Ricardo H. Gonçalves

Magnetite Colloidal Nanocrystals: A Facile Pathway To Prepare Mesoporous Hematite Thin Films for Photoelectrochemical Water Splitting

In this study, we demonstrate an alternative and promising way to produce hematite photoanodes with high performance and without the addition of doping or catalytic coating. In this approach, we processed hematite thin films using a colloidal dispersion of magnetite nanocrystals as the precursor. The photoelectrochemical characterization shows that the colloidal approach used to process an undoped hematite photoanode produced a high-performance electrode for water photooxidation with an onset potential as low as 0.8 V(RHE). This value is comparable to the best results reported in the literature for a hematite photoanode modified with catalytic materials. We demonstrate that pure hematite thin films reach 1.1 mA·cm(-2) at 1.23 V(RHE) with back-side illumination.

Synthesis of TiO2 Nanocrystals with a High Affinity for Amine Organic Compounds

This article describes a different approach to the colloidal synthesis of TiO(2) nanocrystals using a polymer melt as a solvent. This approach allowed us to obtain a colloidal dispersion with a high degree of stability in a polymeric solvent, resulting in a transparent colloid. Using this method, it was possible to obtain the TiO(2) nanocrystal with Brønsted acid sites and polymer chains chemically anchored on the nanocrystal surface. The acid surface of those nanocrystals has the chemical property to react in the presence of amine organic compounds and to maintain the colloidal stability. In this way, TiO(2) nanocrystals were combined with a molecular probe containing amine functional groups such as polyaniline. Through the combination of the molecular probe and inorganic nanocrystals, we obtained a hybrid material with interesting chemical, optical, and electronic behavior, making it a promising material for photovoltaic, photochromic, and sensor devices.

Synthesis of colloidal magnetite nanocrystals using high molecular weight solvent

In this work, we describe a single-step synthetic route to obtain magnetic nanocrystals (MN), Fe3O4 nanocrystals, soluble in different solvents. To synthesize grafted MN in a single step, we used a high molecular weight solvent (a polyol) that can be attached to the particle surface, which then transfers its solubility to the particle. Using polyols with different molecular weights and polarity enabled us to control the size, aggregation and morphology. The solubility behavior of the MN confirms our success in transferring the solubility of the adsorbed polymer to the nanocrystal.

Colloidal WO3 Nanowires as a Versatile Route to Prepare a Photoanode for Solar Water Splitting

This work describes a synthetic method to produce a WO(3) nanowire as well as to prepare photoanodes by colloidal nanowire deposition. We also studied the influence of a nanowire phase on the photoanode performance for water splitting. Among the nanowires synthesized by using nonhydrolytic media, the orthorhombic WO(3)·H(2) O nanowire produced a photoanode with excellent performance (a photocurrent of 1.96 mA cm(-2) at 1.23 V(RHE) ) and good photocurrent stability during long-term analysis (chronoamperometry test). The structural and photoelectrochemical characterization showed the importance of nanostructural features such as exposed (200), (020), and (002) facets and porosity in the WO(3) photoanode performance.

The colloidal nanocrystal deposition process: an advanced method to prepare high performance hematite photoanodes for water splitting

Much research has been devoted to improving the water splitting efficiency of hematite photoanodes. In this study, we demonstrate a significant advance in the colloidal nanocrystal deposition (CND) process to obtain hematite thin films with high photoelectrochemical performance. For this approach, we designed the magnetic field-assisted dip coating process to achieve homogeneous hematite thin films by using magnetic nanocrystals (maghemite) as the precursor. Using this non-aqueous deposition route, we produced undoped and Sn-doped hematite photoanodes with excellent photocurrents of 1.4 mA cm−2 at 1.23 VRHE and 2.7 mA cm−2 at 1.23 VRHE, respectively, using a standard AM1.5 G solar light simulator.

