Human population growth and development has been largely dependent on non-renewable natural resources, which cannot be indefinitely sustained. Beyond, coal and other abundant resources cannot continue to be used at current rates due to their impact on the environment and climate. It is thus important to replace as much as possible the fossil fuels and scarce minerals as sources of energy and industrial raw materials. Biomass plays a key role in this scenario, since its availability depends on abundant but often misused resources: air, water, sunlight and land. The “oil shocks”, the recognition of impending resource shortages, the global pollution and climate change led many governments and organizations to create roadmaps to Bioeconomy. This includes the growing use of plants and animals to produce energy and raw materials, but it cannot create food scarcity. Agriculture depends on the plant macronutrients N, P and K, and this article discusses their role in plant and animal growth, production and consumption, dependence on non-renewable minerals and energy and perspectives for increasing their efficiency. Special attention is given to Brazilian agriculture that is heavily dependent on imported NPK, requiring strategic action and research.
Abstract: Sustainable production requires increasing use of raw materials from renewable sources, processed under mild conditions with minimal effluent production. These requirements are satisfied by using materials derived from biomass, in synergy with food and energy production. The possibilities of biomass are continuously enlarged by new findings, as in the intrinsic nanocomposite properties of natural rubber and the amphiphile behavior of cellulose that translated into new functional materials, including high-performance, flexible and conductive non-metallic materials. Other findings are allowing a better understanding of electrostatic phenomena that play a positive role in electrostatic adhesion and cohesion of nanocomposites made from biomass products. Moreover, this should allow the development of safe electrostatic separation techniques, suitable for the fractionation of crude mixtures of biomass residues. A current study on rubber electrostatics is showing its capabilities as a transducer of mechanical energy while providing clues to understand the performance of the dielectric elastomers used in robotic self-sensing actuators.
This work describes the preparation, characterization and properties study of multifunctional nanocomposites between poly(styrene-co -butyl acrylate) latex and different carbon nanostructures: iron-filled carbon nanotubes (CNT), graphene or graphene oxide. Different approaches were employed to prepare stable aqueous dispersions of these nanostructures, according to the specificity of each nanomaterial. The nanocomposites were characterized by Raman and Fourier transform infrared (FTIR) spectroscopy, as well as by scanning probe microscopy (SPM) at different modes, providing information regarding the nature of the interaction between the carbon nanostructures and the polymeric matrix. The synergistic effect between the components results in improved mechanical, electrical, thermal and chemical properties of the nanocomposites, when compared to the neat polymer. In addition, the iron species into CNT cavities provide an interesting and unusual magnetic property of the nanocomposites. Results show that the properties of the nanocomposites can be modulated aiming desired application by simply selecting the amount and/or the kind of carbon nanostructure. This work provides information on the features of the three systems used, showing the range of properties that can be covered by using the three nano-fillers.
The Brazilian chemical community shows positive characteristics that improved significantly during the past forty years: the scientific output is substantial, it contributes positively to the position of this country in the innovation rankings, the chemical companies create and export technologies and the larger share of post-graduates employed by the Brazilian industry works in chemical or chemistry-based companies. The chemical sector is thus an exception within the country, together with agrosciences. These facts are unexpected, considering that chemical companies do not occupy leading positions in the rankings based on patent filing and other innovation indicators, throughout the world. This article describes the context of Brazilian chemistry in the middle 1970s, the the well-designed government actions that mobilized academic researchers and industry professionals to build complex converging scenarios and a positive S&T culture that is matched in few other areas, in this country.
Many reports associate electrostatic charge in dielectrics with water, either bulk, finely dispersed in aerosol or as atmospheric vapor. Two widespread but currently controversial assumptions relevant to this topic are the prevalence of electroneutrality and the passive role of water in electrical phenomena, dissipating charge due to its significant electrical conductivity. Early reports from Faraday, Kelvin and their contemporaries also point towards an active role of water as an electrifying agent. Unfortunately, these have been largely ignored or treated as scattered pieces of scientific curiosity, for over a century. New trends in this area have been developing since the late 1990s, due to a number of findings leading to radically new ideas. These derive from the experimental demonstration of widespread occurrence of non-electroneutral water and from charge partition associated with a number of interfacial phenomena, even in electrically shielded environments within grounded enclosures. This is an account on the formation and persistence of electrified water in various natural or anthropic environments, followed by experimental results obtained under well-defined conditions that are revealing different mechanisms for the role of water in charge acquisition and dissipation in dielectrics.
