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We have developed carbon quantum dots (CQDs) with excellent photoluminescence (PL) properties from macaúba (Acrocomia aculeate) fibers; a widely available cellulosic biomass species of palm trees in South America. As-prepared CQDs showed quasi-spherical morphology with high aqueous solubility and strong excitation-dependent fluorescence behaviour. Interestingly, the CQDs display fluorescence 'turn-off' response with excellent sensitivity toward multi-metal ions including Fe3+, Cu2+ and Hg2+ with very low detection limits of 0.69 μM, 0.99 μM, 0.25 μM, respectively. Notably, ascorbic acid (AA) induced a change in the (turn-off) fluorescence of Fe3+-CQDs, which caused an almost 70% revival of fluorescence (turn-on) by displacing Fe3+ ions. We have also harnessed CQDs as the visible-light-induced photocatalyst to reduce CO2 in water. Especially, the CQDs efficiently promote the photocatalytic reduction of CO2 into methane (CH4) with an evolution rate of 99.8 nmol/g at 436 nm in aqueous conditions. This indicates that the CQDs provide abundant active sites for CO2 adsorption and thus enhance the separation and migration of photo-induced charge carriers that efficiently reduce CO2 into CH4 without any co-catalyst in 100% water. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop polymer blends of plasticized thermoplastic waxy starch (TPS) and poly(ɛ-caprolactone) (PCL) using the largest amount of TPS possible to obtain a biodegradable material motivated by sustainability issues and to replace petrochemical-based polymers with alternatives based on biopolymers. Addition of TPS to other polymers has been used to obtain cheaper and increasingly biodegradable final products. However, TPS presents limited mechanical properties, and mixing with other polymers such as PCL is necessary to overcome these limitations and improve its processability. TPS was processed by extrusion and thermo-compression using 30 wt% glycerol. The blends were suitably processed by extrusion and further injected. The TPS/PCL blends were studied by varying the amount of PCL in a range of 10 wt% in increasing order of addition. Thermal analysis showed that introducing PCL in TPS increased Tonset because of the higher thermal stability of the former, and that the obtained blends presented a behavior intermediate to that of neat polymers. [ABSTRACT FROM AUTHOR]

Bone defects stand out as one of the greatest challenges of reconstructive surgery. Fused deposition modelling (FDM) allows for the printing of 3D scaffolds tailored to the morphology and size of bone damage in a patient-specific and high-precision manner. However, FDM still suffers from the lack of materials capable of efficiently supporting osteogenesis. In this study, we developed 3D-printed porous scaffolds composed of polylactic acid/hydroxyapatite (PLA/HA) composites with high ceramic contents (above 20%, w/w) by FDM. The mechanical properties of the PLA/HA scaffolds were compatible with those of trabecular bone. In vitro degradation tests revealed that HA can neutralize the acidification effect caused by PLA degradation, while simultaneously releasing calcium and phosphate ions. Importantly, 3D-printed PLA/HA did not induce the upregulation of activation markers nor the expression of inflammatory cytokines in dendritic cells thus exhibiting no immune-stimulatory properties in vitro. Evaluations using human mesenchymal stem cells (MSC) showed that pure PLA scaffolds exerted an osteoconductive effect, whereas PLA/HA scaffolds efficiently induced osteogenic differentiation of MSC even in the absence of any classical osteogenic stimuli. Our findings indicate that 3D-printed PLA scaffolds loaded with high concentrations of HA are most suitable for future applications in bone tissue engineering. [ABSTRACT FROM AUTHOR]

New materials can be developed using a known compound with enhanced properties modifying and controlling its microstructure, morphology, and density of defects. In this work, a new material was produced by the addition of ionic liquid (IL) to the poly(o-methoxyaniline) (POMA) conductive polymer, in the form of esmeraldine salt. The polymer impregnated with IL was tested as an electrode for use in supercapacitors. The results show that the charge storage properties of the materials are dependent on the length of the alquil substituent of imidazolium ring of ionic liquid cation. The best results, obtained by the addition of 1-butyl-3-methylimidazolium triflate IL to the polymer, improved electrical charge storage and electrochemical stability, making the material a promising electrode for supercapacitor devices. This compound has specific capacitance of 205 F/g, five times larger than pure POMA and was stable for 3000 cycles of charge/discharge experiments carried out at 1.0 A/g. Graphical Abstract [ABSTRACT FROM AUTHOR]

