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We present a highly efficient single‐atom catalyst (SACs) tailored for nitroarene reduction using NaBH4 under ambient conditions. Employing an unique approach, we harnessed NaCl under high temperature to create host materials enriched with negatively charged nitrogenous and oxygenated functional groups, capable of anchoring and stabilizing Ni ions within the aromatic structure. The nickel single sites were prepared by a straightforward cation exchange method. STEM‐HAADF imaging confirmed the presence of nickel single‐atoms, while XPS, FTIR, and Raman spectra validated nickel coordination within the catalyst. Remarkably, the CN−Ni catalyst exhibited exceptional catalytic performance under ambient conditions, achieving a high catalytic activity with NaBH4 (TOF 2246± ${\pm }$ 452 h−1 and 107± ${\pm }$ 47 mmol g−1 min−1). It also demonstrated remarkable conversion exceeding 90 % and outstanding selectivity. Equally impressive was its ability to maintain full catalytic activity over multiple reaction cycles, highlighting its robustness. This work is a significant leap in SACs design, offering a versatile and highly effective preparation method for SACs based on N‐doped carbon with far‐reaching implications in industrial reduction reactions. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have emerged in the last few years as new carbon nanostructures due to their excellent optical and physicochemical properties and thus promising applications in different areas. In this work, we describe the preparation of different CDs obtained from distinct bottom-up methods and also using different low molar mass precursors in order to study advantages and disadvantages of each experimental method used. Different techniques were performed to characterize the nanoparticles, such as Transmission electron microscopy, Potentiometric titration, Fourier transform infrared, Fluorescence and Ultraviolet-visible spectroscopy. The CDs obtained using conventional hydrothermal carbonization showed the highest values of quantum yield (QY), whereas the nanoparticles obtained by the heating reflux reaction method exhibited the lowest QY values mainly due to incomplete polymerization and/or carbonization reactions of the material. In addition, a study to evaluate the use of the CDs as nanoprobes for metallic ions showed that one of the samples exhibited high selective and sensitive response toward Fe3+, with a detection limit of 0.89 µM. Furthermore, the nanoparticles used as sensors were obtained with an environmentally friendly strategy, and the CD-based photoluminescence method is simple, has a short response time and present low-cost. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) represent a rising class of nanomaterials with numerous optical and physicochemical properties that make them useful for a variety of applications. In this work, three different methods, conventional hydrothermal carbonization (CHC), microwave-assisted irradiation and heating reflux reaction technique, were used as different bottom-up approaches to obtain different CDs. The carbon nanoparticles were prepared using three different carbon precursors (maleic, fumaric and adipic acids) and one nitrogen source (ethylenediamine). The CDs were characterized using different techniques including Fourier transform infrared spectroscopy, Transmission electron microscopy, Ultraviolet-visible, Fluorescence and Zeta potential measurements. Both, the experimental method used to obtain the CDs and the different precursors, presented a considerable influence on the quantum yield values (QY), and also on the fluorescence emission curves. The molar proportion between the carbon and nitrogen source was varied to improve the QY, and one of the samples prepared by CHC method reached QY = 25.4%. The carbon nanoparticles obtained by CHC were used as nanoprobes for metal ions and exhibited great selectivity and sensitivity for Fe3+ ions, reaching a limit of detection of 35 nM, which is lower than most reported values for CD-based PL method used as probes for Fe3+ ions. [ABSTRACT FROM AUTHOR]

