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.

A new blue phosphorescent glass-ceramic: Rare-earth-doped calcium aluminoborate

A new blue phosphorescent glass-ceramic, Eu2+ and Nd3+, co-doped CaO-Al2O3-B2O3, was synthesized. After the irradiation with ultraviolet (UV) light, the glass-ceramic emitted blue long-lasting phosphorescence (LLP) with a spectrum peaking at about 464 nm ascribed to the characteristic 4f(6)5d(1) -> 8S(7/2) transition of Eu2+. This phosphorescence can be seen in the dark 1 h after the irradiation. However, the transparent Eu2+ and Nd3+ co-doped CaO-Al2O3-B2O3 glass did not show the phosphorescence. By the X-ray diffraction diffusion (XRD) data, alpha-CaAl2B2O7 was demonstrated to be the crystallites in the glass-ceramic. We think that alpha-CaAl2B2O7:Eu2+ Nd3+ crystallites produced during the heat treatment of the glass contribute to the LLP of the glass-ceramic.

Thermoluminescence studies of rare earth doped Sr2Mg(BO3)(2) phosphor

The Sr2Mg(BO3)(2) phosphors doped respectively with Tm3+, Tb3+ and Dy3+ as activator were prepared by high temperature solid-state reaction. All the thermo luminescence curves of the phosphors consisted of two isolated peaks and the Dy3+ activated sample exhibited the strongest thermo luminescence intensity. The kinetic parameters of the thermoluminescence of Sr2Mg(BO3)(2):0.04 Dy were calculated employing the peak shape method and 3 dimensional thermo luminescent emission spectra were observed peaking at 480, 579, 662 and 755 nm due to the characteristic transition of Dy3+. In addition, the pre-irradiation heat-treatment and the thermoluminescence dose response of Sr2Mg(BO3)(2):0.04 Dy were investigated.

Patterning and luminescent properties of nanocrystallineY(2)O(3): Eu3+ phosphor films by sol-gel soft lithography

Nanocrystalline Y2O3:Eu3+ phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained, which mainly consisted of grains with an average size of 70 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped Eu3+ showed its characteristic emission in crystalline Y2O3 phosphor films due to an efficient energy transfer from Y2O3 host to them. Both the lifetimes and PL intensity of the Eu3+ increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+ were determined to be 5 mol%.

Preparation, patterning and luminescent properties of nanocrystalline Gd2O3 : A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films via Pechini sol-gel soft lithography

Nanocrystalline Gd2O3:A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and that the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained by optimizing the composition of the coating sol, which mainly consisted of grains with an average size of 70 nm and a thickness of 550 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline Gd2O3 phosphor films due to an efficient energy transfer from Gd2O3 host to them. Both the lifetimes and PL intensity of the rare earth ions increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+, Dy3+, sm(3+), Er3+ were determined to be 5, 0.25, 1 and 1.5 mol% of Gd3+ in Gd2O3 films, respectively.

Patterning and optical properties rhodamine B-doped organic-inorganic silica films fabricated by sol-gel soft lithography

Rhodamine B (RB)-doped organic-inorganic silica films and their patterning were fabricated by a sol-gel process combined with a soft lithography. The resulted film samples were characterized by atomic force microscope (AFM), optical microscope and UV/Vis absorption and photoluminescence excitation and emission spectra. The effects of the concentration of the RB dye and heat treatment temperature on the optical properties of the hybrid silica films have been studied. Four kinds of patterning structures with film line widths of 5, 10, 20 and 50 mum have been obtained by micromolding in capillaries by a soft lithography technique. The RB-doped hybrid silica films present a red color, with an excitation and emission bands around 564 and 585 mum, respectively. With increasing the RB concentration, the emission intensity of the RB-doped hybrid silica films increases and the emission maximum presents a red shift. The emission intensity of the films decreases with increasing the heat treatment temperatures.

Mechanism of phase transformation and formation of barium hexaferrite doped with rare-earths in sol-gel process

The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La3+ Were studied by chemical phase analysis, X-ray diffraction and infrared spectrometry analysis. The experimental results show that phase transformation reactions of FeCO3, Fe2O3 and BaFe2O4, barium hexaferrite and gamma-Fe2O3 take place in the heat treatment of gel. While the doping lanthanide ion replace barium ion, an equivalent quantity of Fe3+ are reduced to Fe2+ to maintain the charge equilibrium.

Methanol tolerant FeTPP-Pt/C Co-catalysts for the electroreduction of oxygen

It was found for the first time that iron tetraphenylporphyrin (FeTPP)-Pt/C showed the good activity for the electroreduction of oxygen and methanol tolerant ability. Their performances were related to the heat-treatment temperature.

Sol-gel derived silicate oxyapatite phosphor films doped with rare earth ions

Rare-earth (Eu3+, Tb3+)-doped Ca2Y8(SiO4)(6)O-2 luminescent thin films were dip-coated on silicon and quartz glass substrates through a sol-gel route. X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resultant films. The results of XRD reveal that these films remain amorphous below 700 degreesC, begin to crystallize at 800 degreesC, and crystallize completely around 1000 degreesC with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM micrographs, where particles with various shape and average size of 250 nm can be resolved. The Eu3+ and Tb3+ ions show their characteristic red (D-5(0)-F-7(2)) and green (D-5(4)-F-7(5)) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime of Eu-3divided by increases with the heat treatment temperature front 700 to 1100 degreesC.

