Materials Science Forum Vols. 663-665

Abstract: Metal nanoparticles are well-known to exhibit a strong interaction with light, which have very important applications and one of them, recent years, is optical trapping of the metallic nanoparticles. Based on the principle of the optical trapping for metallic nanoparticles, in this paper, the gradient forces and the scattering forces in the optical trapping for gold-, silver- and copper-nanoparticles have been analyzed and calculated numerically. Typical power spectra for gold-, silver- and copper-nanoparticles have been obtained. It is shown from the calculation results that under what condition these metallic nanoparticles can be trapped, and the stability of the potential well for these metallic nanoparticles has been analyzed in order to know whether the well was deep enough for overcoming the gravity and Brownian motion.

Abstract: A new electron trapping materials (ETM) SrS: Eu2+, Dy3+, which was prepared by the method of high temperature solid-state reaction. The results indicate that both ultraviolet light and visible light can be used as exciting source to store energy. After exposed under ultraviolet, the sample was stimulated by 980nm laser. As a result, an obvious luminescence at 615 nm was detected. The up-conversion emission spectrum was found to be a continuous broadband spectrum resulted from the multi-transitions of Eu2+ 4f6→4f7 (8S7/2). The emission peak intensity of SrS: Eu2+, Dy3+ was stronger than SrS: Eu2+.

Abstract: Novel single-phase Ca2-xBO3Cl:xDy3+ phosphors were synthesized at 900 oC in an activated carbon reducing atmosphere, and their luminescent properties were investigated by photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The optimal doping concentration of Dy3+ ions is found to be x=0.03 mol, and the nature of resonance energy transfer for Dy3+ ions is also discussed. Generation of white-light excited by 390 near-ultraviolet (n-UV) light shows that all the investigated phosphors lie within white region and the colour coordinate of Ca1.95BO3Cl:0.05Dy3+ (0.272, 0.326) is closer to the equal-energy white light point, which is potentially a good candidate as an n-UV-converted phosphor for white light-emitting diodes (LEDs).

Abstract: For the purpose of investigating the factors induced the non-band-edge excitation optical properties of water-soluble CdSe semiconductor quantum dots (QDs), the initial molar ratio of Cd and Se(or Cd/Se), the temperature of crystal nucleation and growing, the time of the growth etc. are systematically studied in the fabricated process. The properties of the as-prepared nano-particles (NPs) have been characterized by ultraviolet-visible absorption spectra (UV-Vis), photoluminescence (PL) spectroscopy, X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The measured results show that it is possible to exist surface trapping, impurities and other defect energy states in the products with the non-band-edge excitation PL properties, and all the characteristics are involved with the different synthetic routes and prepared techniques.

Abstract: CaMoO4: Eu3+ red phosphors were synthesized by co-precipitation method with H3BO3 as an additive and the relationship between H3BO3 doping amount and luminescent properties were studied. The brightness increased with increasing H3BO3 amount, the brightness of the CaMoO4: Eu3+ powder with 10 mol％ H3BO3 was 3.2 times higher than that of the phosphor without H3BO3.

Abstract: By means of SEM, TEM, UV-VIS optical transmission spectra and photoluminescence spectra tests, hetero-epitaxial defects and optical characteristics of SiCGe layers grown on 6H-SiC substrate were studied. SEM and TEM images have shown that the SiCGe were grown in layer-by-layer mode with APD and DPB defects which were caused by the thermal and lattice mismatches between SiCGe and SiC. Transmission spectra results have shown the calculated band gap of the SiCGe layer was 2.31eV. Room temperature photoluminescence spectra have shown that the peak wavelength and the FWHM of SiCGe layer were closely related to its Ge contents and the hetero-epitaxial defects.

Abstract: Dye-sensitized solar cell (DSSC) is considered as the next generation low cost photovoltaic device, and one of the important components is the counter electrode which reduces the I3- ions generated after electron injection from iodide into the oxidized sensitizer. In this work composite material of carbon black and LaCoO3 synthesized by sol-gel method has been investigated to replace the platinized counter electrode for quasi-solid-state dye-sensitized solar cells. From cyclic voltammogram, it was found that carbon black catalyzed with LaCoO3 exhibited increased reduction current compared with that of carbon black without LaCoO3. This was consistent with increased surface roughness depicted from scanning electron microscopy (SEM) image. The electrochemical impedance spectroscopy (EIS) of DSSCs using carbon black-LaCoO3 composite as counter electrode revealed lower charge-transfer resistance (Rct) than that using carbon black. The highest conversion efficiency of 5.40% was obtained from DSSC (active area 1 cm2) fabricated with quasi-solid composite polymer electrolyte using carbon black-LaCoO3 (95:5 ratio by weight) compared to 5.23% obtained from DSSC equipped with platinum counter electrode. The performances of the quasi-solid-state DSSCs sensitized with N719 and natural dyes were examined and it was concluded that the carbon black-LaCoO3 composite was compatible with platinum coated counter electrode for DSSCs.

Abstract: In this paper, the effect of the substrate on wireless sensor network (WSN) node’s RF performance is studied experimentally by using different substrate materials with different thickness. A six-layer FR4 substrate PCB WSN node is fabricated and compared with the original two-layer FR4 PCB node to show the impact of substrate material thickness. Also different substrate dielectric constants’ impacts are studied by the same method. All these demonstrators are modeling by RF circuit analysis method and simulated in the Ansoft Designer software. Simulation results match the experimental measurement. An optimization method based on simulation for WSN node design with different substrate is presented. This analysis, modeling, simulation and optimization procedure can be carried out on some novel substrate materials such as LTCC and LCP.

Abstract: X-ray photoelectron spectroscopy (XPS) has been employed to investigate the protonation degree of polyaniline doped with sulfosalicylic acid (PAni-SSA) obtained by different synthetic methods. The protonation degree has been compared to electrical conductivity. Prepared PAni-SSA through the redoping process in an agate mortar displays conductivity values within the range of 1S/cm. Protonation degree of synthesized PAni-SSA by aqueous dispersion polymerization of aniline in the presence of SSA is higher than 50 %, indicating that a substantial portion of amine units have also been protonated. The C/N and S/N molar ratios obtained by XPS analysis indicate that the polyaniline chains obtained by aqueous dispersion polymerization are protonated by both sulfate anions.

Abstract: The evolution operator method is applied to studying the time-dependent and spin-related electron transport through a magnetic quantum dot coupled to two normal-metal leads. When the microwave field is applied on quantum dot there are additional peaks of PAT current besides the main peak of resonant tunneling current, and the energy distance between peaks relate to the frequency of microwave fields. Furthermore, owe to the spin non-degeneration in the magnetic quantum dot, the spin-up and spin-down current peaks are separated, and the separated distance depends on Zeeman energy. These effects allow us to propose a scheme to control the magnitude and spin polarization of current.