Chitosan and carboxymethyl chitosan-based hydrogels were prepared by crosslinking the biobased polymers with hexamethylene diisocyanate (HDI). The hydrogels were obtained in a simple one-pot route, using water as solvent, at room temperature and without the use of other additives. The obtained materials were characterized using Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TG/DTG), X-ray diffraction (XRD), elemental analysis (CHN) and scanning electron microscopy (SEM) techniques. The water absorption capacity and absorption kinetics were also studied at different pH values. The comparison between the hydrogels obtained from the different biopolymers showed remarkable differences including water absorption capacity (swelling ratio) which is up to ~ 15 for the chitosan-based hydrogel and reached ~ 64 for the carboxymethyl chitosan-based hydrogel. In addition, the morphologies obtained for each sample were also considerably different. The chitosan-based hydrogels did not present pores before the swelling process, and after that, only the presence of a heterogeneous pores structure was observed. On the other hand, for the CMC-based hydrogels a homogeneous porous structure was noticed before and after the swelling process, and a significant increase in pore size was observed after water absorption. Since the two kinds of hydrogels obtained here were prepared through an easy and efficient route, using water as solvent and present potential biodegradability, simultaneously with a good swelling capacity, particularly for the CMC-based hydrogels, the obtained materials can find application in different areas such as agricultural or biomedical. [ABSTRACT FROM AUTHOR]

The preparation of carbon dots (CDs) from different biomass source represents an interesting alternative to obtain these nanoparticles, mainly when they can be prepared using low-cost methods. In this work we have used a nitrogen-rich precursor, chitosan, to obtain CDs using two different methods, acid dehydration (AD) and hydrothermal carbonization (HC), with the aim to study the different characteristics of the obtained nanoparticles. Also, a simple method to functionalize the CDs was applied to enhance the optical properties of the carbon nanoparticles. The obtained CDs were characterized by several techniques including FTIR, Elemental Analysis, TEM, UV-Vis, Fluorescence, and Potentiometric Titration. Size distribution measurements showed that the CDs had a narrow size distribution, with the diameters in the range 1.0–3.6 nm. Also, the CDs obtained by the HC method showed a greater amount of nitrogen functional groups than the nanoparticles prepared by the AD route. The functionalized CDs obtained from the HC method reached 15.3% of quantum yield. Furthermore, the obtained CDs were used as fluorescent sensors for different metal ions. Finally, these results represent an alternative to obtain biomass-derived CDs prepared via a low-cost method, presenting a relatively high quantum yield with potential applications in different areas. [ABSTRACT FROM AUTHOR]

The objective of the present study was the preparation and characterization of poly(butylene adipate‐co‐terephthalate) (PBAT) and thermoplastic starch (TPS) blends reinforced with cellulose nanoparticles (CNCs) by extrusion. The work was conducted in four steps. Initially, the CNCs were prepared from eucalyptus cellulose pulp by acid hydrolysis. The second step was the preparation of the nanocomposite (TPS‐CNC), composed of cassava starch, CNC, glycerol, and citric and stearic acids, by double screw extrusion. The third step was the preparation of PBAT/TPS‐CNC blends in twin‐screw extruders. In the fourth step, the films were produced by flat extrusion. Blends exhibited similar rheological behavior, increasing the CNC concentration in blends increased the viscosity as a function of the shear rate, and altered the behavior of the shear storage (G′) and shear loss (G″) curves as a function of the oscillation frequency (ω). The presence of CNC in blend provided improvements significant in mechanical properties, with 120% increase in Young's modulus, and 46% increase in maximum tensile. Thermal behavior (thermogravimetric analysis and differential scanning calorimetry) was altered with the incorporation of the CNC, showing a single melt peak (Tm) and a slight increase in Tg, indicating good dispersion between the phases of the blends, corroborating with the fracture surface microscopy of films. [ABSTRACT FROM AUTHOR]

Copyright of Makara Journal of Science is the property of Universitas Indonesia, Directorate of Research & Community Engagement and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT Collagen (Col) is extensively used in various applications, including pharmaceutical, agricultural, and food applications. The materials based in Col may exhibit properties of biomedical interest because of their low toxicity, high structural capacity support, controlled biodegradability, and biocompatibility. However, Col has poor thermal and mechanical properties. The addition of plasticizers (Plas's) and fillers is an established strategy for enhancing the properties of the resulting nanocomposites. In this study, nanocomposites based on Col and cellulose nanocrystals were developed in two different ways and with three different Plas's. These materials were subjected to structural, thermal, mechanical, and morphological analysis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44954. [ABSTRACT FROM AUTHOR]

