Nanoelectrocatalyst based on high-density Au/Pt hybrid nanoparticles supported on a silica nanosphere

A high-efficiency nanoelectrocatalyst based on high-density Au/Pt hybrid nanoparticles supported on a silica nanosphere (Au-Pt/SiO2) has been prepared by a facile wet chemical method. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy are employed to characterize the obtained Au-Pt/SiO2. It was found that each hybrid nanosphere is composed of high-density small Au/Pt hybrid nanoparticles with rough surfaces. These small Au/Pt hybrid nanoparticles interconnect and form a porous nanostructure, which provides highly accessible activity sites, as required for high electrocatalytic activity. We suggest that the particular morphology of the AuPt/SiO2 may be the reason for the high catalytic activity. Thus, this hybrid nanomaterial may find a potential application in fuel cells.

Gold/platinum hybrid nanoparticles supported on multiwalled carbon nanotube/silica coaxial nanocables: Preparation and application as electrocatalysts for oxygen reduction

A simple approach combining sonication and sol-gel chemistry was employed to synthesize silica coated carbon nanotube (CNTs) coaxial nanocables. It was found that a homogeneous silica layer can be coated on the surface of the CNTs. This method is simple, rapid, and reproducible. Furthermore, gold nanoparticle supported coaxial nanocables were facilely obtained using amino-functionalized silica as the interlinker. Furthermore, to reduce the cost of Pt in fuel cells, designing a Pt shell on the surface of a noble metal such as gold or silver is necessary. High-density gold/platinum hybrid nanoparticles were located on the surface of I-D coaxial nanocables with high surface-to-volume ratios. It was found that this hybrid nanomaterial exhibits a high electrocatalytic activity for enhancing oxygen reduction (low overpotential associated with the oxygen reduction reaction and almost four-electron electroreduction of dioxygen to water).

The effect of template phase on the structures of As-synthesized silica nanoparticles with fragile didodecyldimethylammonium bromide vesicles as templates

The effect of template phase on the structures of as-synthesized silica nanoparticles with fragile DDAB vesicles as templates is reported. It is found that the template phase plays a critical role in the growth process of silica: the unstable DDAB vesicles in liquid-crystalline phase often lead to the formation of mesostructured solid spheres, and the rather stable DDAB vesicles in gel phase lead to the formation of hollow spheres with less mesostructures.

A novel sensitive solid-state electrochemiluminescence sensor material: Ru(bpy)(2+)(3) doped SiO2@MWNTs coaxial nanocable

A simple, large scale, and one-step process for the preparation of tris(2,2'-bipyridyl)ruthenium(I) (Ru(bpy)(3)(2+)) doped SiO2@carbon nanotubes (MVNTs) coaxial nanocable used for an ultrasensitive electrochemiluminescence (ECL) is presented for the first time. More importantly, a directly coated as-formed functional material on ITO electrode surface exhibits excellent ECL behavior, good stability, and high sensitivity in the presence of tripropylamine (TPA). This novel functional material will find potential applications in biosensor, electrophoresis and electroanalysis.

Sol-gel synthesis and characterization of SiO2@NaGd(WO4)(2): Eu3+ core-shell-structured spherical phosphor particles

Monodisperse, core-shell-structured SiO2@NaGd(WO4)(2):Eu3+ particles were prepared by the sol-gel method. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence (PL), and low-voltage cathodoluminescence (CL) as well as time-resolved PL spectra and lifetimes. PL and CL study revealed that the core-shell-structured SiO2@NaGd (WO4)(2):Eu3+ particles show strong red emission dominated by the D-5(0) - F-7(2) transition of Eu3+ at 614 nm with a lifetime of 0.74 ms. The PL and CL emission intensity can be tuned by the coating number of NaGd(WO4)(2):Eu3+ phosphor layers on SiO2 and by accelerating voltage and the filament current, respectively.

Synthesis and characterization of monodisperse spherical core-shell structured SiO2@Y3Al5O12 : Ce3+/Tb3+ phosphors for field emission displays

Nanocrystalline Y3Al5O12: Ce3+/Tb3+ ( average crystalline size 30 nm) phosphor layers were coated on non-aggregated, monodisperse and spherical SiO2 particles by the sol-gel method, resulting in the formation of core-shell structured SiO2@Y3Al5O12:Ce3+/Tb3+ particles. X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the core-shell structured SiO2@Y3Al5O12: Ce3+/Tb3+ phosphor particles. The obtained core-shell structured phosphors consist of well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the Y3Al5O12:Ce3+/Tb3+ shells on the SiO2 cores ( average size about 500 nm, crystalline size about 30 nm) could be easily tailored by varying the number of deposition cycles (100 nm for four deposition cycles). Under the excitation of ultraviolet and low-voltage electron beams (1-3 kV), the core-shell SiO2@Y3Al5O12:Ce3+/ Tb3+ particles show strong yellow-green and green emission corresponding to the 5d-4f emission of Ce3+ and D-5(4)-F-7(J) ( J = 6, 5, 4, 3) emission of Tb3+, respectively.

