Advanced Materials Research Vols. 535-537

Abstract: We have prepared the rubrene microparticles through a solvent evaporation process, during which the as-prepared microparticles were immobilized directly onto ITO electrode. It is found that the rubrene microparticles exhibit strong electrochemiluminescent emission in the presence of the co-reactant tripropylamine. The rubrene microparticles can be employed as an electrochemiluminescent sensor, chemically and biologically, for detection of methylene blue and glucose. This work demonstrates that the microstructured architecture of electroluminescent organic molecule is applicable as emitter in electrochemiluminescent sensor.

Abstract: A series of multi-branched pyrazine derivatives have been synthesized, of which, the two-branched one with para-branching pattern shows much enhanced two-photon absorption cross section (σ) than that with meta-branching pattern (1.8 times). The three-branched pyrazine derivative, in which the branches are at ortho- or para-position, show strong two-photon absorption properties (σ=753GM), while its s-triazine analogue TSTA, with all the branches in meta-position, exhibit too weak two-photon excited fluorescence to be detected. These results indicate great effects of branching pattern on two-photon absorption.

Abstract: The structural and optical properties of InxGa1-xN/GaN multi-quantum wells (MQWs) grown on sapphire are discussed. Two kinds of InxGa1-xN/GaN MQWs with same period and different single cycle thickness and different growth temperature of MQWs are selected. Firstly, from the result of SRXRD and RBS/C, we can estimate that indium content of InxGa1-xN /GaN MQWs is 0.033 and 0.056, the single cycle thickness of MQWs is 13.04nm and 15.86nm respectively. Secondly the PL results indicate the optical properties of InxGa1-xN/GaN MQWs. Finally, we find indium content decreasing with increasing growth temperature of MQWs and the emission intensity reducing with temperature increasing, the emission optical peak position versus temperature show the “S-shaped” character. All these experimental results testify the material design of InxGa1-xN/GaN MQWs will have potential applications in spectral LED.

Abstract: In order to improve the corrosion resistance of sintered NdFeB magnet, experiments are done by the new process which involves ultrasonic electroforming Ni–P alloys. The influence of ultrasonic on electroforming Ni–P alloy on NdFeB was studied by using microscope, adhesion test and NaCl solution immersion test.The results showed that the Ni–P alloy deposit on NdFeB is rough and has poor adhesion without ultrasonic agitation; However, the Ni–P alloy deposit on NdFeB with ultrasonic agitation has the following advantages: uniform and smooth deposit grains, strong adhesion and good corrosion resistance.

Abstract: The upconversion luminescence nanocrystalline powders Y₂O ₃:Pr ³⁺ ,Yb ³⁺ were prepared by co-precipitation method and characterized by X－ray diffraction,fluorescence spectrum and so on. Its luminescence property and the effect of different calcining temperatures and rare-earth ion doped concentration on its luminescence property were discussed. The results show that the nanocrystalline powders calcined at 800-1200 °C for 2h has a single crystalline phase -the solid solution cubic system phase of Y₂O ₃. There is a upconversion luminescence phenomenon in the powders doped 1%(mol percent) Pr ³⁺ . The powders excited by a 980 nm laser diode emit weak green fluorescent observed by naked eye. The upconversion luminescence of Pr ³⁺in Y₂O ₃:Pr ³⁺ ,Yb ³⁺ is obviously different that of Pr3+in other materials.There are two stronger emission zone in upconversion emission spectra of the powders in the 400nm-800nm range,whose center wavelength value are respectively 551nm, 762nm.Increasing the calcining temperature of the samples from 1000°C to 1200°C, the emission peak intensity sharply elevates.

Abstract: As a great potential renewable energy source, solar energy is going to become one of the most important energies in the world. Recently, there has been an enormous increase in the understanding of the operational principle of PV tools, which led to a sudden increase in the power conversion efficiencies of such tools. Solar modules vary under temperature changes and the change in temperature will affect the output power modules. In this paper a relation between efficiency, sun radiation and temperature is used and under cloudy climate is simulated so we can obtain desired efficiency by adjusting temperature around PV module.

Abstract: ICMA and its derivatives, high performance acceptor of polymer solar cells, have received most attention in experimental and theoretical studies. In this work, we calculated electronic structures and spectroscopic properties of the ICMA by density functional theory (DFT) using B3LYP method. The geometrical structure data show that indene has little influence on C60. In comparison with [6,6]-phenyl C61-butyric acid methyl ester (PCBM), It was proved theoretically that ICMA possesses a better photovoltaic performance and higher LUMO energy level. ICMA and its derivatives could be a promising new acceptor which further improve the power conversion efficiency of the high performance polymer solar cells. The research indicates that the frontier molecular orbital are mainly localized on the C60 sphere, which shows carbon number of cage is an important factor leading to the change of optical and electrical properties. The present study provides theoretical supporting for further application of the ICMA and its derivatives in molecular design and structure-activity relationships research.

Abstract: By using generalized gradient approximation (GGA) scheme within the density functional theory (DFT), the electronic and magnetic properties of Hg₂CuTi-type Heusler alloy Ti₂FeAl were investigated. The results reveal that a 100% spin polarization appears at Fermi level (εF) in Ti₂FeAl, and is maintained during lattice range of 5.1Å~6.2Å. Ti₂FeAl is one of stable Half-Metallic Ferromagnets (HMF) with a spin-minority gap of 0.5 eV at εF and total magnetic moment of 1μB per unit cell. Our studies also indicate that the competition between RKKY-type indirect exchange and direct hybridization of d-electronic atoms plays a dominating role in determining the magnetism.

Abstract: In this work, the electronic and magnetic properties of Nb-doped full-Huesler alloy Ti2NiAl with Hg2CuTi-type structure have been investigated by using first-principles calculations within the density function theory (DFT). Due to the Nb which has less valence electrons than Ni doping into Ni-site, the gap around the Fermi level of the compound Ti2Ni1-xNbxAl (0≤x≤1) is gradually narrowed, and destroyed completely as x≥0.5. With the increase of x, it has gone through the transition from the ferromagnetism to the non-magnetism, and then to the ferromagnetism finally. Further analyses of density of states reveal that the d-electronic rehybridization induced by Nb-doping and RKKY-type indirect interaction is directly responsible for the changes of half-metallicity and magnetism.

Abstract: When the temperature is changed, due to the influence of the thermal expansion effect and thermo-optic effect, the thickness and refractive index of each layer of medium of photonic crystal will be Varied. As shown by optical resonators theory, the drift amount of the wavelength has a linear relationship with the variation of temperature. The electron beam lithography technology (EBL) and induction coupling plasma(ICP) etching were used for making the PCs with 1550nm central wavelength. An experiment mode is constructed for analyzing temperature characteristic of one-dimensional PCs, and then PCs is experimented at low temperature and high temperature. It can be found by experiment that, as the temperature changes, the central wavelength of photonic crystal has a linear relationship with the temperature, the drift amount of central wavelength at the low temperature is 0.072nm/°C,the drift amount at the high temperature is 0.076nm/°C,and the 3dB bandwidth of transmission spectrum of photonic crystal has no significant change, the spectral shape is changed very little.