Surface-enhanced vibrational spectroscopy of adsorbates on microemulsion synthesized gold nanoparticles

Very small (<10 nm) monodisperse gold nanoparticles (AuNPs) coated with a monolayer of decanethiol were prepared and their surface-enhanced infrared absorption (SEIRA) spectra were measured in the transmission mode. The AuNPs were prepared by the borohydride reduction of HAuCl(4) inside reverse micelles that were made by adding water to a hexane solution of sodium bis(2-ethylhexyl)sulfosuccinate (AOT). The gold nanoparticles were then stabilized by the addition of decanethiol. Subsequent addition of p-nitrothiophenol both facilitated the removal of excess AOT and showed that the gold surface was completely covered by the decanethiol. SEIRA spectra of decanethiol on gold particles prepared in AOT microemulsions were about twelve times more intense than corresponding layers on gold produced by electroless deposition and gave a significantly less noisy spectrum compared to the corresponding surface-enhanced Raman spectrum. The surface-enhanced Raman scattering (SERS) spectra of the same samples showed that the most intense spectrum was obtained from gold nanoparticles with a mean diameter of 2.5 nm. This result is in contrast to previous statements that SERS spectra could only be obtained from particles larger than 10 nm.     

Deposition of metal nanoparticles on carbon nanotubes via hexane modified water-in-CO2 microemulsion at room temperature

Carbon nanotube-supported metallic nanoparticles (Pd, Rh, and bimetallic Pd-Rh) with diameters in the range 2-10 nm can be synthesized by hydrogen reduction of metal ions dissolved in the water core of a CO2 microemulsion in liquid CO2 at room temperature. The microemulsion is stabilized by sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and dissolved in liquid CO2 with the aid of hexane as a modifier. The metal nanoparticles synthesized in the microemulsion can be deposited on surfaces of multi-walled carbon nanotubes (MWCNTs) by stirring in the liquid CO2 phase. This simple method produces uniformly distributed metal nanoparticles on surfaces of the MWCNTs with high yields. The carbon nanotube-supported Pd/Rh bimetallic nanoparticles exhibit high catalytic activities for hydrogenation of aromatic compounds and can be reused without losing catalytic activity.     

Improve the luminous efficiency of AC plasma display by high-frequency driving on address electrodes

A novel high-frequency driving scheme was proposed in this paper to improve the luminous efficiency of a plasma display. High-frequency oscillating waveform was applied to the address electrodes of the conventional three-electrodes AC-type plasma display panel during the sustaining period. More vacuum ultraviolet rays were generated by the high-frequency waveform so that the luminance and luminous efficiency could be enhanced. From experiments on an 8.5-in panel, the luminance was improved and the luminous efficiency was enhanced more than 40%.     

Factors Affecting the Preparation of Barium Titanyl Oxalate Tetrahydrate

Several experiments have been conducted to investigate the preparation of barium titanyl oxalate tetrahydrate (BTO). Differential thermal analysis and thermogravimetric analysis were employed to investigate the thermal decomposition, and an X-ray diffractometer and a transmission electron microscope were used to analyze the phases and crystalline states. It has been found that BTO is a nonstoichiometric compound, in which barium hydrogen oxalate hydrate was inserted by the titanium species. Moreover, it has been shown that a mixture would from rather than BTO, depending on pH, mixing order, and oxalate solution.     

Formation Mechanisms of La3+-Doped CaO·6Fe2O3 with the Magnetoplumbite Structue

Several experiments were conducted to investigate the formation mechanisms of the magnetoplumbite phase in La³⁺-doped CaO 6Fe₂O₃. It is shown that the CaO·2Fe₂O₃ phase plays a crucial role in forming the magnetoplumbite phase. The formation mechanisms are proposed and verified.     

Pt, Rh and Pt-Rh nanoparticles on modified single-walled carbon nanotubes for hydrogenation of benzene at room temperature

Nanometer-sized Pt, Rh, and bimetallic Pt-Rh particles can be deposited on surface of phenylacetic acid functionalized single-walled carbon nanotubes (SWCNTs) by a microemulsion method. The SWCNT-supported metallic nanoparticles show much greater catalytic activities compared with commercially available carbon-supported Pt and Rh catalysts for hydrogenation of neat benzene under mild experimental conditions. The bimetallic Pt-Rh nanoparticle catalyst synthesized by this method shows an enhanced activity relative to individual SWCNT-supported Pt and Rh nanoparticle catalysts. The SWCNT-supported metal nanoparticle catalysts can be recycled and reused at least five times without losing their activity. The hydrogenation reactions performed under our experimental conditions would not affect the pi-pi stacking holding phenylacetic acid on SWCNT surface.     

Deposition of platinum nanoparticles on carbon nanotubes by supercritical fluid method

Carbon nanotube-supported platinum nanoparticles with a 5-15 nm diameter size range can be synthesized by hydrogen reduction of platinum(ll) acetylacetonate in methanol modified supercritical carbon dioxide. X-ray photoelectron spectroscopy and X-ray diffraction spectra indicate that the carbon nanotubes contain zero-valent platinum metal and high-resolution transmission electron microscopy images show that the visible lattice fringes of platinum nanoparticles are crystallites. Carbon nanotubes synthesized with 25% by weight of platinum nanoparticles exhibit a higher activity for hydrogenation of benzene compared with a commercial carbon black platinum catalyst. The carbon nanotube-supported platinum nanocatalyst can be reused at least six times for the hydrogenation reaction without losing activity. The carbon nanotube-supported platinum nanoparticles are also highly active for electrochemical oxidation of methanol and for reduction of oxygen suggesting their potential use as a new electrocatalyst for proton exchange membrane fuel cell applications.     

An energy-recovery sustaining driver with discharge currentcompensation for AC plasma display panel

A novel driver with discharge current compensation is proposed to drive an AC plasma display panel (PDP). This proposed circuit uses resonance between the inductor and the AC PDP to avoid abrupt charging/discharging. The four switches of the full bridge are all operated with zero-voltage-switching turn-on. In addition, an 8-in AC PDP equipped with the proposed driving circuit, operating at 100 kHz, is investigated. With the discharge current compensation, the experimental results show that the proposed driver can maintain the AC PDP to light at lower voltage (129 V)     

Thermal Analysis of Precursors of Barium Titanate Prepared by Coprecipitation

Thermal analysis was performed on coprecipitated materials and on individual components. The detailed decomposition schemes of coprecipitates and individual components are proposed and discussed. According to the proposed decomposition schemes, the values of the observed weight loss are in good agreement with those of the theoretical values of the coprecipitated materials and individual components. The results indicate that barium titanyl oxalate is an inserting compound, i.e., a structure of distorted barium hydrogen oxalate hydrate being inserted by Ti(OH)₃⁺. The results also verify that copreciptation of barium and titanium ions in an oxalate aqueous solution at pH 7 is a mixture of BaC₂O₄· 0.5H₂O and TiO(OH)₂· 1.5H₂O and coprecipitation of barium and titanium ions using the process of Yamamura et al. is a mixture of Ba(NO₃)₂ and Ti(OH)₂C₂O₄.     

Regenerative power electronics driver for plasma display panel insustain-mode operation

A regenerative power electronic circuit is proposed to drive a plasma display panel (PDP) in sustain-mode operation. This driver utilizes inductors to resonate with the equivalent intrinsic capacitance of the PDP to avoid the abrupt charging/discharging operation. The energy losses due to conventional hardswitching driving and the displacement current of the PDP are mainly recovered. Compared with prior approaches, this driving circuit has a quite simple structure and is suitable for asymmetrical operation