Single-crystalline nanowires of SiC synthesized by carbothermal reduction of electrospun PVP/TEOS composite fibres

Nanowires of SiC were synthesized by carbothermally reducing PVP/TEOS composite fibres obtained by electrospinning. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) indicated that the SiC nanowires are single crystalline in nature. Both Fourier-transformed infrared spectroscopy and HRTEM indicated that a thin layer of SiO2 was formed on the outer surface of the nanowire as a result of post-heat treatment for the removal of residual carbon. Such SiO2 layer protects the inner SiC fibre from further oxidation. The formation mechanism of single-crystalline SiC nanowires was proposed based on our understanding and characterizations. The growth of the nanowire is believed to be along the ( 111) of its cubic cell.

Synthesis and properties of a novel isomeric polyimide/SiO2 hybrid material

A novel isomeric polyimide/SiO2 hybrid material was successfully prepared through sol-gel technique, and its structure, thermal properties and nano-indenter properties were investigated. First, 3-[(4-phenylethynyl)phthalimide]propyl triethoxysilane (PEIPTES) was successfully synthesized, its structure was characterized by elemental analysis, FT-IR and C-13 NMR. The researches on solubility and thermal properties of PEIPTES show that it can be used for modifying nano-SiO2 precursor. Nano-SiO2 precursor was synthesized by tetraethoxysilane (TECS) through sol-gel technique. Then the PEIPTES solution and the nano-SiO2 precursor were mixed for 6 h to let the PEIPTES molecules react with the nano-SiO2 precursor, and modified nano-SiO2 precursor was obtained. The modified reaction was confirmed by the analyses of FT-IR. At last, isomeric polyimide/SiO2 hybrid material was produced by using isomeric polyimide resin solution and the modified nano-SiO2 precursor after heat treatment process. The structure analysis by SEM indicated that SiO2 particles dispersed in isomeric polyimide matrix homogeneously with nanoscale. Thermogravimetric analyzer, dynamic mechanical thermal analyzer and nano-indenter XP was employed to detect the properties of the materials, the results demonstrated that isomeric polyimide/SiO2 hybrid material has much better thermal properties and nano-indenter properties than those of isomeric polyimide.

Hydrothermal synthesis of ZrW2O8 nanorods

Negative thermal expansion ZrW2O8 nanorods were synthesized by a rapid low-temperature hydrothermal route, followed with a heat treatment at 500 degrees C for 6h. Acidity of the HCl addition to the mixed solution in the hydrothermal condition strongly affects the formation of the precursor ZrW2O7(OH)(2)(H2O)(2). High acidity of HCl in the range of 5-10 N facilitates the nucleation of ZrW2O7(OH)(2)(H2O)(2), but constrains its growth. Low acidity of HCl addition (< 5 N) only obtained the products ZrO2 and WO3 by firing the precursors. FE-SEM images revealed that the shape and size of ZrW2O8 were modeled after its precursor ZrW2O7(OH)(2)(H2O)(2).

Synthesis and characterization of SiO2/Gd2O3 : Eu core-shell luminescent materials

Europium-doped Gd2O3 with an average size of similar to15 nm was coated on the surface of preformed silica nanospheres by the wet chemical method. SEM and TEM photographs showed that SiO2/Gd2O3:Eu core-shell submicrospheres are obtained. XRD patterns indicated that the Gd2O3:Eu shell is crystalline after heat treatment. FTIR and XPS spectra showed that the Gd2O3:Eu shell is linked to the silica surface by forming a Si-O-Gd bond. Photoluminescence studies showed that the luminescent properties are still retained after coating on an inert silica core; additionally, we noted that the emitting peaks are broadened, which results from size effects and interface effects of nanocrystal.

Comparative study on the photoluminescent properties of siliceous MCM-41 with silica particles and xerogels

The samples of as-synthesized siliceous MCM-41, extracted MCM-41, amorphous silica particles and silica xerogels were heat treated from room temperature to 1000degreesC. Their photoluminescence (PL) spectra at room temperature excited by 254nm and 365nm ultraviolet light (UV) were investigated and compared. Excited by 254nm UV the MCM-41 samples do not display PL but amorphous silica particles and silica xerogels show PL, which changes with the heat treatment conditions for the samples. However, when excited by 365nm UV the PL spectra for the MCM-41 and the amorphous samples are similar. The carbon impurity and E' center mechanisms can be ruled out as the origin of PL in siliceous MCM-41 under UV excitation. The PL of MCM-41 series samples probably originates from oxygen-related defect center like dropSi-O-. according to the present work.

In situ synthesis and characterization of multiwalled carbon nanotube/Au nanoparticle composite materials

An effective and facile in Situ reduction approach for the fabrication of carbon nanotube-supported Au nanoparticle (CNT/Au NP) composite nanomaterials is demonstrated in this article. Linear polyethyleneimine (PEI) is ingeniously used as both a functionalizing agent for the multiwalled carbon nanotubes (MWNTs) and a reducing agent for the formation of An NPs. This method involves a simple mixing process followed by a mild heating process. This approach does not need the exhaustive surface oxidation process of CNTs. The coverage of Au NPs on CNTs is tunable by varying the experimental parameters, such as the initial molar ratio of PEI to HAuCl4, the relative concentration of PEI and HAUCl(4) to MWNTs, and the temperature and duration of the heat treatment. More importantly, even the heterogeneous CNT/Au composite nanowires are obtainable through this method. TEM, XPS, and XRD are all used to characterize the CNT/Au composite materials. In addition, the optical and electrocatalytic properties are investigated.

Conformational changes of beta-lactoglobulin induced by anionic phospholipid

Conformational changes of beta-lactoglobulin (beta-LG) induced by anionic phospholipid (dimyristoylphosphatidylglycerol, DMPG) at physiological conditions (pH 7.0) have been investigated by UV-VIS, circular dichroism (CD) and fluorescence spectra. The experimental results suggest that beta-LG-DMPG interactions cause beta-LG a structural reorganization of the secondary structure elements accompanied by an increase in alpha-helical content, and a loosening of the protein tertiary structure. The interaction forces between beta-LG and DMPG are further evaluated by fluorescence spectra. The fluorescence spectral data show that conformational changes in the protein are driven by electrostatic interaction at first, then by hydrophobic interaction between a protein with a negative net charge and a negatively charged phospholipid.