Aplicações de fibras lignocelulósicas na química de polímeros e em compósitos

The use of lignocellulosic fibers and their constituents, as raw materials in the production of polymeric and composite materials, represent an exceptional opportunity of sustainable technological development. In the present report works that discuss promising alternatives of obtaining and use of materials such as cellulose, hemicellulose, lignin, cellulose nanocrystals and biocomposites were revised. The advance in the use of biomass can be, in a near future, capable of going beyond the application difficulties of these vast materials, especially in relation to the economical unviability, by the production of high performance polymeric and composite materials. This advance would represent a higher profitability to some areas of agrobusiness, especially the sector of biofuels, which produces elevated amounts of biomass waste.

Cromatografia de afinidade por íons metálicos imobilizados (IMAC) de biomoléculas: aspectos fundamentais e aplicações tecnológicas

Immobilized Metal Ion Affinity Cromatography - IMAC - is a group-specific based adsorption applied to the purification and structure-function studies of proteins and nucleic acids. The adsorption is based on coordination between a metal ion chelated on the surface of a solid matrix and electron donor groups at the surface of the biomolecule. IMAC is a highly selective, low cost, and easily scaled-up technique being used in research and commercial operations. A separation process can be designed for a specific molecule by just selecting an appropriate metal ion, chelating agent, and operational conditions such as pH, ionic strength, and buffer type.

Efeito da aplicação de nitrato na redução biogênica de sulfeto sob diferentes concentrações iniciais de bactérias redutoras de nitrato e sulfato

The effect of sodium nitrate application in the reduction of biogenic sulphide was evaluated through a 2k complete factorial design, using as variable response the production of sulfide at intervals of incubation of 7, 14 and 28 days. The most effective condition for reducing the sulphide production (final concentrations from 0.4 to 1.6 mg S2- L-1) was obtained with an initial population of sulphate-reducing bacteria and nitrate-reducing bacteria of 10(4) MPN mL-1 and 427.5 mg L-1 nitrate. The results also suggested that the applications of nitrate to control the process of souring should follow a continuous scheme.

Fulereno[C60]: química e aplicações

Fullerene chemistry has become a very active research field in the two last decades, largely because of the exceptional properties of the C60 molecule and the variety of fullerene derivatives that appear to be possible. In this review, a general analysis of fullerene C60 reactivity is performed. The principal methods for the covalent modification of this fascinating carbon cage are presented. The prospects of using fullerene derivatives as medicinal drugs and photoactive materials in light converting devices are demonstrated.

Propriedades reológicas e efeito da adição de sal na viscosidade de exopolissacarídeos produzidos por bactérias do gênero Rhizobium

Viscosity of some polysaccharide solutions supports that these molecules can be applied in food sectors. Four exopolysaccharides (R1, R2, R3, R4) produced by different Rhizobium strains were selected. Sugar composition and differences in the uronic acid contents suggests that chemical structure of these molecules can vary when different culture conditions and strains are analyzed. The Power Law was the rheological model used to represent the experimental data of shear stress versus shear rate. All exopolysaccharides showed non-Newtonian behavior, with pseudoplastic characteristics. R1, R2 and R4 showed a slight increase in viscosity in the presence of 0,2 M NaCl.

Voltametria de micropartículas imobilizadas: fundamentos e aplicações analíticas

The theoretical aspects of Voltammetry of Immobilized Microparticles (VIM) were discussed. The immobilization of microparticles on electrode surface, the electrode cleaning processes and the electrode materials were analyzed. The three-phase electrode model and the possible reactions between the immobilized particle and the electrolytic solution were discussed. In addition, this work discusses some selected applications of VIM published in the last years.

Oligômeros e polímeros derivados do tiofeno: síntese e aplicações

In this review we summarize recent synthetic investigations about the preparation of oligothiophenes and polythiophenes, the most important π-conjugated organic materials for applications in electrochromic and electroluminescent devices. It is showed that many interesting and novel functionalized oligothiophenes have been synthesized by convenient coupling strategies (Heck, Kumada, Negishi, Suzuki, Stille and Ullmann) and oxidative coupling methods. Synthesis of polythiophenes are also presented and described according to chemical and electrochemical polymerization methodologies. The description of these noteworthy synthetic methods illustrates how important and promising are the interdisciplinary approaches in the obtaining of oligothiophenes and polythiophenes.

