Ultrasound assisted synthesis of nanosized oxide semiconductors/ordered mesoporous carbon nanoarchitectures

The present work reports the ultrasound assisted synthesis of nanosized oxide semiconductors, as TiO2 (anatase) and Bi2O3 (α-phase)/mesoporous carbon stable architectures exhibiting high photocatalytic activity for organic pollutants degradation.The use of ordered mesoporous carbon with a pore diameter around 5nm and high specific surface area of 1392m2/g was a successful one, providing an ideal support for semiconductor oxide photocatalysts. Thus, by using ultrasound assisted method the photoactive systems for organics removal from waste waters has been obtained.&nbsp;Due to the presence of the polar oxygenated groups on mesoporous carbon surface, these might stimulate the formation of the stable (nano) architectures, and enhance the interfacial combination of semiconducting oxide nanoparticles with carbon nanostructure. The prepared systems by this way have been characterized by N2-sorption measurements, X-ray diffraction, SEM microscopy and FTIR spectroscopy. A correlation between their structural, textural and morphological properties is related, and the photocatalytic activity of the synthesized materials has been checked for the methyl orange bleaching in liquid phase, under UV light.The photocatalytic performance of the synthesized nanosized oxide semiconductors/ordered mesoporous carbon nanoarchitectures was evaluated by bleacing of Methyl Orange (MO). It was found that the synthesized α-Bi2O3/mesoporous carbon and TiO2/mesoporous carbon composites showed a much higher degradation efficiencies (of 95% and 98%, respectively) as compared to commercial anatase nanoparticles. For the enhanced photocatalytic activity of the composite systems is responsible the synergistic effect as result of mesoporous carbon structure – oxide semiconductor interactions.</p

Electrospinning of Cyclodextrin–Oligolactide Derivatives

The materials used for the preparation of electrospun mats exhibit a large variety. Among them, cyclodextrins (CDs) and their derivatives have received thorough attention. Herein, we focus on the preparation of electrospun fibers based on biodegradable cyclodextrin–oligolactide (CDLA) derivatives, which may be qualified as polymer-free cyclodextrin. CDLA was prepared by ring opening of L-lactide initiated by the β-cyclodextrin. A clear structural image of the high-purity CDLA product was proved by MALDI MS. Preparation of the electrospun mats was optimized by taking into consideration the electrospinning parameters such as applied voltage, needle-to-collector distance, flow rate, the concentration of cyclodextrin solutions, and solvent type. The obtained electrospun fibers were morphologically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). SEM allowed the optimization of the electrospinning process to obtain beadless fibers with submicronic diameters. Further analysis by TEM and SAXS revealed the inner structural features of the CDLA-based filaments. Our results showed that the high purity CDLA materials, structurally well-defined at the molecular level, are suitable for the preparation of electrospun mats by using dimethylformamide or a water/acetonitrile mixture as electrospinning solvents, similar to lower molecular weight commercial cyclodextrin derivatives

Revealing the Effect of Synthesis Conditions on the Structural, Optical, and Antibacterial Properties of Cerium Oxide Nanoparticles

Cerium oxide nanoparticles were prepared by a precipitation method using Ce(IV) sulphate as precursor dispersed in glycerol with varying synthesis parameters such as temperature or precipitating agent. The structural and morphological characteristics of the obtained nanoparticles were investigated by X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy. The crystallite size of the nanoparticles varied between 13 and 17 nm. The presence of Ce3+ and Ce4+ was proved by XPS data in the CeO2 samples and the conservation of the fluorite structure was evinced by X-ray diffractograms with a contraction of the lattice parameter, regardless of the size of the nanoparticle. From diffuse reflectance spectra, two band gap energy values for the direct transition were observed. Depending on the synthesis condition, the red shift of gap energy and the blue shift of Urbach energy with increasing content of Ce3+ were ascertained. The antibacterial tests revealed that the cerium oxide nanoparticles show good antimicrobial activity towards the common pathogens Escherichia coli and Staphylococcus aureus

Electrospinning of Cyclodextrin&ndash;Oligolactide Derivatives

The materials used for the preparation of electrospun mats exhibit a large variety. Among them, cyclodextrins (CDs) and their derivatives have received thorough attention. Herein, we focus on the preparation of electrospun fibers based on biodegradable cyclodextrin&ndash;oligolactide (CDLA) derivatives, which may be qualified as polymer-free cyclodextrin. CDLA was prepared by ring opening of L-lactide initiated by the &beta;-cyclodextrin. A clear structural image of the high-purity CDLA product was proved by MALDI MS. Preparation of the electrospun mats was optimized by taking into consideration the electrospinning parameters such as applied voltage, needle-to-collector distance, flow rate, the concentration of cyclodextrin solutions, and solvent type. The obtained electrospun fibers were morphologically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). SEM allowed the optimization of the electrospinning process to obtain beadless fibers with submicronic diameters. Further analysis by TEM and SAXS revealed the inner structural features of the CDLA-based filaments. Our results showed that the high purity CDLA materials, structurally well-defined at the molecular level, are suitable for the preparation of electrospun mats by using dimethylformamide or a water/acetonitrile mixture as electrospinning solvents, similar to lower molecular weight commercial cyclodextrin derivatives

Synthesis, characterization and solution behaviour of oxidized pullulan

International audienceVarious amounts of carboxyl groups were introduced at C-6 of the non-ionic, water soluble polysaccharide, i.e. pullulan, by applying the well-established TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), sodium hypochlorite/sodium bromide oxidation protocol, varying the reaction time. The oxidized products, more water-soluble than pullulan, were further characterized by FT-IR, 1H NMR and 13C NMR techniques, in order to assess the degree of oxidation. The absolute molecular weight measurements performed using a multiangle laser light scattering molecular weight analyzer, reveals a sharp drop of the molecular weight of the samples oxidized for longer reaction times. The second virial coefficients (A2), increased from unoxidized pullulan to the oxidized samples. Dynamic light scattering (DLS) measurements provide zeta potentials and hydrodynamic radius for all studied samples. The viscosity of the initial and oxidized pullulan dilute aqueous solutions was studied in detail. All oxidized samples except the highest oxidized pullulan sample (OxPu8) showed strong polyelectrolyte behaviour, whereas this effect is less pronounced for OxPu8 due to the high degradation of the chains. The intrinsic viscosity and the interaction parameter were determined at 25 °C as a function of solvent ionic strength according to Wolf approach. The dependence of these parameters on the salt concentration follows Boltzmann sigmoid model