Advanced Materials Research Vols. 306-307

Abstract: A new type rhodanine ramification 3-(4'-methoxyphenyl)-5 (2'- arsenoxylphenylazo)- rhodanine (4MORAAP) was prepared as fluorescent reagent in this paper. A new pectrofluorimetry method was proposed to determine the trace bismuth based on the reaction between potassium periodate and 4MORAAP. The fluorescence intensity was found to be quenched by the oxidation of 4MORAAP by potassium periodate with bismuth as catalyst in the buffer medium of potassium hydrogen phthalate-sodium hydroxide (pH=5.2). Under the optimum conditions, the fluorescent intensity was correlated to be linear with the concentration of bismuth over the range of 2.0×10^-7-1.8×10^-6 g×L^-1 and the detection limit was 2.9×10^-8 g×L^-1. The relative standard deviation (RSD) was 2.4 % for determined1.0×10^-6 g×L^-1 bismuth (n=11). The method was proved to be sensitive and selective and was successfully applied to determine trace bismuth in domestic water.

Abstract: The effect of charging current, temperature, concentrations of KOH and LiOH, soaking time and temperature on the utilization of metal hydride (MH) electrode in the formation of Ni/MH battery is investigated by the conventional experimental design. The experimental results indicate that the optimal charging conditions are the charging time ratio of 9/1 with 0.1 and 1.0 C-rates. The other optimal conditions for the formation of MH electrode re 25°C, 8.02 M KOH and 0.48 M LiOH aqueous solution. The steady utilization of MH electrode is 83.52% for the soaking temperature of 45°C and the soaking time greater than 24 h, respectively. According to the Taguchi's orthogonal arrays, the relationship between the utilization of metal hydride electrode (y) and the formation factors is obtained to be y = 75.52 - 6.58A + 3.98C + 5.09E + 6.71F - 1.32AC + 2.57BC + 5.62E² - 10.67F² where A, B, C, E and F are the charging current, the charging temperature, the concentration of KOH in the electrolyte, the soaking time and temperature, respectively. Under the optimal formation conditions, the utilization of MH electrode is increased from 87.25% to the steady value of 98.50% by increasing the charging/discharging cycle from 1 to 4.

Abstract: The mesoporous carbon (MC) synthesized by a one-step method with tetraethyl ortho- silicate (TEOS) as silicon source, sucrose as carbon source and phosphoric acid as active agent, respectively, is used as the support to prepare Pt/MC electrocatalysts. The pore characteristics and the graphitic extend of MC can be adjusted by controlling the carbonation temperature (T_c). The maximum surface area of home-made MC is confirmed and analyzed by BET to be 860.20 m2 g^-1 with Tc = 900 °C, and the main pore size of MC is 8.70 nm. The maximum mass activity (MA) and specific activity (SA) of the oxygen reduction reaction (ORR) on Pt/MC (P/Si = 0.5, T_c = 900 °C) are experimentally found to be 15.54 A g^-1 and 18.05 mA cm^-2, respectively.

Abstract: In this study, single-crystal TiO₂ nanorod (NR) arrays were used as the photoanodes of dye sensitized solar cells (DSSC). The post-annealing treatment was carried out in air, O₂, N₂ and vacuum atomsphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to characterize the structure, morphology and crystallity of these samples. Although the nanorod arrays which undergo annealing remained the single-crystal structure without any change in the morphology, considerable improvement in the nanorod solar cell performance was obtained. The high efficicency of 4.42 % was achieved in the cells containing nanorods which were annealed in air at 500 °C for 30 min. In comparison, the cell fabricated using TiO₂ samples without post- annealing treatment exhibited a low efficiency of just 2.1 %. Such a large improvement (280 %) was mainly attributed to the faster electron transport and the lower charge recombination rate after annealing due to an increase of the depletion width. Otherwise, the cell performance improvement may result from an enhancement in the adhension and electrical contact at the TiO₂/FTO interface. The in-depth study shows that the solar cell efficiency was strongly dependent on the annealing ambience, too.