Gold nanoparticles (AuNPs) were synthesized by reduction of HAuCl4 with NaBH4 or l-ascorbic acid and they were stabilized with cysteine, cysteamine and a thiol-capped PEG. A nanocomposite was prepared by the addition of polylactic acid (PLA) acetone solutions to aqueous AuNP dispersions, resulting in PLAs enclosing AuNPs. Superparamagnetic iron oxide nanoparticles (SPION) modified with Au on the surface (SPION@Au NP) were synthesized. SPIONs were prepared by using iron-oleate as a precursor or by co-precipitation of ferrous and ferric chlorides in alkaline solution and, then used for seed-mediated growth of gold layers on their surfaces. The various nanoparticles were characterized by using UV-Vis spectroscopy, electron spectroscopy imaging/transmission electron microscopy (ESI/TEM) and by thermogravimetric analysis (TGA). The magnetic products were tested in a magnetic resonance imaging (MRI) scanner of high clinical field with results that indicate their promising utilization as contrast agents for MRI analysis.
Nanopartículas de Au (AuNP) foram sintetizadas por redução do HAuCl4 com NaBH4 ou ácido l-ascórbico, tendo sido estabilizadas por cisteína, cisteamina e PEG-SH. Com AuNPs, preparou-se um material nanocompósito através da precipitação de soluções acetônicas de ácido poliláctico (PLA), em dispersões aquosas de AuNPs, com obtenção de PLAs completamente impregnados por AuNPs. Nanopartículas de óxido de ferro superparamagnéticas (SPION) modificadas com Au na superfície (SPION@Au NP) foram sintetizadas. SPIONs foram sintetizadas usando-se oleato de ferro como precursor ou pela co-precipitação dos cloretos férrico e ferroso em solução alcalina, com posterior recobrimento das SPION por uma camada de ouro. Os produtos obtidos foram caracterizados por espectroscopia UV-Vis, microscopia de transmissão eletrônica com mapeamento elementar espectroscópico (ESI/TEM) e por análise termogravimétrica (TGA). Em particular, os produtos magnéticos foram testados em um aparelho de ressonância magnética por imagem (MRI) de alto campo clínico. Os resultados obtidos indicaram sua promissora utilização como meios de contraste em análises por MRI.
The transition to sustainable standards of production and consumption within a scenario of decreased availability of natural resources, growing population and climate change is essential to meet current challenges facing mankind. A strategy to meet these challenges should contain elements different from current approaches for industrial production. This work concentrates on the possibilities for the intensive use of sustainable biomass, abundant minerals and every type of residue, a task that can largely benefit from the application of nanotechnology and biotechnology platforms for material design and transformation. This strategy cannot be solely based on existing knowledge and requires new science, new knowledge including supposedly well-known themes, like the tribochemistry of electrostatic charging and friction. It is especially relevant within the Brazilian context, where many recent successful innovations are related to biomass production and transformation. Implementation of this strategy requires converging efforts by personnel from many different organizations and professions, while making sound risk assessment to produce significant innovation leading to sustainable development.
The main objective of this paper is to start and stimulate reflection, discussion and proposing actions that allow Chemistry in Brazil contribute to a prosperous, safer and better future for the nation.
Electrostatic phenomena were discovered long ago but their interpretation according to well-established atomic-molecular theory is still lacking. As a result, electrostatic phenomena are often irreproducible and uncontrolled, causing serious practical problems. Highly reproducible recent experimental results on electrostatic charging from this and other laboratories are reviewed in this work, together with a description of the relevant but not so usual Kelvin probe and Faraday cup techniques. These results support a new model for electrostatic charging of dielectrics and insulated metals, based on the role of moist atmosphere as a charge reservoir.