Eletrodos modificados por hidróxido de níquel: um estudo de revisão sobre suas propriedades estruturais e eletroquímicas visando suas aplicações em eletrocatálise, eletrocromismo e baterias secundárias

The present review paper describes the main features of nickel hydroxide modified electrodes covering its structural and electrochemical behavior and the newest advances promoted by nanostructured architectures. Important aspects such as synthetic procedures and characterization techniques such as X-Ray diffraction, Raman and Infrared spectroscopy, Electronic Microscopy and many others are detailed herein. The most important aspect concerning nickel hydroxide is related to its great versatility covering different fields in electrochemical-based devices such as batteries, electrocatalytic systems and electrochromic electrodes, the fundamental issues of these devices are also commented. Finally, some of the newest advances achieved in each field by the incorporation of nanomaterials will be shown.

Cromatografia gasosa ultrarrápida: uma visão geral sobre parâmetros, instrumentação e aplicações

Since the introduction of GC there has been an ongoing interest in reducing time of analysis resulting in new terms and definitions such as ultra fast gas chromatography (UF-GC). One of the most used definitions describes UF-GC as a technique that combines the employment of short narrow bore column with very fast temperature programming rates producing chromatographic peaks in the range of 50 ms and allowing separations times in 1-2 min or less. This paper summarizes the analytical approaches, the main parameters involved and the instrumentation towards UF-GC.

Recentes aplicações sintéticas de compostos orgânicos tricloro(bromo)metila substituídos

This review presents the recent applications of some trihalomethyl carbinols, α,α,α-trihalogenated carbonyl compounds and trichloro(bromo)methyl-containing heterocycles, acting as high versatile synthetic precursors in organic chemistry, based on the last 10 years' literature.

Aplicações de cromatografia líquida de alta eficiência para o estudo de poluentes orgânicos emergentes

Emerging organic pollutants (EOP) include many environmental contaminants based on commercial products such as pharmaceuticals, personal care products, detergents, gasoline, polymers, etc. EOP may be candidates for future regulation as they offer potential risk to environmental and human health due to their continual entrance into the environment and to the fact that even the most modern wastewater treatment plants are not able to totally transform / remove these compounds. High performance liquid chromatography is recommended to separate emerging organic pollutants with characteristics of high polarity and low volatility, especially pharmaceuticals, from environmental matrices.

Cromatografia líquida capilar: estado da arte e aplicações

This review describes the advantages and disadvantages of using capillary liquid chromatography (CLC), which is considered the newest member in the analytical separation science arsenal. Although CLC has tremendous potential for being the next major innovation in separatory analysis, it has not yet obtained great popularity compared to conventional high performance (and ultra-high performance) liquid chromatography. Comparisons are made between these techniques and some of the reasons that CLC has not yet reached its potential will be advanced.

Aplicações sintéticas do ácido mucobrômico e da 3,4-dibromofuran-2(5H)-ona

This review describes the use of two biomass-derivate butenolides as intermediates in organic synthesis, mucobromic acid and its reduced derivative 3,4-dibromofuran-2(5H)-one. The ambiphilic and ambident character of such butenolides make them versatile starting materials in the synthesis of natural and/or bioactive compounds. Thus, the reactions of mucobromic acid with C-nucleophiles and heteronucleophiles are described, as well as the nucleophilic addition to carbonyl reactions of 3,4-dibromofuran-2(5H)-one. Besides, both compounds are active in diverse metal cross-coupling reactions, manly with palladium in Suzuki and Sonogashira reactions.

Nanocompósitos magnéticos: potencialidades de aplicações em Biomedicina

The synthesis of magnetic materials such as nanostructured iron oxide has been intensively researched due to their broad applications in biomedicine. As these nanoparticles have high specific surface area, they are very reactive and can aggregate easily, and biodegrade when exposed to biological systems. Mesoporous silica is often employed as support matrix to protect the magnetic functional component, avoiding undesirable effects. In this context, this review describes various syntheses of silica-coated iron oxide nanoparticles, and their use in applications such as bioseparation, magnetic resonance imaging, hyperthermia and drug delivery systems showing the growing interest of these materials in biological area.

Mecanismos envolvidos na biodegradação de materiais lignocelulósicos e aplicações tecnológicas correlatas

The biodegradation of lignocellulosic materials is an important natural process because it is responsible for the carbon recycling. When induced under controlled conditions, this process can be used for technological applications such as biopulping, biobleaching of cellulosic pulps, pre-treatment for subsequent saccharification and cellulosic-ethanol production, and increase of the digestibility in agroindustrial residues used for animal feed. In the present work, the enzymatic and non-enzymatic mechanisms involved in the biodegradation of lignocellulosic materials by fungi were reviewed. Furthermore, the technological applications of these extracellular metabolites are presented and discussed.