Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that has reported on the use of these technologies for pretreatment of various lignocellulosic biomasses.

Nanoscience has matured significantly during the last decade as it has transitioned from bench top science to applied technology. Presently, nanomaterials are used in a wide variety of commercial products such as electronic components, sports equipment, sun creams and biomedical applications. There are few studies of the long-term consequences of nanoparticles on human health, but governmental agencies, including the United States National Institute for Occupational Safety and Health and Japan’s Ministry of Health, have recently raised the question of whether seemingly innocuous materials such as carbon-based nanotubes should be treated with the same caution afforded known carcinogens such as asbestos. Since nanomaterials are increasing a part of everyday consumer products, manufacturing processes, and medical products, it is imperative that both workers and end-users be protected from inhalation of potentially toxic NPs. It also suggests that NPs may need to be sequestered into products so that the NPs are not released into the atmosphere during the product’s life or during recycling. Further, non-inhalation routes of NP absorption, including dermal and medical injectables, must be studied in order to understand possible toxic effects. Fewer studies to date have addressed whether the body can eventually eliminate nanomaterials to prevent particle build-up in tissues or organs. This critical review discusses the biophysicochemical properties of various nanomaterials with emphasis on currently available toxicology data and methodologies for evaluating nanoparticle toxicity.

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Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution and stabilized by polyvinyl alcohol (PVA) were synthesized. The particles were prepared by a coprecipitation technique using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Using a design of experiments (DOE) approach, the effect of different synthesis parameters (stirring rate and base molarity) on the structure, morphology, saturation magnetization, purity, size, and size distribution of the synthesized magnetite nanoparticles was studied by various analysis techniques including X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC) measurements, vibrating-sample magnetometer (VSM), transmission electron microscopy (TEM), UV-visible, and Fourier transform infrared (FT-IR) spectrometer. PVA not only stabilized the colloid but also played a role in preventing further growth of SPION followed by the formation of large agglomerates by chemisorption on the surface of particles. A rich behavior in particle size, particle formation, and super paramagnetic properties is observed as a function of molarity and stirring conditions. The particle size and the magnetic properties as well as particle shape and aggregation (individual nanoparticles, magnetic beads, and magnetite colloidal nanocrystal clusters (CNCs) are found to be influenced by changes in the stirring rate and the base molarity. The formation of magnetic beads results in a decrease in the saturation magnetization, while CNCs lead to an increase in saturation magnetization. On the basis of the DOE methodology and the resulting 3-D response surfaces for particle size and magnetic properties, it is shown that optimum regions for stirring rate and molarity can be obtained to achieve coated SPION with desirable size, purity, magnetization, and shape.

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In this work we employed the layer-by-layer adsorption technique for deposition on solid substrates of polyionic films containing photoactive azobenzene groups. We investigated two systems, each having the same polyanion but using a different polycation. Poly {1-4[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl sodium salt} (PAZO) was employed as the photoactive polyanion; poly(diallyldimethylammonium chloride) (PDDA) and poly(ethyleneimine) (PEI) were used as the polycations. Our phenomenological data show dramatic differences in the behavior of the two systems, although the same experimental conditions were employed in both cases. The assembly of the multilayers was monitored by ellipsometry and X-ray reflectivity via thickness measurements. We observed a considerable difference in the bilayer thickness in the two systems. An average polycation/polyanion bilayer thickness of 5 Å was measured for PDDA/PAZO, while the PEI-containing system resulted in a 36 Å thick bilayer. We used quartz crystal microbalance (QCM) measurements and UV−visible spectroscopy to monitor the adsorption process. QCM measurements showed an influence of the polycation in the polyanion adsorption process of the PAZO molecules. In particular, PEI appears to promote complexation and aggregation of the negatively charged polyion. Aggregates, mainly in the J form, were detected in both PDDA/PAZO and PEI/PAZO systems by UV−visible spectroscopy. We induced trans-to-cis photoisomerization of the azobenzene groups by UV light (340 nm), and we followed the photoreaction by the decrease in the intensity of the π−π* band, which is associated with the trans form of the azo molecules. The photoreaction apparently did not reach completion because the π−π* band did not completely disappear. We found also that the polycations have a significant influence on the molecular orientation of the azobenzene groups in the film and on the photoisomerization kinetics. The kinetics of photoisomerization were not monoexponential, indicating the coexistence of different processes. We investigated also the cis-to-trans reverse isomerization. In particular, we observed a partial recovery of the π−π* band after thermal relaxation that was more significant in the PDDA-containing system. By contrast, cis-to-trans isomerization induced by blue light (460 nm) was not observed. UV light irradiation was responsible for reversible changes in the optical thickness of the films, defined as n × d, where n is the refractive index and d is the overall thickness of the film.