Novel Hybrid Electrocatalyst with Enhanced Performance in Alkaline Media: Hollow Au/Pd Core/Shell Nanostructures with a Raspberry Surface

In this paper, a hollow Au/Pd core/shell nanostructure with a raspberry surface was developed for methanol, ethanol, and formic acid oxidation in alkaline media. The results showed that it possessed better electrocatalyst performance than hollow Au nanospheres or Pd nanoparticles. The nanostructure was fabricated via a two-step method. Hollow Au nanospheres were first synthesized by a galvanic replacement reaction, and then they were coated with a layer of Pd grains. Several characterizations such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to investigate the prepared nanostructures.

Preparation of Hollow Carbon and Silicon Carbide Fibers with Different Cross-Sections by using Electrospun Fibers as Templates

Hollow carbon nanofibers with circular and rectangular opening were prepared by using electrospun silica fibers as templates. Silica fibers were synthesized by electrospinning, and they were coated with a carbon layer formed by thermal decomposition and carbonization of polystyrene under a nitrogen atmosphere. Hollow carbon nanofibers with circular and rectangular openings were then obtained after the silica core was etched by hydrofluoric acid. The carbon nanofibers with different morphologies also could be used as templates to fabricate silicon carbide fibers. The silicon carbide fibers with circular and rectangular openings could be obtained by using hollow carbon nanofibers and carbon belts as templates, respectively.

General and Facile Method To Prepare Uniform Y2O3:Eu Hollow Microspheres

Well-shaped Y2O3:Eu hollow microspheres have been successfully prepared on a large scale via a urea-based homogeneous precipitation technique in the presence of colloidal carbon spheres as hard templates followed by a subsequent heat treatment process. XRD results demonstrate that all the diffraction peaks of the samples can be well indexed to the pure cubic phase Of Y2O3. TEM and SEM images indicate that the shell of the uniform hollow spheres, whose diameters are about 250 nm, is composed of many uniform nanoparticles with diameters of about 20 nm, basically consistent with the estimation of XRD results. Furthermore, the main process in this method was carried out in aqueous condition, without the use of organic solvents or etching agents. The as-prepared hollow Y2O3:Eu microspheres show a strong red emission corresponding to the D-5(0)-F-7(2) transition of the Eu3+ ions under ultraviolet or low voltage excitation, which might find potential applications in fields such as light phosphor powders, advanced flat panel displays, field emission display devices, and biological labeling.

High-efficiency and low-cost hybrid nanomaterial as enhancing electrocatalyst: Spongelike AWN core/shell nanomaterial with hollow cavity

A high-efficiency and low-cost spongelike Au/Pt core/shell electrocatalyst with hollow cavity has been facilely obtained via a simple two-step wet chemical process. Hollow gold nanospheres were first synthesized via a modified galvanic replacement reaction between Co nanoparticles in situ produced and HAUCl(4). The as-prepared gold hollow spheres were employed as seeds to further grow spongelike Pt shell. It is found that the surface of this hybrid nanomaterial owns many Pt nanospikes, which form a spongelike nanostructure. All experimental data including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis-near-infrared spectroscopy have been employed to characterize the obtained Au/Pt hybrid nanomaterial. The rapid development of fuel cell has inspired us to investigate the electrocatalytic properties for dioxygen and methanol of this novel hybrid nanomaterial. Spongelike hybrid nanomaterial mentioned here exhibits much higher catalytic activity for dioxygen reduction and methanol oxidation than the common Pt electrode.

A simple method to prepare titania nanomaterials of core-shell structure, hollow nanospheres and mesoporous nanoparticles

A simple method to prepare titania nanomaterials of core-shell structure, hollow nanospheres and mesoporous nanoparticles has been developed. The core-shell nanostructures with NH4Cl as core and TiO2 center dot xH(2)O-NH4Cl as shell were prepared in nonaqueous system by the deposition on the surface of the aggregated NH4Cl crystals, which could be transformed into mesoporous anatase nanoparticles or hollow nanospheres by calcination at 500A degrees C or extraction with methanol, respectively. The hierarchical mesoporous nanostructures benefited the photocatalytic activities of the resultant titania nanomaterials, demonstrated by the UV light photodegradation of Methyl Orange.

