Hydrothermal synthesis and characterization of monodisperse α-Fe2O3 nanoparticles

Monodisperse α-Fe₂O₃ nanoparticles have been successfully prepared by hydrothermal synthetic route using FeCl₃, CH₃COONa as reagents and reacted at 200 °C for 12 h. The morphology and structure of products were characterized by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the α-Fe₂O₃ nanoparticles were single-crystalline hexagonal structure and average diameters were about 80 nm. Magnetic properties have been detected by a vibrating sample magnetometer at room temperature. The nanoparticles exhibited a ferromagnetic behavior with the coercive force (Hc), saturation magnetization (Ms) and remanent magnetization (Mr) was 185.28 Oe and 0.494 emu/g, 0.077 emu/g.     

Characterisation of blends between poly(ε-caprolactone) and polysaccharides for tissue engineering applications

In this work, bioartificial binary blends between poly(ε-caprolactone) (PCL) and a polysaccharide (chitosan (CS) or starch (S)) with different contents of the natural polymer (5–30 wt.%) were produced. Melt-mixing and double-precipitation were the methods used for the obtainment of PCL/S and PCL/CS blends, respectively. Tubular scaffolds were produced from bioartificial blends by melt-extrusion. Physico-chemical characterisation was performed by differential scanning calorimetry analysis (DSC), thermogravimetry (TGA), scanning electron microscopy (SEM), infrared analysis (FTIR-ATR and micro-ATR mapping), atomic force microscopy (AFM) and stress–strain tests. Blends were not miscible, phase-separated systems, showing a homogeneous composition and morphology only at low polysaccharide content (≤ 10 wt.%). The biocompatibility of bioartificial guides was investigated by culturing NIH-3T3 mouse fibroblasts. Cells response showed the following order: PCL/S > PCL > PCL/CS. For each blend type, biocompatibility increased with decreasing the polysaccharide content. In vitro cell tests using S5Y5 neuroblastoma cells, carried out on the most biocompatible blends, assessed their absence of cytotoxicity towards these model cells of the nervous tissue. Results showed that blends with a low chitosan or starch content (≤ 10 wt.%) are promising for the regeneration of tissues requiring tubular scaffolds, such as the peripheral nerves.     

Optoelectronic properties of β-Fe2O3 hollow nanoparticles

The effect of hollow structure on the optoelectronic properties of β-Fe₂O₃ hollow nanoparticles (HNPs) was determined. Spectrophotometry showed that the optical transmittance of the β-Fe₂O₃ HNPs was less than 40% in the visible-light region. This opaqueness was suggested to be an optical characteristic, commonly found in the authors' previous studies of TiO₂ and δ-Al₂O₃ HNPs. In addition, β-Fe₂O₃ HNPs had a band gap (1.86 eV) between amorphous (1.73 eV) and polycrystalline (1.97 eV) β-Fe₂O₃ thin films, which was a 5–7 nm thick shell that embraced an intermediate volume of the crystal phase, in-between the two thin films.     

Synthesis and characterization of a novel poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl-CdS nanocomposites through chemical hybridization

A novel bi-functional photorefractive (PR) poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl with carbazolyl fragments and chromophoric azophenyl was synthesized by a post azo coupling reaction and characterized by ¹H NMR, elemental analysis, UV–Vis absorption and FTIR spectroscopy. Then chemical hybridized poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl-CdS nanocomposites with different molar ratio of CdS to poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl were prepared. It was confirmed that the CdS particles had a nanoscale size and quantum confinement effect adopting transmission electron microscopy and UV–Vis absorption spectroscopy. The generation of photocurrent on illumination and photoconductive properties of the nanocomposites were studied. Significant enhancement in photoconductivity induced by the chemical doping of CdS in poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl has also been demonstrated.     

Study of autoabsorption for total α and β counting

The RaMsEs Group (Radioprotection et Mesures Environnementales) of the IPHC performs research and offers services mainly in the field of radioactivity measurements and sample analysis. This report will describe some of our recent experience using a semiautomatic evaporation system to prepare large area thin deposits for total α and β counting and gives experimental and simulated results for the autoabsorption coefficients.     

Optical property of poly(9,9-dioctylfluorene) gel with β phase and application to polymer light emitting diode

Poly (9,9-dioctylfluorene)(F8) gel with β phase has been investigated in terms of optical absorption, photoluminescence measurements and Fourier transform infrared spectroscopy. The optical properties of the F8 gel markedly changed in the temperature range from 70 to 80 °C owing to the vibration of polymer chain related to the glass transition temperature of F8. F8 films by thermal printing method had the characteristic particulate morphology. Current efficiencies of polymer light emitting diodes (PLEDs) with the β phase of F8 fabricated by the thermal printing method were better than that with the amorphous phase of F8 by the spin-coating method. We demonstrate the β phase effects of PLEDs characteristics by the thermal printing method.     

