Thermoelectric properties of bulk multi-walled carbon nanotube - poly(vinylidene fluoride) nanocomposites: Study of the structure/property relationships

International audienceThe cross-plane thermoelectric properties of multi-walled carbon nanotubes-poly(vinylidene fluoride) (MWCNT-PVDF) nanocomposites were investigated at room temperature as a function of MWCNT content (from 5 to 50 wt%). Special attention was paid to the influence of the nature of the polymer crystal phase. Incorporation of MWCNT induces PVDF polar β-phase formation, coexisting with the major non polar α-phase. Significant improvement of the thermoelectric properties is evidenced, with the best values obtained at 50 wt% MWCNT loading. A post treatment at high temperature (T =165 °C) results in the development of the polar γ-phase from the α- and β-polymorphs. Nanocomposites annealing significantly enhances the Seebeck coefficient, typically from 14 up to 20 μV K−1, yielding a power factor of 4.6 × 10−2 μW m−1 K−2 and a figure of merit ZT of 1.6 × 10−5 at 50 wt%, which is the best ZT value that can be found in the literature, regarding MWCNT-PVDF bulk nanocomposites. Structural analysis underlines for the first time the impact of the polymer polar γ-phase on the nanocomposite thermoelectric properties

Relations entre structure et propriétés physiques macroscopiques de copolymères P(VDF-co-TrFE)

International audienc

ON THE BRITTLE-TO-DUCTILE TRANSITION OF PLA : INFLUENCE OF MACROMOLECULAR ORIENTATION

International audienc

Substitution degree and fatty chain length influence on structure and properties of fatty acid cellulose esters

International audienceA series of fatty acid cellulose esters (FACEs) with both various degrees of substitution (from DS = 1.7 to 3) and side chain length were obtained by grafting aliphatic acid chlorides (from C10 to C16) onto cellulose backbone, in a homogeneous LiCl/DMAc medium. These materials were characterized by Fourier Transformed InfraRed (FTIR) and Nuclear Magnetic Resonance of Proton (1H NMR) spectroscopies, as well as Wide Angle X-ray Scattering (WAXS), Differential Scanning Calorimetry (DSC), mechanical analyses and chemical resistance to concentrated acid and alkali solutions. Whatever the alkyl chains length and the DS, all samples displayed a layered structure composed of a planar arrangement of parallel cellulosic backbones with fully extended flexible side chains oriented perpendicular to the planar structure without interdigitation. The alkyl chains were able to crystallize as soon as they are long enough. As the DS decreased, the plasticizing effect of the alkyl chains was less pronounced and their ability to crystallize was improved. Regarding the mechanical behavior and the chemical resistance, similar results were observed whatever the DS is

Etudes comparatives de différents copolymères piézoélectriques fluorés

National audienc

Colorimetric sensing of dopamine in beef meat using copper sulfide encapsulated within bovine serum albumin functionalized with copper phosphate (CuS-BSA-Cu₃(PO₄)₂) nanoparticles

International audienceA novel nanosensor with peroxidase enzyme-mimetic activity, based on CuS-BSA-Cu3(PO4)2 nanoparticles, was developed. CuS-BSA nanoparticles were first synthesized using a facile bio-mineralization assay. Conjugation of Cu3(PO4)2 with CuS-BSA generates CuS-BSA-Cu3(PO4)2 nanoparticles (NPs) of 10 nm in size with high catalytic activity against a peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB). The catalytic action was based on a remarkable color change from colorless TMB into blue oxidized product (oxTMB) with absorption maximum at 654 nm. The enzyme-mimetic activity of CuS-BSA-Cu3(PO4)2 nanoparticles was believed to occur through hydroxyl radical (HOradical dot) generation in presence of H2O2, which was inhibited upon addition of dopamine. Increasing concentrations of dopamine induced a gradual decrease of the nanoparticles' catalytic activity. The developed colorimetric sensor displayed a limit of detection of 0.13 µM for dopamine over 0.05-100 µM linear range and high specificity. The performance of the nanosensor for sensing dopamine in beef meat and blood samples was evaluated and proved to be promising for diagnostic applications without the requirement of complex and expensive instrumentation

Relations entre la structure et les propriétés de composites piézoélectriques de BTO/P(VDF-co-TrFE)

National audienc

Ultrasmall CuS-BSA-Cu3(PO4)2 nanozyme for highly efficient colorimetric sensing of H2O2 and glucose in contact lens care solutions and human serum

International audienceThis work reports on the synthesis of organic-inorganic hybrid nanoscale materials, CuS-BSA-Cu3(PO4)2. The developed nanoparticles were characterized by various techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectrophotometry, Fourier transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS). The CuS-BSA-Cu3(PO4)2 were successfully applied as artificial colorimetric probes in sensing H2O2, the final outcome of glucose oxidation, and proved to be efficient peroxidase mimics for the catalytic conversion of a chromogenic substrate, 3,3′,5,5′-tetramethylbenzidine (TMB), into a blue colored oxidized product (oxTMB) which can be easily visualized by the naked eye and monitored by a great absorption peak at 654 nm in the UV–vis spectrophotometry. A highly efficient, rapid, sensitive, and selective determination of H2O2 and glucose have been achieved with very low detection limits of 22 nM, and 27.6 nM over 0–8 μM and 0–1000 μM linear ranges, respectively. Compared to CuS-BSA, CuS-BSA-Cu3(PO4)2 exhibited improved peroxidase-like catalytic activity. Based on these observations, the performance of this approach was successfully validated in contact lens care solutions and human serum samples