCs). We further produce NC-based porous CGS/ZnS bilayers and NC-based CGS-ZnS composite layers using the same strategy. Photoelectrochemical measurements are used to demonstrate the efficacy of porous layers, and particularly the CGS/ZnS bilayers, for improved current densities and photoresponses relative to denser films deposited from as-produced NCs.
RESUMO Tem sido creditado à nanociência um destacado papel de prover pleno entendimento sobre o comportamento macroscópico dos materiais, por ser esse campo da ciência capaz de realizar estudos e perceber, com distinção, propriedades ou... more
RESUMO Tem sido creditado à nanociência um destacado papel de prover pleno entendimento sobre o comportamento macroscópico dos materiais, por ser esse campo da ciência capaz de realizar estudos e perceber, com distinção, propriedades ou fenômenos físicos e químicos da matéria em escala nanométrica. A exploração do conhecimento da matéria em níveis tão ampliados demanda a utilização de técnicas aprimoradas de análise, surgidas principalmente nos últimos anos. Para o ramo dos materiais cimentícios, a Microscopia de Força Atômica (MFA) é tida em parte da literatura como a principal técnica voltada às análises e estudos no campo da nanociência. Contudo, para que funcione bem, a técnica demanda amostras altamente planas, o que se constitui um problema quando se trata de amostras de materiais cimentícios, de tendência naturalmente irregular e rugosa. Além disso, a técnica não realiza análise química da região varrida. Estas dificuldades são tratadas neste trabalho, que, como meta, procura...
The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to... more
The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to control the layer nano/microstructure. Here, we detail the production of mesoporous CuGaS₂ (CGS) and ZnS layers from spin-coating and subsequent cross-linking through chalcogen-chalcogen bonds of properly functionalized nanocrystals (NCs). We further produce NC-based porous CGS/ZnS bilayers and NC-based CGS-ZnS composite layers using the same strategy. Photoelectrochemical measurements are used to demonstrate the efficacy of porous layers, and particularly the CGS/ZnS bilayers, for improved current densities and photoresponses relative to denser films deposited from as-produced NCs.
A deposição de recobrimentos em uma superfície visa a melhoria de determinadas propriedades do material tais como as propriedades químicas e tribológicas. O desgaste pode ser minimizado seja pelo aumento da dureza da superfície seja pela... more
A deposição de recobrimentos em uma superfície visa a melhoria de determinadas propriedades do material tais como as propriedades químicas e tribológicas. O desgaste pode ser minimizado seja pelo aumento da dureza da superfície seja pela diminuição da adesão entre as superfícies. Atualmente, ferramentas de corte são recobertas com TiN, TiCN e (TiAl)N, através de processos de deposição física a vapor, com o objetivo de aumentar a sua vida útil. Estes recobrimentos são caracterizados por uma alta dureza, excelente aderência, baixa porosidade, alta estabilidade química e térmica, entre outras características. As ferramentas de corte estão sujeitas a processos de degradação também por oxidação e corrosão. Nestes processos, a rugosidade da superfície tem um papel fundamental. O trabalho em questão objetiva o desenvolvimento de uma metodologia para aplicação de análise topográfica tridimensional (3D) ao estudo de processos de oxidação de recobrimentos e de superfícies. Neste estudo, reali...
The use of gold as a promotor of alkane hydrocarboxylation is reported for the first time. Cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid (up to 55% yield) with CO, water, and peroxodisulfate in a water/acetonitrile medium... more
The use of gold as a promotor of alkane hydrocarboxylation is reported for the first time. Cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid (up to 55% yield) with CO, water, and peroxodisulfate in a water/acetonitrile medium at circa 50 °C has been achieved in the presence of gold nanoparticles deposited by a colloidal method on a carbon xerogel in its original form (CX), after oxidation with HNO₃ (-ox), or after oxidation with HNO₃ and subsequent treatment with NaOH (-ox-Na). Au/CX-ox-Na behaves as re-usable catalyst maintaining its initial activity and selectivity for at least seven consecutive cycles. Green metric values of atom economy or carbon efficiency also attest to the improvement brought by this novel catalytic system to the hydrocarboxylation of cyclohexane.
Wound healing treatments continue to be a medical challenge, since complications usually lead to chronicization and comorbidities. Natural inorganic ingredients such as clays have been demonstrated to exert useful activities in this... more
Wound healing treatments continue to be a medical challenge, since complications usually lead to chronicization and comorbidities. Natural inorganic ingredients such as clays have been demonstrated to exert useful activities in this regard. Hectorite is a smectite clay with desirable rheology due to its layered structure and remarkable swelling capacity. These properties make it an appropriate excipient for semisolid systems. Nonetheless, the biocompatibility of natural hectorite has been scarcely addressed; the majority of studies centered on synthetic or functionalized hectorites. The aim of this study was to prepare and characterize a hectorite/spring water hydrogel. The hectorite clay mineral was subjected to a solid-state characterization, while the hydrogel (HTgel@10) was evaluated in terms of rheology, pH and in vitro biocompatibility and wound healing. Results demonstrated that the hectorite possessed a remarkable purity (84% w/w of hectorite), very similar to that of simila...
