Andrelson W. Rinaldi

AuNp@MOF composite as electrochemical material for determination of bisphenol A and its oxidation behavior study

A composite material based on a metal organic framework (MOF), nanowhisker of Al2O3 silanized with (3-aminopropyl)triethoxysilane (APTES) and gold nanoparticles (AuNp) was synthesized and characterized. This material was used to prepare an electrode based in carbon paste (CPE) and applied as a sensor for the determination of bisphenol A (BPA). The electrochemical characterizations and behaviour of the electrode containing the AuNp@MOF composite exhibited a 2.3 higher electroactive surface area, when compared with just CPE. Using differential pulse voltammetry (DPV), it can be noted that the presence of AuNp plays an important role in enhancing the analyte signal detection of BPA 2.5-fold. A linear increase in emphasizing the response as a function of analyte concentration is demonstrated. In this account, we believe that this composite may be applied in analyticals methods for the determination of BPA and others endocrine disruptors.

Synthesis of zeolite from multilayer food packing and sugar cane bagasse ash for CO2 adsorption

The X/A zeolite crystal mixtures were synthesized using sugar cane bagasse ash (SCBA) as a silicon source and multilayer food packing (MFP) as an aluminum source under hydrothermal conditions at 80 °C for 79–296 hours. The silicon was extracted by alkaline fusion for 40 min at 550 °C with an alkali–SCBA weight ratio of 1:1. The aluminum solution was obtained from MFP using NaOH 1 M (3:1 water–acetone) solution. The synthesized zeolites were analyzed by XRD, FTIR, SEM, and BET. In the XRD results, most of the signals were indexed to zeolite X, and some signals were indexed to zeolite A. The vibration bands in the region 1200–400 cm−1 suggested the presence of the double-six-ring (D6R) zeolite X structure. The crystal morphology is characteristic of the zeolite X, and the specific area found by the BET method was 810.47 m2 g−1. The zeolite with the higher specific area was applied in the CO2 adsorption process until it reached 25 bar by the gravimetric method. The experimentally adsorbed amounts were adjusted with the Langmuir, Freundlich, and Toth models.

Electrochemically induced orientation of copper phthalocyanine thin films

The dependence of the electrochromic and organizational behaviors of copper phthalocyanine (CuPc) evaporated thin films on oxidation level have been investigated. UV-vis experiments with CuPc thin film obtained before cyclic voltammetry display two Q bands in the region between 600 and 700 nm, which correspond to the α form of CuPc. The FTIR spectra show an improved molecular orientation of CuPc molecules, obtained after the electrochemical process. Molecules in the film in the oxidized state (1.27 V) display a plane parallel to the film surface, indicating a flat-on molecular orientation. Spectrum changes observed after one complete voltammetric cycle (between −0.5 and 1.5 V) show an evolution from a mixed molecular organization to an edge-on organization.

Synthesis of α-aminophosphonates using a mesoporous silica catalyst produced from sugarcane bagasse ash

A new green synthesis route is proposed for obtaining a mesoporous material using sugarcane bagasse ash (SCBA) as the silica source. The material obtained was denoted by SBA-16 and its mesostructure was characterized by low-angle X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption techniques. Sulfonic acid groups were introduced to the as-synthesized material, resulting in an acid catalyst denoted by SBA-16/SO3H. The catalytic activities of SBA-16 and SBA-16/SO3H were investigated in Kabachnik–Fields reactions, where α-aminophosphonate compounds were produced. The results show that both products can be considered as promising catalysts, where SBA-16/SO3H showed a slightly better performance than SBA-16.

Bionanocomposites based on mesoporous silica and alginate for enhanced drug delivery

This work reports the preparation, the characterization and the prednisolone release profile of biocompatible hydrogel nanocomposites containing mesoporous silica (SBA) and alginate as a biomaterial for enhanced drug delivery with reduced burst effect and improved mechanical properties. Such systems, which were prepared using specific SBA/alginate-crosslinking chemistry, exhibited interconnecting pore hybrid network owing to both mesoporous silica and hydrogel characteristics. Activated SBA was shown to be a determinant factor in inhibiting initial burst by nearly 90% and the drug was released with minimal burst kinetics. The nanoparticles reduced the movements of polymer chains, affecting macromolecular relaxation, and the distribution of mesoporous silica within the hydrogel made drug release into surrounding liquid less favorable. The proposed systems are biocompatible with human immortalized RWPE-1 prostatic epithelial cells. This report offers an approach of up-to-date interest for the development of advanced biomaterials for further physiological and pathological applications.