Copyright of Periódico Tchê Química is the property of Grupo Tche Quimica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: In this study cellulose nanowhiskers were obtained from balsa wood. For this purpose, fibers of balsa wood were exposed to hydrolysis reactions for lignin and hemicellulose digestion and acquisition of nano-scale cellulose. Transmission electron microscopy (TEM) results demonstrated that the obtained cellulose nanocrystals had average length and thickness of 176 (±68 nm) and 7.5 (±2.9 nm), respectively. Infrared spectroscopy (FTIR) and wide angle x-ray diffraction (WAXD) showed that the process for extracting the nanowhiskers digested nearly all the lignin and hemicellulose from the balsa fiber and still preserved the aspect ratio and crystallinity satisfactory enough for future application as nanofillers in polymer nanocomposites. The thermogravimetric analysis (TGA) showed that the onset temperature of thermal degradation of the cellulose nanocrystals (226 °C) was higher than the onset temperature of the balsa fiber (215 °C), allowing its use in molding processes with polymers melts. [ABSTRACT FROM AUTHOR]

The mesophase behaviour of a side-chain liquid crystalline polyacrylate (LCP) grown by drying a solution has been investigated. This LCP, characterised by a short spacer (four carbon atoms) and a long tail (10 carbon atoms), displays, at increasing temperatures, SmC and SmAd phases. The effect of the mean molecular weight, i.e. the mean number of side chains per polyacrylate main chain (18 and 51) on the lamellar width, was studied. LCP-silica nanocomposites have been synthesised by a sol-gel process in the presence of LCP in the solution, followed by subcritical drying. The mesophase behaviour of these nanocomposites was compared to that of the corresponding bulk LCP. The experimental methods were polarised optical microscopy, differential scanning calorimetry and synchrotron X-ray scattering. [ABSTRACT FROM AUTHOR]

About 85–90% of the market for new materials in biodegradable packaging is served by various blends and composites containing starch in some portion. In an attempt to satisfy the increasing consumer demand, innovative materials are being developed. This includes the concept of active packaging, which, in addition to protecting, interacts with the packaged product. In this context, flexible films have been prepared from blends of poly(butylene adipate‐co‐terephthalate), thermoplastic starch (TPS), and cellulose nanowhiskers (CNW) at different concentrations (0–3.0 wt %) and with distinct compatibilizing agents (glycerol, stearic acid, and citric acid) by flat extrusion. Palm oil was packaged in the films, and was stored under accelerated oxidation conditions as a model system. The films were also used for packing lettuce. The TPS increased the rate of water vapor permeability of the blends. The micrographs showed the films with very porous surface as a function of the CNW concentration. In addition to the antimicrobial action pronounced within 10 days (fungi—molds and yeasts; bacteria—mesophilic and psychrotrophic), the film showed a prooxidant action, indicating its suitability for fruit and vegetable packaging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47699. [ABSTRACT FROM AUTHOR]

Hydrogels have been studied as promising materials in different biomedical applications such as cell culture in tissue engineering or in wound healing. In this work, we synthesized different nanocellulose-alginate hydrogels containing cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals (CNCTs), cellulose nanofibers or TEMPO-oxidized cellulose nanofibers (CNFTs). The hydrogels were freeze-dried and named as gels. The nanocelluloses and the gels were characterized by different techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA), while the biological features were characterized by cytotoxicity and cell growth assays. The addition of CNCTs or CNFTs in alginate gels contributed to the formation of porous structure (diameter of pores in the range between 40 and 150 μm). TEMPO-oxidized cellulose nanofibers have proven to play a crucial role in improving the dimensional stability of the samples when compared to the pure alginate gels, mainly after a thermal post-treatment of these gels containing 50 wt % of CNFT, which significantly increased the Ca2+ crosslinking density in the gel structure. The morphological characteristics, the mechanical properties, and the non-cytotoxic behavior of the CNFT-alginate gels improved bioadhesion, growth, and proliferation of the cells onto the gels. Thus, the alginate-nanocellulose gels might find applications in tissue engineering field, as for instance, in tissue repair or wound healing applications. [ABSTRACT FROM AUTHOR]