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The topic "Green Chemistry" has gained great importance over recent years, being quoted in an increasing number of publications. This fact shows how concern over developing "greener" processes has played a prominent role in the scientific community. In this context, the scope of this work encompasses an analysis of the evolution of the theme since its conception to the present. This analysis elucidates how bibliographic output on "Green Chemistry" is distributed worldwide. Moreover, the main journals on the subject were listed and ranked, according to impact factor.

The fundamental concepts of the green chemistry are highlighted in order to present the enormous number of challenges to develop a new chemistry in research, industry and education. The practice of an environmental friendly chemistry are presented to improve the economics of chemical manufacturing and to enhance the much-tarnished image of chemistry and to present the opportunities to discover and apply this new chemistry. The challenges and opportunities of green chemistry in the world and Brazil are introduced and discussed in this report.

Donor-acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers ( 1- 5) were synthesized from mono- or dialdehydes by a simple metal-free procedure. Cyclic voltammetry and UV/Vis absorption spectroscopy show that the extension and/or increase of the donor strength of the spacer produces a decrease of the HOMO and LUMO energy level, a red shift of the absorption spectrum and an increase of the molecular absorption coefficient. Compared to solutions, the optical spectra of spin-cast thin films of compounds 1-3 show a broadening and red shift of the absorption bands, consistent with the formation of J-aggregates. In contrast the blue shift observed for the EDOT-containing compounds 4 and 5 suggests the presence of H-aggregates. Solution-cast and vacuum-deposited films of donors 1-5 were evaluated in solar cells with fullerene C60 as acceptor. A power-conversion efficiency among the highest reported for bilayer devices of basic configuration was obtained with compound 2. On the other hand, the results obtained with 4 and 5 suggest that the presence of EDOT in the structure can have deleterious effects on the organization and performances of the donor material. [ABSTRACT FROM AUTHOR]

The use of low-cost and eco-friendly adsorbents has been investigated as ideal alternatives to the current expensive methods for removing dyes from waste water. Orange peel (OP) was used as a low cost natural waste adsorbent for the removal of textile effluents. The effectiveness of (OP) in adsorbing; C.I. Direct Red 79 (DR 79) and C.I. Direct Yellow 27 (DY 27) from their dye baths has been studied as a function of pH, solid/liquid ratio, agitation time and initial dye concentration. The sorption isotherms were analyzed using Langmuir and Frendlich models. The results indicated that acidic solutions supported the adsorption of the studied dyes within (OP). Adsorption kinetic models were analyzed using the pseudo-first, second order equation and intraparticle diffusion equation. The results showed that the order equation fitted the experimental data very well. By the way, the effect of adsorbent surface was analyzed by scanning electron microscope (SEM), whereas the SEM images showed reasonable agreement with adsorption measurements. [ABSTRACT FROM AUTHOR]

Abstract: Conjugated polymers of hybrid structure containing cyanovinylene linkages have been synthesized by Knoevenagel condensation of diformyl terthienyls with para-dicyanomethylbenzene. UV–vis and cyclic voltammetric data show that these polymers combine reduced band gap, improved light-harvesting properties and low lying HOMO level. Whereas the very low solubility of the polymers did not allow the fabrication of bulk heterojunction solar cells, bilayer heterojunction solar cells have been realized using thermally evaporated films of fullerene C60 as acceptor material. The best devices show a maximum external quantum efficiency of ∼20% and a power conversion efficiency of 0.40% under simulated AM 1.5 solar illumination. [Copyright &y& Elsevier]

Abstract: The principles of green chemistry are applied to not only chemical engineering and synthesis, but also increasingly analytical chemistry. We describe environment-friendly analytical techniques applied to isolate and to enrich trace organic pollutants from solid and aqueous samples. Amounts of organic solvents used in analytical laboratories are reduced by applying solventless extraction, extraction using other types of solvent, assisted solvent extraction and miniaturized analytical systems. [Copyright &y& Elsevier]

The literature about direct solid sampling (SS) and slurry sampling atomic absorption spectrometry (AAS) over the past decade has been surveyed critically. It became apparent that a very significant change had occurred, particularly in the relation between the two major techniques used for that purpose. In the 1990s, slurry sampling was typically considered the technique of choice, combining the significant advantages of the solid and the liquid sampling methods, at least in part because of the availability of a commercial accessory for automatic slurry sampling. The situation is completely inverted now, as the above accessory has been discontinued and rugged and reliable accessories for direct SS became available. Direct SS electrothermal (ET) AAS has been shown to provide the best limits of detection because of the absence of any dilution and a minimal risk of contamination. Calibration against aqueous standards appears to be feasible after careful program optimization. The absence of any significant sample handling makes SS ET AAS ideally suited for fast screening analyses. The introduction of high‐resolution continuum source AAS appears to open additional attractive features for SS ET AAS because of the significantly simplified optimization of furnace programs and the visibility of the spectral environment, which makes it easy to avoid spectral interferences. New calibration strategies make a “dilution” of samples unnecessary, which used to be one of the major limitations of SS ET AAS. Finally, direct SS analysis is an important contribution to clean chemistry, as practically no reagents are used. [ABSTRACT FROM AUTHOR]

The beginning of green chemistry is frequently considered as a response to the need to reduce the damage of the environment by man-made materials and the processes used to produce them. A quick view of green chemistry issues in the past decade demonstrates many methodologies that protect human health and the environment in an economically beneficial manner. This article presents selected examples of the implementation of green chemistry principles in everyday life in industry, the laboratory and in education. A brief history of green chemistry and future challenges are also mentioned. [ABSTRACT FROM AUTHOR]