Henrique S. Oliveira

Ruthenium complexes endowed with potent anti-Trypanosoma cruzi activity: Synthesis, biological characterization and structure–activity relationships

Although effective against epimastigotes (proliferative form) and of low cytotoxicity in mammals, the aryl-4-oxothiazolylhydrazones (ATZ) display only limited activity against trypomastigotes (bloodstream form) of Trypanosoma cruzi. Considering the metal complexation approach with bioactive ligands as one possible strategy for improving the biological efficacy of ATZ, a set of eight new ruthenium-ATZ complexes (RuCl(2)ATZCOD, COD is 1,5-cyclooctadiene) were prepared, chemically and biologically characterized, including in vitro assays against epimastigotes and trypomastigote forms of the parasite and also assessment of cytotoxicity in mammals. Two of these complexes presented antitrypanosomal activity at non-cytotoxic concentrations on mammalian cells and of higher potency than its metal-free ligands, while the metallic precursor [RuCl(2)COD(MeCN)(2)] showed only moderate antitrypanosomal activity. Comparative analysis between the ruthenium complexes and metal-free ligands demonstrated the usefulness of this approach, with the establishment of new SAR data. Additional pharmacological tests, including a DNA bond assay, gave rise to the proposal of a single preliminary explanation for the molecular origin of the bioactivity.

Nanostructured vanadium-doped iron oxide: catalytic oxidation of methylene blue dye

V-doped iron oxides are used as heterogeneous catalysts to oxidize the dye methylene blue in an aqueous medium containing hydrogen peroxide. XRD and Mossbauer spectroscopy reveal that vanadium is incorporated into the iron oxide structure. The H2O2 pretreatment of the solid catalyst promotes important surface and structural changes in the iron oxides primarily due to the formation of peroxo-vanadium complexes, which specifically enhance the catalytic properties of the material. Transmission electron microscope images show that the H2O2 treatment also tends to decrease the mean particle size of the material grains. V-doped iron oxides were found to play an important role as solid catalysts in H2O2 reactions. The prepared vanadium containing iron oxide was confirmed to exhibit remarkable catalytic activity for the oxidation of methylene blue, an important contaminant from textile industry. In fact, the ESI-MS spectrum obtained for methylene blue after reaction with the V-doped oxide shows hydroxylation by hydroxyl radicals in solution forming species with m/z = 130 and m/z = 110.

Enhanced photocatalytic hydrogen generation from water by Ni(OH)2 loaded on Ni-doped δ-FeOOH nanoparticles obtained by one-step synthesis

Ni(OH)2 loaded on Ni-doped δ-FeOOH photocatalysts were prepared by a simple and low-cost one-step precipitation method. The effect of Ni(OH)2 nanoparticles and Ni2+ doping on the photocatalytic hydrogen production rates by δ-FeOOH in aqueous suspension was investigated. The results showed that the photocatalytic H2-production activity of δ-FeOOH was significantly enhanced by doping with Ni2+ ions and by loading Ni(OH)2 on its surface. The maximum H2-production was obtained for the sample with 20 wt% Ni, which provided 5746 μmol h−1 g−1. This high photocatalytic H2-production is due to the combined effects of Ni2+ doping and Ni(OH)2 loaded on the δ-FeOOH surface. The Ni2+ doping increased the conductivity and charge transfer in δ-FeOOH, whereas the Ni(OH)2 improved the charge separation in the δ-FeOOH and, consequently, the photocatalytic H2-production activity.

A novel floating photocatalyst device based on cloth canvas impregnated with iron oxide

In this paper an innovative and versatile design for a catalytic photoreactor is presented. The photoreactor is based on a floating Polypropylene non-woven fabric canvas (NWF) impregnated with particles of a mixture of iron oxides and oxyhydroxides adhered to the surface of microfibers. The canvas was characterized with different techniques including Mossbauer spectroscopy, Raman scattering, FTIR, and SEM. UV-Vis spectroscopy showed that the impregnated particles presented an average gap of 2.2 eV. The activity and efficiency of the photocatalyst was tested by photodegradation of rhodamine-B (Rh-B) and the results showed that the floating photocatalyst has a high catalytic activity and maintains its efficiency even after five reuse tests at intervals of 90 min with a small average residual concentration of 6.2% Rhodamine-B in each reuse cycle.