PAAm–MC hydrogels as a potential delivery vehicle for the controlled release of paraquat pesticide was investigated, as they play an essential role to use hydrogels in controlled release technology. The release kinetics of paraquat was determined using UV–Vis measurements. The release mechanism of paraquat from PAAm–MC hydrogels was investigated through a semi-empirical model proposed by Ritger and Peppas. In general, the initial rate of paraquat release was fast, decreasing after several days, hence indicating that paraquat on the surface (or close to) of hydrogels diffused rapidly after the initial swelling of the gel. Later, the cumulative release occurred in a very controlled and sustained manner, with the paraquat concentration maintaining constant from 15 to 46 days. The paraquat release capacity was dependent on the swelling of the matrix and the density of the network chains. The curves obtained from Peppas’s model presented good linearity ( R2 ≥ 0.999), indicating that such model can be applicable to analyze the systems. The n values for the pesticide release from hydrogels indicate that paraquat release has Fickian and non-Fickian diffusion, depending of hydrogel formulation. The values of k showed that the release of paraquat becomes slower when the MC and AAm concentration increases. Finally, to the best of our knowledge, we report a hydrogel-based vehicle (first carrier) that is able to prolong the sustained release of paraquat pesticide up to 45 days, which is essential for its application in controlled release systems. [ABSTRACT FROM AUTHOR]

Due to the increasing search for alternative sources of natural rubber (NR) whose properties are similar to Hevea brasiliesis, several sources have been studied in the past few years. Among them, Mangabeira ( Hancornia speciosa Gomes), which is native to Amazon rainforest and other regions of Brazil, has a potential as another viable rubber source. As a continuation of a series of comparative studies between Hancornia and Hevea (clone RRIM 600) these two species by our research team, their thermal behavior was analyzed by thermogravimetry (TG) using Flynn–Wall–Ozawa’s approach in order to obtain kinetic parameters (reaction order, pre-exponential factor and activation energy) of the decomposition process. Results indicated that the thermal behavior of NR from Hancornia was comparable to Hevea with some differences observed as follows: reaction order for Hancornia was higher than for Hevea at the beginning of degradation and very close for temperatures over 350 °C; activation energy and pre-exponential factor had the same trend, i.e., increased with increasing degree of conversion remaining almost constant between 20 and 70% and then increasing for higher degrees, although Hevea was slightly more thermally stable than Hancornia. These major influences in the degradation process in the early stage are attributed to differences in non-rubber constituents present in these two species. [ABSTRACT FROM AUTHOR]

Coconut, sisal and jute fibers were added as reinforcement materials in a biodegradable polymer matrix comprised of starch/gluten/glycerol. The content of fibers used in the composites varied from 5% to 30% by weight of the total polymers (starch and gluten). Materials were processed in a Haake torque rheometer (120 °C, 50 rpm) for 6 min. The mixtures obtained were molded by heat compression and further characterized. Addition of lignocellulosic fibers in the matrix decreased the water absorption at equilibrium. The diffusion coefficient decreased sharply around 5% fiber concentration, and further fiber additions caused only small variations. The thermogravimetric (TG) analysis revealed improved thermal stability of matrix upon addition of fibers. The Young’s modulus and ultimate tensile strength increased with fiber content in the matrix. The storage modulus increased with increasing fiber content, whereas tanδ curves decreased, confirming the reinforcing effect of the fibers. Morphology of the composites analyzed under the scanning electron microscope (SEM) exhibited good interfacial adhesion between the matrix and the added fibers. Matrix degraded rapidly in compost, and addition of increased amounts of coconut fiber in the matrix caused a slowdown the biodegradability of the matrix. [ABSTRACT FROM AUTHOR]

The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly( o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH=3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasi-one dimensional variable range hopping (VRH) mechanism. [ABSTRACT FROM AUTHOR]

In this article the author discusses the potential effects of volcanic ash cloud originating in Iceland and covering large areas of Europe.