Raspberry-like Hierarchical Au/Pt Nanoparticle Assembling Hollow Spheres with Nanochannels: An Advanced Nanoelectrocatalyst for the Oxygen Reduction Reaction

In this contribution, we for the first time report the synthesis of raspberry-like hierarchical Au/Pt nanoparticle (NP) assembling hollow spheres (RHAHS) with pore structure and complex morphology through one in situ sacrificial template approach without any post-treatment procedure. This method has some clear advantages including simplicity, quickness, high quality, good reproducibility, and no need of a complex post-treatment process (removing templating). Furthermore, the present method could be extended to other metal-based NP assembling hollow spheres. Most importantly, the as-prepared RHAHS exhibited excellent electrocatalytic activity for oxygen reduction reaction (ORR). For instance, the present RHAHS-modified electrode exhibited more positive potential (the half-wave potential at about 0.6 V), higher specific activity, and higher mass activity for ORR than that of commercial platinum black (CPB). Rotating ring-disk electrode (RRDE) voltarnmetry demonstrated that the RHAHS-modified electrode could almost catalyze a four-electron reduction of O-2 to H2O in a 0.5 M air-saturated H2SO4 solution.

Synthesis of Arm-6 polystyrene by atom transfer radical polymerization

A new initiator for atom transfer radical polymerization (ATRP), (Cl-2 HCCOO)(3) -C-6 H-3, (TrDCAP),has been designed and successfully synthesized. ATRP of styrene was carried out by using TrDCAP as hexafunctional initiator and the CuCl/bpy catalyst at 130 degrees C in 30% THF via core-first strategy. The Arm-6 PS-AAP was synthesized by etherealization of Arm-6 PS and 4-(4'-methoxyphenylazomethine) phenol (AAP). The initiator and the architectures of the Arm-6 PS were confirmed by H-1-NMR, FT-IR, UV-Vis and GPC.

Synthesis of a (sic)-shaped amphiphilic block copolymer by the combination of atom transfer radical polymerization and living anionic polymerization

The functionalization of monomer units in the form of macroinitiators in an orthogonal fashion yields more predictable macromolecular architectures and complex polymers. Therefore, a new there exists E-shaped amphiphilic block copolymer, (PMMA)(2)-PEO-(PS)(2)-PEO-(PMMA)(2) [where PMMA is poly(methyl methacrylate), PEO is poly (ethylene oxide), and PS is polystyrene], has been designed and successfully synthesized by the combination of atom transfer radical polymerization (ATRP) and living anionic polymerization. The synthesis of meso-2,3-dibromosuccinic acid acetate/diethylene glycol was used to initiate the polymerization of styrene via ATRP to yield linear (HO)(2)-PS2 with two active hydroxyl groups by living anionic polymerization via diphenylmethylpotassium to initiate the polymerization of ethylene oxide. Afterwards, the synthesized miktoarm-4 amphiphilic block copolymer, (HO-PEO)(2)-PS2, was esterified with 2,2-dichloroacetyl chloride to form a macroinitiator that initiated the polymerization of methyl methacrylate via ATRP to prepare the there exists E-shaped amphiphilic block copolymer.

A third-generation H2O2 biosensor based on horseradish peroxidase-labeled Au nanoparticles self-assembled to hollow porous polymeric nanopheres

A novel third-generation biosensor for hydrogen peroxide (H2O2) was developed by self-assembling gold nanoparticles to hollow porous thiol-functionalized poly(divinylbenzene-co-acrylic acid) (DVB-co-AA) nanospheres. At first, a cleaned gold electrode was immersed in hollow porous thiol-functionalized poly(DVB-co-AA) nanosphere latex to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups of the nanospheres. Finally, horseradish peroxidase (HRP) was immobilized on the surface of the gold nanoparticles. The immobilized horseradish peroxidase exhibited direct electrochemical behavior toward the reduction of hydrogen peroxide. The resulting biosensor showed a wide linear range of 1.0 mu M-8.0 mM and a detection limit of 0.5 mu M estimated at a signal-to-noise ratio of 3. Moreover, the studied biosensor exhibited high sensitivity, good reproducibility, and long-term stability.

Hydrothermal synthesis of spherical and hollow Gd2O3 : Eu3+ phosphors

Spherical and submicrometer-sized hollow Gd2O3:Eu3+ phosphors were prepared by homogeneous precipitation and hydrothermal method by varying the concentrations of reactants and changing the synthesis conditions. In the precipitation step, the spherical nucleus was formed and grew to large particles. In the hydrothermal step, the large particles crystallized to solid or hollow spheres. At last, Gd2O3:Eu3+ phosphors were obtained by annealing at the temperature more than 600 degrees C. The deduced mechanics of forming the solid and hollow spheres was proposed. And the obtained spherical Gd2O3:Eu3+ phosphors had better red luminescence properties. The relative luminescence intensity and the lifetime increased with increasing annealing temperatures.