Abstract: Synchrotron radiation extended X-ray absorption fine structure and Raman scattering were used to characterize a series of 3C-SiC films grown on Si (100) by chemical vapor deposition. EXAFS can probe the physical and chemical structure of matters at an atomic scale and Raman parameters such as intensity, width, peak frequency and polarization provide fruitful information on the crystal quality and properties of these film materials.

Abstract: Rare earth activated AlPO4 phosphors were synthesized by solid-state reactions and the completion of the synthesis was confirmed by X-ray diffraction (XRD) pattern. Under near-ultraviolet (nUV) light, the Eu3+ emission in AlPO4 consists of the transitions from 5D0 to 7FJ shows orange/red region and the AlPO4 :Dy3+ phosphor shows an efficient blue and yellow band emissions, which originates from the 4F9/26H15/2 and 4F9/26H13/2 transitions of Dy3+ ion. The excitation spectra of the phosphors are extending from 300 to 400 nm, which are characteristics of nUV excited LED. The effect of the Eu3+ and Dy3+ concentration on the luminescence properties of AlPO4 phosphors is also studied.

Abstract: Cr-doped rod-like ZnO particles with nominal 3 at% doping concentration were synthesized by hydrothermal method. The structural and optical properties of the sample were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and photoluminescence (PL). The results show that the as-synthesized product is of hexagonal wurtzite structure without metallic Cr or other secondary phases and the morphology of the ZnO particles is rod shaped. The room-temperature PL spectrum of the Cr-doped rod-like ZnO particles exhibits a strong blue emission at 440nm and two weak emission bands centered at 410nm and 565nm, respectively.

Abstract: A new silicon MEMS process has been proposed utilizing anodic bonding of an extremely thin silicon film (60 m) on a glass substrate, followed by photo lithographically defining micro spring structures on the silicon film and dry etching the silicon film using an inductively coupled plasma (ICP) dry etcher. After that, the underneath glass was selectively etched off using a hydrofluoric (HF) solution to release the micro spring. This technique was successfully applied to a micro vibration detection sensor with the silicon microspring with a cross section of 10 m x 60 m with a length longer than 500 m.

Abstract: P-channel pentacene field effect transistorswith a Si/SiO₂/pentacene/Au structure were fabricated, and were gamma-ray irradiated with a Co⁶⁰ source. The changes of the drain current I_D vs. source/drain voltage V_SD (I_D - V_SD) characteristics were measured after every 200 Gy in silicon (Gy_Si) irradiations up to the total dose of 1200 Gy_Si. The drain current I_D continuously decreased to less than 10 % of that before irradiation after 1200 Gy_Si irradiation. The threshold voltage V_th continuously decreased up to 800 Gy_Si, started to saturate above 800 Gy_Si, and recovered above 1000 Gy_Si. The mobility m continued to decrease up to 1200 Gy_Si. Those behaviors were explained by accumulation of positive trapped charge within the gate insulator SiO₂ near the interface, continuous increase of interface traps near the interface between the SiO₂ and pentacene, and build up of electrons in the channel regions. These behaviors were discussed in comparisons with previously reported results on ultraviolet (UV) light irradiation experiments on similarly structured pentacene-based transistors.

Abstract: A silicon condenser microphone on an SOI (silicon on insulator) substrate using only one photo mask was fabricated. This microphone consists of a diaphragm with the thickness of 20 μm and the diameter of 2 mm, a SiO2 insulative spacer (4-μm-thick buried oxide), and a 450-μm-thick silicon back plate with the meshed structures having extremely small (60 μm) hexagonal shaped acoustic holes. The gap between the 20-μm-thick silicon diaphragm and the back plate is 4 μm, which is determined by the thickness of the buried oxide in the SOI wafer. This microphone was confirmed to function as a static pressure sensor. The SOI microphone was also connected to an amplifier circuit, and exposed to the sound pressure of 110 dB at the frequency of 1 kHz. The microphone clearly responded to the input sound, and the output ac voltage of approximately 40 V was detected.