Investigation of the gel effect in reactive extrusion processes for free radical polymerization

The gel effect in the reactive extrusion process for free radical polymerization in a closely intermeshing co-rotating twin screw extruder was investigated. First the reaction kinetic model was constructed mainly on the basis of entanglement theory. Next, numerical calculation expressions for the initiator and monomer concentrations, monomer conversion, average molecular weight and apparent viscosity were deduced. Finally, the evolution of the above variables were shown and discussed for the example of butyl methacrylate. The simulated results of the monomer conversion are in good agreement with experimental results.

Synthesis and luminescent properties of europium (III) schiff base complexes covalently bonded to silica xerogels

A new kind of luminescent organic-inorganic hydrid material consisting of Eu(III)-schiff base complex covalently bonded to silica xerogel was synthesized via the sol-gel method using a Eu (N-propylene salicylimine ligand) complex modified with pendant triethoxysilane groups (Eu(III)(salenHSi)). The Eu(III)(salenHSi) complex is characterized by Fourier transform infrared (FT-IR) spectroscopy. Luminescent properties of the complex and the resulted hybrid silica xerogels have been investigated at room temperature.

Sol-gel deposition and luminescence properties of LiYF4 : Tb3+ thin films

Tb3+-doped LiYF4 films were deposited on quartz glass by a simple sol-gel method. X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), photoluminescence spectra, and lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 300 degrees C and fully crystallized at 400 degrees C. AFM and FESEM images of singly coated LiY0.95Tb0.05F4 annealed at 400 degrees C indicated that the film is uniform and crack-free films with average grain size of 90 nm, root mean square roughness of 11 nm and thickness of 120 nm. The doped Tb3+ ions showed its characteristic emission in crystalline LiYF4 films, i.e., D-5(3), F--7(4)J (J = 6, 5, 4, 3) emissions. The optimum doping concentration of the Tb3+ was determined to be 5.0 mol% of Y3+ in LiYF4 films.

Pechini sol-gel deposition and luminescent properties of SrLa1-xRExGa3O7 (RE = Eu, Tb) phosphor films

SrLa1-xRExGa3O7 (RE = EU3+, Tb3+) phosphor films were deposited on quartz glass substrates by a simple Pechim sol-gel method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy, field-emission scanning electron microscopy, photoluminescence spectra, and lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 700 degrees C and crystallized fully at 900 degrees C. The results of FNR spectra were in agreement with those of XRD. Uniform and crack-free films annealed at 900 degrees C were obtained with average grain size of 80 nm, root mean square roughness of 46 nm and thickness of 130 nm The RE ions showed their characteristic emission in crystalline SrLa1-xRExGa3O7 films, i.e., Eu3+ D-0-F-7(J) (J = 0, 1, 2, 3, 4), Tb3+5D4 -(7) F-J (J = 6, 5, 4, 3) emissions, respectively. The optimum concentrations (x) of Eu3+ and Tb3+ were determined to be 50, and 80 mol% in SrLa(1-x)RE(x)GGa(3)O(7) films, respectively.

Direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized in sol-gel-derived ceramic-carbon nanotube nanocomposite film

The sol-gel-derived ceramic-carbon nanotube (SGCCN) nanocomposite film fabricated by doping multiwall carbon nanotubes (MWNTs) into a silicate get matrix was used to immobilize protein. The SGCCN film can provide a favorable microenvironment for horseradish peroxidase (HRP) to perform direct electron transfer (DET) at glassy carbon electrode. The HRP immobilized in the SGCCN film shows a pair of well-defined redox waves and retains its bioelectrocatalytic activity to the reduction of O-2 and H2O2, which is superior to that immobilized in silica sol-gel film.

Extending electrochemical activity of polyaniline to alkaline media via electrostatic interaction and sol-gel route

The electroactivity of polyaniline was extended to pH = 14 alkaline media by preparation of a novel electrostatic interaction conductive hybrid from water-borne conductive polyaniline and silica network containing carboxyl groups via sol-gel process. In addition, the obtained conductive polyaniline hybrid film displayed very low conductivity threshold percolation and demonstrated excellent stability upon cycling.

Conductive hybrid film from polyaniline and polyurethane-silica

In order to improve the mechanical performance and water resistance of water-borne conducting polyaniline film, conducting polyaniline/polyurethane-silica hybrid film was prepared in aqueous solution employing silanol-terminated polyurethane and methyltriethoxysilane as sol-gel precursors. The hybrid film showed surface resistivity of 10(8) Omega even though the conducting polyaniline loading was only 10 wt% (or 1.5 wt% of polyaniline), and the mechanical performance as well as water resistance was significantly improved, making it suitable for antistatic application. Therefore, a practical route to water-borne processing of conducting polyaniline is disclosed.

Non-isothermal crystallisation kinetics of polyamide 6/mesoporous silica nanocomposites

Non-isothermal crystallisation kinetics of a polyamide 6/mesoporous silica nanocomposite (PA6-MS) has been investigated by differential scanning calorimetry (DSC) at different cooling rates. Mandelkern, Jeziorny-Ziabicki and Ozawa methods were applied to describe this crystallisation process. The analyses show that the mesoporous silica particles act as nucleating agents in the composite and that the Avrami exponent n varies from 3.0 to 4.6. The addition of mesoporous silica influenced the mechanism of nucleation and the growth of polyamide 6 (PA6) crystallites.