Relationship between soil bulk density and PVR of in situ γ spectra

This paper presents the specific relationship between soil bulk density and peak-to-valley ratio (PVR) of natural radionuclides in in situ γ spectra, by theoretical deduction, Monte Carlo simulation and experimental research. Results show that for an infinite half-space volume source, PVR is a constant independent of the diverse soil bulk density. But for a limited-scale volume source, PVR would decrease slowly with an increase in soil bulk density, and the smaller the source scale, the larger the PVR variation with soil bulk density. However, the PVR variation with bulk density is very small in general. For field measurements, the volume source thickness is uncontrollable in practice, and the volume source radius should not be as small as needed for the limitation of low detection efficiency. Hence the soil bulk density could not be determined through the information from PVR of field in situ γ spectra.     

Effects of hydrolysis on dodecyl alcohol modified β-CaSiO3 particles and PDLLA/modified β-CaSiO3 composite films

In this research, β-CaSiO₃ particles were surface modified with dodecyl alcohol, and Poly-(DL-lactic acid) (PDLLA)/modified β-CaSiO₃ composite films were fabricated with a homogenous dispersion of β-CaSiO₃ particles in the PDLLA matrix. The aim of the study was to investigate the properties of the composite films before and after hydrolytic treatment. SEM images showed retained homogenous dispersion of β-CaSiO₃ particles after hydrolysis and tensile test also showed maintained mechanical property. Simulated body fluid (SBF) incubation experiment suggested that hydrolytic treatment did not affect the formation of hydroxyapatite on the surface of the composite films. The hydrophilicity of the composites was greatly recovered (from 69.82° to 50.28°) after hydrolysis. In addition, cells cultured on composite films after hydrolysis presented the highest cell proliferation rate and differentiation level. All of these results suggested that the surface modification of silicate particles with dodecyl alcohol along with reversible hydrolytic treatment was an effective and feasible approach to fabricate polymer/silicate composite materials with improved properties.     

Effect of Ni-modified α-Al2O3 prepared by sol–gel and solvothermal methods on the characteristics and catalytic properties of Pd/α-Al2O3 catalysts

In the present study, Ni-modified α-Al₂O₃ with Ni/Al ratios of 0.3 and 0.5 were prepared by sol–gel and solvothermal method and then were impregnated with 0.3 wt.% Pd. Due to different crystallization mechanism of the two preparation methods used, addition of nickel during preparation of α-Al₂O₃ resulted in various species such as NiAl₂O₄, mixed phases between NiAl₂O₄ and α-Al₂O₃, and mixed phases between NiAl₂O₄ and NiO. As revealed by NH₃-temperature programmed desorption, formation of NiAl₂O₄ drastically reduced acidity of alumina, hence lower amounts of coke deposited during acetylene hydrogenation was found for the Ni-modified α-Al₂O₃ supported catalysts. For any given method, ethylene selectivity was improved in the order of Pd/Ni–Al₂O₃-0.5 > Pd/Ni–Al₂O₃-0.3 > Pd/Ni–Al₂O₃-0  Pd/α–Al₂O₃-commercial. When comparing the samples prepared by different techniques, the sol–gel-made samples showed better performances than the solvothermal-derived ones.     

A variationally consistent αFEM (VCαFEM) for solution bounds and nearly exact solution to solid mechanics problems using quadrilateral elements

A variationally consistent alpha finite element method (VC αFEM) for quadrilateral isoparametric elements is presented by constructing an assumed strain field in which the gradient of the compatible strain field is scaled with a free parameter α. The assumed strain field satisfies the orthogonal condition and the Hellinger–Reissner variational principle is used to establish the discretized system of equations. It is shown that the strain energy is a second‐order continuous function of α, and the VC αFEM can produce both lower and upper bounds to the exact solution in the strain energy for all elasticity problems by choosing a proper α∈[0, α_upper]. Based on this bound property, an exact‐α approach has been devised to give an ultra‐accurate solution that is very close to the exact one in the strain energy. Furthermore, the exact‐α approach also works well for volumetric locking problems, by simply replacing the strain gradient matrix by a stabilization matrix. In addition, a regularization‐α approach has also been suggested to overcome possible hourglass instability. Intensive numerical studies have been conducted to confirm the properties of the present VC αFEM, and a very good performance has been found in comparing to a large number of existing FEM models. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of optical properties of TiO2 nanoparticles and PAN/TiO2 composite nanofibers

