Ultra-long Pt nanolawns supported on TiO2-coated carbon fibers as 3D hybrid catalyst for methanol oxidation

In this study, TiO2 thin film photocatalyst on carbon fibers was used to synthesize ultra-long single crystalline Pt nanowires via a simple photoreduction route (thermally activated photoreduction). It also acted as a co-catalytic material with Pt. Taking advantage of the high-aspect ratio of the Pt nanostructure as well as the excellent catalytic activity of TiO2, this hybrid structure has the great potential as the active anode in direct methanol fuel cells. The electrochemical results indicate that TiO2 is capable of transforming CO-like poisoning species on the Pt surface during methanol oxidation and contributes to a high CO tolerance of this Pt nanowire/TiO2 hybrid structure

Direct growth of ultra-long platinum nanolawns on a semiconductor photocatalyst

A template- and surfactant-free process, thermally assisted photoreduction, is developed to prepare vertically grown ultra-long Pt nanowires (NWs) (about 30-40 nm in diameter, 5-6 μm in length, and up to 80 NWs/100 μm2 in the wire density) on TiO2 coated substrates, including Si wafers and carbon fibers, with the assistance of the photocatalytic ability and semiconductor characteristics of TiO2. A remarkable aspect ratio of up to 200 can be achieved. TEM analytical results suggest that the Pt NWs are single-crystalline with a preferred 〈111〉 growth direction. The precursor adopted and the heat treatment conditions are crucial for the yield of NWs. The photoelectrons supplied by TiO2 gives rise to the formation of nano-sized Pt nuclei from salt melt or solution. The subsequent growth of NWs is supported by the thermal electrons which also generated from TiO2 during the post thermal treatment. The interactions between the ions and the electrons in the Pt/TiO2 junction are discussed in this study

An in situ study on the coalescence of monolayer-protected Au-Ag nanoparticle deposits upon heating

The structural evolution of thiolate-protected nanoparticles of gold, silver, and their alloys with various Au/Ag ratios (3:1, 1:1, and 1:3) upon heating was investigated by means of in situ synchrotron radiation X-ray diffraction. The relationships between the coalescence and composition of nanoparticles, as well as the surfactant reactions, were clarified. Experimental results show that there existed a critical temperature ranging from 120°C to 164°C, above which the tiny broad X-ray diffraction peaks became sharp and strong due to particle coalescence. The coalescence temperatures for alloy nanoparticle deposits were clearly lower than those for pure metals, which can be ascribed to the rivalry between the thermodynamic effect due to alloying and the interactions between surface-assembled layers and the surface atoms of the nanoparticles. The strong affinity of thiolates to Ag and thus complex interactions give rise to a greater energy barrier for the coalescence of nanoparticles into the bulk and subsequent high coalescence temperature. The influences of particle coalescence on the optical and electrical properties of the nanoparticle deposits were also explored

Synthesis, formation and characterization of ZnTiO3 ceramics,Ceram

Abstract Zinc titanate (ZnTiO 3 ) powders of perovskite structure were synthesized by conventional solid state reaction using metal oxides. Powders of ZnO and TiO 2 in a molar ratio of 1:1 were mixed in a ball mill and then heated at temperatures from 700 to 1000 • C for various time periods in air. The crystallization temperature of ZnTiO 3 powder was ∼820 • C, activation energy for crystallization was ∼327.14 kJ/mol and for grain growth was ∼48.84 kJ/mol. A transition point was observed when the electrical resistivity was measured versus temperature. Like some ferroelectric materials, a PTCR behavior above the transition temperature was observed with Curie temperature of ∼5 • C

Role of fruit juice in achieving the 5-a-day recommendation for fruit and vegetable intake

Although there is strong evidence that consumption of fruit and vegetables is associatedwith a reduced rate of all-cause mortality, only a minority of the population consumes5 servings a day, and campaigns to increase intake have had limited success.This review examines whether encouraging the consumption of fruit juice might offera step toward the 5-a-day target. Reasons given for not consuming whole fruit involvepracticalities, inconvenience, and the effort required. Psychologically, what isimportant is not only basic information about health, but how individuals interprettheir ability to implement that information. It has been argued that fruit juice avoidsthe problems that commonly prevent fruit consumption and thus provides a practicalmeans of increasing intake and benefitting health through an approach with whichthe population can readily engage. Those arguing against consuming fruit juice emphasizethat it is a source of sugar lacking fiber, yet juice provides nutrients such asvitamin C, carotenoids, and polyphenols that offer health-related benefits. Actively encouragingthe daily consumption of fruit juice in public health policy could help populationsachieve the 5-a-day recommendation for fruit and vegetable intake

Kinetic study of Pt nanocrystal deposition on Ag nanowires with clean surfaces via galvanic replacement

Without using any templates or surfactants, this study develops a high-yield process to prepare vertical Ag-Pt core-shell nanowires (NWs) by thermally assisted photoreduction of Ag NWs and successive galvanic replacement between Ag and Pt ions. The clean surface of Ag nanowires allows Pt ions to reduce and deposit on it and forms a compact sheath comprising Pt nanocrystals. The core-shell structural feature of the NWs thus produced has been demonstrated via transmission electron microscopy observation and Auger electron spectroscopy elemental analysis. Kinetic analysis suggests that the deposition of Pt is an interface-controlled reaction and is dominated by the oxidative dissolution of Ag atoms. The boundaries in between Pt nanocrystals may act as microchannels for the transport of Ag ions during galvanic replacement reactions

Photoluminescence enhancement of ZnS : Mn nanoparticles by SiO2 coating

ZnS:Mn nanoparticles (~3.1?nm) of a cubic structure were prepared by a coprecipitation method and then dispersed with various weights (0.5-8?g) into a solution containing ammonium hydroxide, ethanol and tetraethyl orthosilicate (TEOS) for surface coating. X-ray diffraction (XRD) analysis of these coated ZnS:Mn powders revealed the presence of amorphous materials after the coating process. Characterization of the coated powders using a transmission electron microscope (TEM) and an electron energy loss spectrometer (EELS) showed that ZnS:Mn nanoparticles were randomly embedded in the larger particles of amorphous SiO2 (50-100?nm). The optical properties of photoluminescence (PL) and diffuse reflection of the SiO2-coated ZnS:Mn powders were found to depend on the quantity of ZnS:Mn nanoparticles in the coating solution. The increased PL intensity of ZnS:Mn at 590?nm after SiO2 coating was proposed to result from the inhibition of excitation energy transfer to quenching centers or surface states based on the observation of the reduced absorption in the region of 370-450?nm.NRC publication: Ye