Characterization of a Sulfonated Polycarbonate Resistive Humidity Sensor

In this work; resistive moisture sensors were obtained by dip coating sulfonated polycarbonate (SPC) onto silver interdigitated electrodes. Commercial polycarbonate was sulfonated with acetyl sulphate at two different sulfonation degrees corresponding to 9.0 and 18.0 mole %. Impedance spectroscopy was used to investigate the humidity sensing properties at controlled relative humidity (RH%) environments generated from standard saline solutions in the range of 11–90 RH%. For the highest sulfonated sample; in the RH% range investigated (11 to 90%); the sensor impedance changed from 4.7 MΩ to 18 kΩ. Humidity sensors made from sulfonated polycarbonate showed exponential decay behavior of the impedance at constant frequency with the environmental relative humidity. Sample 9SPC presented dielectric relaxation response for environmental humidity between 58 and 90 RH% while sample 18SPC presented dielectric relaxation response for the entire measured range between 11 and 90 RH%. Sulfonated polycarbonate could be a promising material for the fabrication of simple and cheap humidity-sensing sensors for the assessment of relative humidity of the surrounding environment, as suggested by experimental results.

Magnetic Carbon Nanofiber Networks as Support for Ionic Liquid Based Catalyst

In this work, the ionic liquid (IL) 1-hexyl-3-methyl-imidazolium bromide (HMIm.Br) containing Pd suspended nanoparticles was supported on a nanostructured magnetically recoverable carbon nanofiber network. The magnetic material was prepared by a simple reaction of ethanol directly with a nanostructured hematite. SEM, XRD, Mössbauer, Raman, TG/DTA, BET surface area and magnetization analyses suggested that the network is based on carbon nanofibers with carbon coated magnetic Fe nanoparticles. These magnetic networks offer a high exposed carbon fiber area, which has a good interaction with the IL to form a thin layer. Preliminary studies with a Pd dispersed in supported IL as catalyst for the hydrogenation of 1,5-cyclooctadiene showed a membrane effect, which leads to an important increase on the selective hydrogenation of 1,5-cyclooctadiene to cyclooctene.Graphical Abstract

A photocatalytic process for the eradication of dengue through ˙OH generation in the presence of sunlight and iron oxide

Iron oxide was dispersed in a floating matrix based on autoclaved porous brick. Under an incidence of solar radiation ˙OH radicals are generated by the photocatalytic process, completely oxidizing the organic matter. This procedure makes the proliferation of dengue larva unfeasible. Additionally, ˙OH radicals have a remarkable deleterious effect on hatching of A aegypti eggs. The predominant iron phase was hematite (α-Fe2O3), as indicated by the Mossbauer spectroscopy. The formation of ˙OH species was demonstrated by typical m/z values obtained via ESI-MS.

Synthetic Niobium Oxyhydroxide as a Bifunctional Catalyst for Production of Ethers and Allyl Alcohol from Waste Glycerol

A synthetic niobia was modified by treatment with hydrogen peroxide to be used as a catalyst for converting glycerol into petrochemical compounds. The catalytic properties of niobium oxyhydroxide were obtained by generating acidic and oxygenated groups (peroxo groups) on the solid surface. Compounds like ethers and allyl alcohol were obtained. A very active H2O2-modified catalyst showed high activity for the oxidation and dehydration of 91% of glycerol conversion using H2O2 and 46% of allyl alcohol selectivity in volatile phase. The product was analyzed by gas chromatography-mass spectrometry (GC-MS), thermogravimetry-mass spectrometry (TGA-MS) and nuclear magnetic ressonance (NMR). These results strongly suggest that the reactions involve acid and oxidizing species generated after the reaction of niobium with H2O2. H and C multidimensional NMR spectroscopy confirmed the results obtained with GC-MS and showed the production of several compounds after niobia treatment.