The aim of the study was the production of thin composite nanofibrous mats PAN/TiO₂ nanoparticles using the electrospinning method from solution of PAN/TiO2/DMF. TiO₂ nanoparticles were obtained using sol-gel method. To prepare sol mixture, organic alkoxides precursor of titanium isopropoxide and water solution were used. Calcination of TiO-gel and following milling were carried out to obtain nanoparticles of TiO₂ rutile phase. In order to analyze the structure of the obtained particles, we used X-ray diffraction analysis (XRD) and energy dispersive spectrometer (EDS). Analysis of the morphology and chemical composition of the resulting composite nanofibers were carried out using a scanning electron microscope (SEM) with EDS. The analysis of the optical properties and the energy band structure prepared nanoparticles and thin composite nanofibrous mats were determined by spectral analysis of the absorbance as a function of the energy of radiation obtained using a UV–Vis spectrophotometer.     

Facile Synthesis of γ‐In2Se3 Nanoflowers toward High Performance Self‐Powered Broadband γ‐In2Se3/Si Heterojunction Photodiode

An effective colloidal process involving the hot‐injection method is developed to synthesize uniform nanoflowers consisting of 2D γ‐In₂Se₃ nanosheets. By exploiting the narrow direct bandgap and high absorption coefficient in the visible light range of In₂Se₃, a high‐quality γ‐In₂Se₃/Si heterojunction photodiode is fabricated. This photodiode shows a high photoresponse under light illumination, short response/recovery times, and long‐term durability. In addition, the γ‐In₂Se₃/Si heterojunction photodiode is self‐powered and displays a broadband spectral response ranging from UV to IR with a high responsivity and detectivity. These excellent performances make the γ‐In₂Se₃/Si heterojunction very interesting as highly efficient photodetectors.     

High temperature creep of a hot-pressed β-sialon

The four-point bending creep properties of a hot-pressed β-sialon with Sm–melilite solid solution (denoted as M′) as intergranular phase have been studied in the temperature range 1250–1350°C in air. Creep rates plotted against stresses gave stress exponents of 1.45, 1.51 and 1.72 at 1250, 1300 and 1350°C, respectively, and Arrhenius plot between creep rate and temperature yielded a creep activation energy of 576 kJ mol⁻¹. Cavities were found to be mainly on the triple grain junctions. Diffusion coupled with grain boundary sliding and accompanied by the formation of wedge-shaped cavities was identified as the dominant creep mechanism.     

Efficient and Durable Vaccine against Intimin β of Diarrheagenic E. Coli Induced by Clay Nanoparticles

Improved strategies are urgently required to control infections with enterohemorrhagic Escherichia coli and enteropathogenic E. coli, two dominant zoonotic enteric pathogens responsible for a wide spectrum of illnesses as well as deaths of human being, with tremendous financial cost worldwide. The present study investigates the capacity of two clay nanoparticles (NPs) with opposite surface charges, namely synthetic layered double hydroxide (LDH) and hectorite (HEC) NPs as adjuvants to promote strong immune responses against the infections. Here both LDH and HEC NPs are showed to be able to carry an appreciable amount of Intimin β (1.1 and 4.4 mg per mg clay nanomaterials, respectively) and significantly facilitate antigen uptake by antigen‐presenting cells. Remarkably, these clay NPs induce strong antibody and cell‐mediated immune responses, which are much higher than that by the potent adjuvant, QuilA. Furthermore, these strong immune responses are well maintained for at least four months in the mouse model, during which there are no changes in histopathology of the animal organs. Collectively these data demonstrate the suitability of LDH and HEC NPs as useful adjuvants in new‐generation vaccine formulations to control various infectious diseases.     

Physico/chemical characterization and preliminary human histology assessment of a β-TCP particulate material for bone augmentation

This study aimed to physico/chemically characterize and evaluate the in vivo performance of a β-TCP particulate grafting material. SEM/TEM, and EDS and XPS were used for morphology and chemistry assessment, respectively. FTIR was used to determine Ca–P phases characteristic bands. Rietveld refinement/XRD spectra was performed for secondary phase detection. Particle size distribution and specific surface were assessed by a scattering-laser based technique and BET, respectively. Mercury porosimetry was employed to determine pore-size distribution. For in vivo evaluation, the grafting material was used in 12 patients' sinus lifts, and biopsies were obtained at post-operative times of 3, 6, and 9 months. SEM/TEM revealed multigrained particles with interconnected pores. EDS showed Ca, P, and O, with stoichiometry close to theoretical values. XRD/Rietveld showed that the material presented crystalline β-TCP with ~ 9% β-Ca₂P₂O₇ secondary phase. FTIR did not detect the presence of bands related to α-TCP. Human histologic assessment showed that newly formed bone was present at 3 months, and degrees of bone organization increased as time elapsed in vivo. Human histology showed that the material is suitable for bone regeneration in a maxillofacial complex region.