Highly Efficient and Magnetically Recoverable Niobium Nanocatalyst for the Multicomponent Biginelli Reaction

A new magnetically recoverable nanocatalyst was prepared by coating magnetite with niobium oxide (Fe3O4@Nb2O5) by using a simple wet impregnation method. The Fe3O4@Nb2O5 nanocatalyst was fully characterized, and its catalytic activity was evaluated by using the one‐pot, three‐component Biginelli reaction, with the aim to synthesize 1,4‐dihydropyrimidinones, a class of compounds with diverse pharmacological properties. The developed protocol was applied to a wide range of aliphatic and aromatic substrates, and structurally diverse products were obtained in excellent yields. Compared with copper and nickel nanocatalysts, the Fe3O4@Nb2O5 nanocatalyst demonstrated superior catalytic activity at a remarkably low catalyst loading (0.1 mol %). This niobium nanocatalyst could be easily separated from the reaction mixture with an external magnet and was reused several times without any loss of its catalytic activity. Moreover, although the Biginelli reaction is a century‐old reaction, its mechanism is still a controversial subject, and our investigation provided an insight into the reaction mechanism.

Single‐Step Exfoliation and Covalent Functionalization of MoS2 Nanosheets by an Organosulfur Reaction

A simple approach to exfoliate and functionalize MoS2 in a single-step is described, which combines the dispersion of MoS2 in polybutadiene solution and ultrasonication processes. The great advantage of this process is that a colloidal stability of MoS2 in nonpolar solvent is achieved by chemically bonding polybutadiene on the perimeter edge sites of MoS2 sheets. In addition, elastomeric nanocomposite has been prepared with singular mechanical properties using functionalized MoS2 as nanofiller in a polybutadiene matrix with a subsequent vulcanization reaction.

Estudo de polimorfismos genéticos do HLA (classes I e II) e do TNF-á em doentes com sarcoidose

Introduction: Several factors suggest a genetic predisposition to sarcoidosis, namely the recognition of race as a risk factor and the occurrence of familial clustering of cases. Several studies have reported an association of sarcoidosis and HLA class I and especially class II alleles in different populations. Aim: HLA class I, class II and TNF-α genotyping in a group of sarcoidosis patients and its relation with clinical presentation and outcome. Material and methods: A total of 104 sarcoidosis patients were included. Clinical presentation, functional, radiology, BAL findings and organ involvement were studied. HLA– A*, -B*, -C*, DRB1*, DQB1* and TNF-α were genotyped by molecular biology methods. DNA was extracted from peripheral blood and PCR-SSP and PCR-reverse hybridisation methods were used. Allele frequencies were compared with controls from the same region. The X2 test was used for discrete values and the Kruskal-Wallis test for continuous values. Results: When patients were compared with controls we noticed increased frequencies of B*08 (10.6% vs. 6.1%), O.R. = 1.8, C.I. = [1.1;3.1], p = 0.02; DRB1*12 (4.3% vs. 1.7%), O.R. = 2.63, C.I. = [1.1;6.1], p = 0.03. Patients with erythema nodosum have increased frequencies of the alleles DRB1*03 (28% vs. 9.3%), R.R. = 2.39, C.I. = [1.5;3.8], pc = 0.01 and DQB1*02 (38% vs. 18%), R.R. = 2.1, C.I. = [1.3;3.3], pc = 0.02. Allele DQB1*03 is decreased in patients with obstructive pattern R.R. = 0.53, C.I. = [0.3;0.9], pc = 0.05. Allele DRB1*15 is related to restrictive pattern and reduced diffusion capacity (21.1% vs. 6.6%), R.R. = 2.46, C.I. = [1.35;4.48], p = 0.01 and (18.1% vs. 3.8%), R.R. = 1.87, pc = 0.05 respectively. The TNF-α A/A (high) genotype is significantly associated with erythema nodosum (p = 0.04). Conclusions: These data add support to the genetic association of HLA class I and II with sarcoidosis in terms of susceptibility, type of presentation, severity and outcome. Moreover as previously described in other populations, the TNF-α A/A (high) genotype has a significant association with erythema nodosum. Rev Port Pneumol 2008; XIV (6): 727-746

Facile Routes to Produce Hematite Film for Hydrogen Generation from Photoelectro-Chemical Water Splitting

In this chapter, we brief review a recent progress in chemical synthesis used to prepare very promise material to be applied as photoanode in a PEC cell. We discuss the important parameters such as; the interface solid/liquid showing the different challenge that needs to be addressed for obtains higher semiconductor photoanode performance. In addition, we discuss the impact of a variety of morphology applied in a PEC cell to split water and generate hydrogen and oxygen molecular. Finally, we have pointed out the progress of molecular oxygen evolution mechanism from water oxidation under solar light irradiation.