Effect of Different Dopants in Films TEOS/MPTS Used to Protect the Carbon Steel

Schiff bases m-toluene N-Salicylideneaniline (m-TOL), (B) m-nitro-N- Salicylideneaniline (m-NTR) and (C) m-methoxy-N-salicylideneaniline (m-MTX) and cerium ions were studied added to 3.5 wt.% NaCl solution and added to the hybrid film based tetraethoxysilane (TEOS) e 3-methacryloxypropyltrimethoxysilane (MPTS). The polarization measurements showed lower current densities for the steel in NaCl with m-MTX, indicating that the m-MTX may be acting as an inhibitor. The hybrid films were doped with the m-MTX, Ce (III) or Ce (IV). Electrochemical measurements of open circuit potential (EOC), polarization curves and electrochemical impedance spectroscopy (EIS), were used to evaluate the corrosion behavior of the hybrid films. According Electrochemical Impedance measurements, all hybrid films, provided protection to the carbon steel. The films doped with Ce (IV), provided greater protection than the other, which indicates that this is the most suitable dopant for use in films.

Synthesis and characterization of the polyaniline dopant Schiff base

The Schiff base, N-salicilidenoanilina was used as dopant to induce polymerization of aniline and thus preparing polyaniline (PAni). The different conditions of preparation, including Schiff base structure, and the dosage of acidity reaction medium, were investigated to discuss the influence of these conditions relative conductivity of the resulting samples. The products were also characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis), electrochemical impedance spectroscopy (EIE). The results showed the synthesis conditions play an important in the formation and the final properties of the polyaniline

Synthesis of some derivatives of compounds β-aminoketonic through Mannich reaction by usingbiocatalysts

The Mannich reaction is one of the most widely used reactions in organic chemistry, and also one of the first examples of a multicomponent reaction already described on the literature. This reaction results in β-aminocarbonylated compounds which allow the generation of several structures that can be used in the synthesis of both biologically active molecules, and natural products, however, just a few synthetic routes resulting in the formation of β-aminocarbonylated compound are known. In this sense, new methodologies have been developed by involving new catalysts or chiral auxiliaries in the synthesis of β-aminocarbonylated compounds with biological activity. One of these methodologies is the biocatalysis, which is a technique that uses biological catalysts, like enzymes or micro-organisms to convert a substrate in a limited number of enzymatic steps. The use of micro-organisms, plants or isolated enzymes as chiral catalysts has proportioned a significant advance in the synthetic chemistry, because it is known that the biocatalysts have selective catalytic sites that afford the formation of enantiomerically pure products and which is extremely important, because it is known that differences of the chirality may have tragic or spectacular effects in humans. Concerning to the environmental issue, the biocatalysis is placed within the context of a new philosophy called Green Chemistry. However, in the State of Mato Grosso do Sul the researches involving this issue of biocatalysis are still incipient once that by the year of 2010 there was only one research group focused on this theme registered in the Lattes Platform in the State. Because of the need of support to the researches focused on this issue in the State of Mato Grosso do Sul and to evaluate the biocatalytic potential of different lineage of microorganisms and enzymes in the synthesis of compounds β-aminoketonic through Mannich reaction it was proposed the use of some enzymes such as: lipase, Lipozyme® and chymosin. The reactions were kept under stirring at room temperature from 24 to 48 hours in those which the enzymes were used like catalysts. All the reactions were monitored by thin layer chromatography. The crude of the reaction was purified on a silica gel column (70-230 mesh) and the obtained compounds were characterized by infrared spectroscopy, gas chromatography and nuclear magnetic resonance. All the reactions biocatalyzed by enzymes showed biocatalytic potential, but their concentration, the basicity of the amine and the reaction medium interfered in the reaction yield. The both three enzymes presented a higher affinity as for the less polar solvents (THF) as for the higher polar solvents (DMSO). However it was proposed the introduction of new low cost biocatalysts and environmentally safe on Mannich reactions.

Biosynthesis of some Mannich bases

The Mannich reaction is extremely useful to form molecules that contain nitrogen groups. Currently, there is a great interest turned to this class of compounds due to its biological properties. The recent literature reports that the utilization of enzymes can be an adequate methodology on this type of reaction. According to the exposed above and with the intention of synthesizing the -aminoketones, some catalysts like Chymosin and also some microorganisms such as Saccharomyces cerevisiae, (sourdough bread) and Lactobacilos (ATCC 90827LA10N19.10-E.U.A) were applied. These reactions were carried out by using water as solvent at room temperature excelling for the Green Chemistry principles. Figure 1 shows the reaction scheme involving 1 eq.mol of aniline, 1,3 eq.mol of formaldehyde, 10 ml of water and 0,25g of the catalyst during four days. The reaction furnished satisfactory yields which are in accordance with the literature data.

Sinthetic study of some beta-aminoketones using thiazolidine as catalyst

Mannich reaction is one of the most widely used in organic chemistry. In this reaction, there is a insertion of a aminomethyl group on the α position to the carbonyl group. Such reaction has numerous applying in organic chemistry in the synthesis of product with biological interest, such as analgesics and antibiotics. To form the Mannich’s bases a catalyst is needed and, with this purpose, the thiazolidines were used. Thiazolidines are cyclic compounds of five members which contain on the position 1 the sulphur atom and on the position 3 the nitrogen one. All the reactions were carried out at room temperature involving cyclopetanone, formaldehyde and various imines (aniline, p-chloroaniline and p-toluidine) (Scheme 1). The products of interest were satisfactorily obtained and their structures were confirmed through spectrometric methodologies.