Bismuth Nanoparticles Supported on Biobased Chitosan as Sustainable Catalysts for the Selective Hydrogenation of Nitroarenes

International audienceThe use of chitosan as a support in the field of catalysis has gained tremendous interest because of its abundance and sustainability. We herein disclose a straightforward strategy to trap and stabilize bismuth nanoparticles (BiNPs) on chitosan biopolymer Bi@CS and their use for catalytic applications. Bi@CS was configured as micrometer-thick films, porous beads, and native powders analyzed and next used for the controlled and selective reduction of nitroaromatic compounds to their corresponding anilines and azoarenes, respectively, by varying the concentration medium in reducing NaBH 4. A regioselective mechanism has been suggested. Powder nanocomposites CSp-BiNPs exhibited high catalytic capacity, and 10 corresponding anilines and 15 azoarenes were obtained with very high yields. The reductions were achieved under mild and sustainable reaction conditions (water solvent and room temperature) with easy processing and 12 recovery cycles. Shaped catalysts were easily recovered by simple filtration. This catalyst, derived from nontoxic and affordable bismuth metal supported on chitosan ocean waste, presents significant improvements in the realm of sustainable chemistry and could open a new channel of possibilities for green catalysis

Exploiting poly(ε-caprolactone) grafted from hydrohydroxymethylated sunflower oil as biodegradable coating material of water-soluble fertilizers

International audienceIn the present study, hyperbranched poly(ε-caprolactones) were prepared and used as coating materials to prepare slow release diammonium phosphate (DAP) fertilizer. Firstly, the sunflower oil was hydrohydroxymethylated by one-pot two-step process using Rh(acac)(CO)2 as catalyst, and triethylamine as ligand. Next, the bio-based hyperbranched poly(ɛ-caprolactone) (PCL) were prepared in open air by in-situ ring-opening polymerization of ε-caprolactone using hydrohydroxymethylated sunflower oil as macro-initiator and tetra(phenylethynyl)tin (Sn(C ≡ CPh)4) as catalyst. The structures of the prepared polymers (SFO-O-g-PCL) were confirmed by nuclear magnetic resonance (1H NMR) and the infrared spectroscopy (FTIR). Furthermore, molecular weight values around 20.000 g.mol−1 of PCL grafted in SFO-O-g-PCL were obtained, the thermal stability and morphology of the coated film were also evaluated using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) respectively. The hydrophobic character of the films prepared from SFO-O-g-PCL was confirmed by measuring the contact angle of water droplets. In the second part, the DAP granular fertilizers were uniformly coated by the prepared material (SFO-O-g-PCL) using a laboratory rotary drum. Then the slow release performance in water of the coated and uncoated DAP fertilizer granules was evaluated by tracking the cumulative concentration of P2O5 released. Thus, it was found that only 10 % of P2O5 was released after 2 h of essay from the coated DAP compared to a total release of P2O5 from uncoated DAP (conventional fertilizer) during the same period. This finding opens a wide perspective to combine the advantages of hydrophobic polyesters and bio-based oils to produce biodegradable coating agents

Synthesis and antibacterial behavior of bio-composite materials-based on poly(ε-caprolactone)/bentonite

Several clay minerals as inorganic fillers were incorporated to aliphatic polyester by various procedures. The target of enhancing the physicochemical properties of the resulting composite material leading thereby to overcome the limitations of neat polyesters. Still, bentonite (Bnt) as a clay mineral has been relatively unexplored as a reinforcing agent of the poly(ε-caprolactone) (PCL). In this study, a bio-nanocomposite based on poly (ε-caprolactone) & bentonite nanofiller was prepared by in-situ ring opening polymerization (ROP) of ε-caprolactone (ε-CL) under open air using tin-based catalyst. The obtained bio-composites (PCL-OBnt) were fully characterized to examine their structural interactions, thermal stability, mechanical, and morphological properties. Finally, the antimicrobial activity against S. epidermidis and S. aureus of the prepared bio-composites materials was evaluated

Implementation and Characterization of a Laminate Hybrid Composite Based on Palm Tree and Glass Fibers

In this work, laminated polyester thermoset composites based on palm tree fibers extracted from palms leaflets and glass mats fibers were manufactured to develop hybrid compositions with good mechanical properties; the mixture of fibers was elaborated to not exceed 25 vol.%. Samples were prepared with a resin transfer molding (RTM) method and mechanically characterized using tensile and flexural, hardness, and impact tests, and ultrasonic waves as a non-destructive technique. The water sorption of these composite materials was carried out in addition to solar irradiation aging for approximately 300 days to predict the applicability and the long-term performance of the manufactured composites. Results have shown that the use of glass fibers significantly increased all properties; however, an optimum combination of the mixture could be interesting and could be developed with less glass sheet and more natural fibers, which is the goal of this study. On the other hand, exposure to natural sunlight deteriorated the mechanical resistance of the neat resin after only 60 days, while the composites kept high mechanical resistance for 365 days of exposure

Gravure par contact du silicium à l’aide d’électrodes en or nanoporeux

National audienc

Preuve de concept de texturisation de surface de Silicium par MACE pour des applications photovoltaïques

National audienc

3D patterning of silicon by contact etching with anodically biased nanoporous gold electrodes

A novel strategy to achieve 3D pattern transfer into silicon in a single step without using lithography is presented. Etching is performed electrochemically in HF media by contacting silicon with a positively biased, patterned, metal electrode. Dissolution is localized at the Si/metal contacts and patterning is obtained as the electrode digs into the substrate. Previous attempts at imprinting Si using bulk metal electrodes have been limited by electrolyte blockage. Here, the problem is solved by using, for the first time, a nanoporous metal electrode that allows the electrolyte to access the entire Si/metal interface, irrespective of the electrode dimensions. As a proof of concept, imprinting of well-defined arrays of inverted pyramids has been performed with sub-micrometer spatial resolution over 1 mm2 using a nanoporous gold electrode of the complementary shape. Under a polarization of +0.3 V/SME in 5 M HF, the etch rate is ~0.5 μm min−1. The pyramidal pattern is imprinted independently of the Si crystallographic orientation. This maskless imprinting technique opens new opportunities in the fabrication of Si microstructures. Keywords: Silicon, Nanoporous gold, Imprinting, Microstructure, MAC

A flexible self-poled piezocomposite nanogenerator based on H₂(Zr_0.1Ti_0.9)₃O₇ nanowires and polylactic acid biopolymer

The field of piezoelectric nanogenerators is rapidly growing as a promising technology for driving lowpower portable devices and self-powered electronic systems by converting wasted mechanical energy into electric energy. In this study, we designed a flexible and self-poled piezocomposite nanogenerator based on lead-free H 2 (Zr 0.1 Ti 0.9) 3 O 7 (HZTO) nanowires and a polylactic acid (PLA) biodegradable polymer. By using a piezoresponse force microscope (PFM), the piezoelectric coefficient (d 33) of a single HZTO nanowire was found to be 26 pm V À1. The piezoelectric energy harvesting performances of a selfpoled piezocomposite film fabricated by embedding core-shell structured HZTO nanowires by polydopamine into the PLA matrix were tested. The piezoelectric nanogenerator demonstrated enhanced output performances (an open-circuit voltage of 5.41 V, short-circuit current of 0.26 mA and maximum power density of 463.5 mW cm À3 at a low resistive load of 2.5 MU). Besides, the developed device can charge different capacitors by regular mechanical impartations and can power a red lightemitting LED diode by various biomechanical motions. This study reveals the benefits of combining HZTO nanowires and PLA biopolymer in designing high-performance piezoelectric nanocomposites for biomechanical energy harvesting