Multi-color long-lasting phosphorescence in Mn2+-doped ZnO-B2O3-SiO2 glass-ceramics

Multi-color LLP phenomenon was observed in Mn2+-doped ZnO-B2O3-SiO2 glassceramics after the irradiation of a UV lamp at room temperature. Transparent ZnO-B2O3-SiO2 glass emitted reddish LLP while opaque glass-ceramics prepared by the glass sample after heat treatment emitted yellowish or greenish LLP. The change of the phosphorescence is due to the alteration of co-ordination state of Mn2+. The phosphorescence of the samples was seen in the dark with naked eyes even 12 h after the irradiation with a UV lamp (lambda(max) = 254 nm) for 30 min. Based on the approximative t(-1) decay law of the phosphorescence, we suggest that the LLP is attributed to the thermally assisted electron-hole recombination.

Annealing of nylon-1010 under high pressure

Full Paper: A study has been made on the annealing of nylon-1010 under high pressures. Heat treatment of melt-crystallized nylon-1010 was performed at 250degreesC for 30 min in the pressure range 0.7 similar to 2.5 GPa. It was found that the triclinic crystals of virgin nylon-1010 were retained at pressures less than 1.0 GPa or larger than 1.2 GPa. The X-ray diffraction intensity of (100) planes decreased with increasing pressure. The diffraction peaks shifted slightly to higher angles (2theta) relative to the virgin nylon-1010, indicating dense packing of polymer chains at high pressures. The highest melting temperature was 208degreesC for the sample annealed at 1.5 GPa. No extended-chain crystals were formed under the experimental conditions. Crosslinking occurred in the pressure range 1.0 similar to 1.2 GPa. The structure of the crosslinked samples was characterized by means of infrared spectroscopy and X-ray photoelectron spectroscopy. It is concluded that a mechanism of crosslinking via carbodiimide can explain the nature of crosslinking of nylon-1010 annealed at high pressures. The remarkable changes of the structure of annealed nylon-1010 are also discussed in this article.

Photoluminescence of organic-inorganic hybrid SiO2 xerogels

Organic-inorganic hybrid SiO2 xerogels were prepared by the sol-gel method under various preparation conditions and compositions by using tetraethoxysilane (TEOS), (3-aminopropyl) triethoxysilane (A-PS), (3-glycidoxypropyl) trimethoxysilane (GPS), organic acid (CH3COOH) and inorganic acids (HCl, HNO3, H2SO4) as the main precursors. Luminescence and FT-IR spectra were used to characterize the resulted hybrid SiO2 xerogels. The result of FT-IR spectrum shows that the xerogels are composed of non-crystalline -Si-O-Si- networks containing some organic groups such as -NH, -CH and -OH. Under the excitation of 365 nm, all the hybrid xerogels exhibit strong luminescence in the blue region, but the emission intensity and position depend on the starting precursor compositions to a large extent. Suitable amount of polyethylene glycol (PEG500 and PEG10000) in the hybrid xerogels can enhance the emission intensity. Additionally, the emission intensity of the hybrid xerogels increases with heat treatment temperature in the range of ambient to 200degreesC, and vacuum condition is also able to enhance the emission intensity.

Fabrication, patterning, and optical properties of nanocrystalline YVO4 : A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films via sol-gel soft lithography

Nanocrystalline YVO4:A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM) and optical microscopy, UV/vis transmission and absorption spectra, photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 400 degreesC and the crystallinity increased with the increase of annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of grains with an average size of 90 nm. Patterned gel and crystalline phosphor film bands with different widths (5-60 mum) were obtained. Significant shrinkage and a few defects were observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline YVO4 phosphor films because of an efficient energy transfer from vanadate groups to them. The Sm3+ and Er3+ ions also showed upconversion luminescence in a YVO4 film host. Both the lifetimes and PL intensity of the rare earth ions increased with increasing annealing temperature from 400 to 800 degreesC, and the optimum concentration for Eu3+ was determined to be 7 mol % and those for Dy3+, Sm3-, and Er3+ were 2 Mol % of Y3- in YVO4 films, respectively.

Preparation and characterization of novel luminescent sol-gel films containing a RE3+ carboxylic acid complex

RE3+ (Eu3+, Tb3+) complexes with carboxylic acid (salicylic acid and benzoic acid) were introduced into the sol, which was prepared by the hydrolysis of tetraethoxysilane (TEOS). A sol-gel luminescent thin film (SG-LTF) was then prepared by dispersing the sol onto a silica substrate by a spin coating method. Multi-layer luminescent thin films were prepared by repeating the same process. The luminescent spectra, fluorescence lifetime and thermal stability of the SG-LTFs were investigated. For the reason of comparison polyvinylbutyral (PVB) was added into a N,N-dimethylformamide (DMF) solution in which the comparative RE3+ carboxylic acid complexes were previously dissolved to form the DMF/PVB solution and the PVB luminescent thin film (PVB-LTF) was prepared. The results show that a broad excitation band indicates the formation of RE complexes in the solid SG-LTFs. RE ions, which are restrained in the silica matrix, present longer lifetimes and higher thermal stability than that in the PVB-LTF containing the corresponding pure complexes. The different doping concentration of RE (III) complexes in the SG-LTFs and the different change of the emission intensities with the heat treatment temperature in the sol-gel thin film and the sol-gel bulk gel were also discussed in this paper.