Advanced Materials Research Vols. 399-401

Abstract: We study the resonant tunneling in symmetric GaAs/Al_xGa_1-xAs/In_yGa_1-yAs double-barrier resonant-tunneling structures. Effects of three factors on the resonant tunneling are simulated and discussed. On increasing the barrier height, the decrease of current density is attributed to the interplay between the increase of the supply function of available electrons and the rapid decrease of the transmission coefficient through the device area, and the lowest Indium content for realizing the zero-bias resonant tunneling increases. With the increase of the barrier (well) width, the decrease of the current density can be explained by the fact that both the supply function and the transmission coefficient decreases, and the lowest Indium content meeting the zero-bias resonant condition decreases.

Abstract: Ordered molecular assemblies of novel sandwich-type heteroleptic (porphyrinato) (phthalocyaninato) europium complex (a double-decker compound) molecules were fabricated by Langmuir–Blodgett technique. The monolayer behaviors of the complex molecules were investigated using a series of techniques including surface pressure-area isotherm measurement, UV-vis spectroscopy, polarized UV-vis spectroscopy, and low-angle X-ray diffractometry. The results indicated that double-decker complex molecules form well-ordered and stable monolayers with a face-to-face configuration and edge-on arrangement to the water surface at the air-water interface as well as J-aggregates in lamellar multilayers on solid substrates. The orientation angle of the macrocycle in the double-decker compound with respect to the quartz slice surface in the LB films have been determined on the basis of the polarized absorbance and were found to be ca. 42^o.

Abstract: Nd₅Fe₉₂B₃ alloy was induction-melted. The α-Fe compounded low content of Nd₂Fe₁₄B nanocomposites were prepared using a melt-spinning method, subsequent annealing treatment, and ball milling. The complex permittivity, permeability of composites was measured in the 0.5-18 GHz frequency range. The permeability spectra exhibits relaxation type characteristic. The α-Fe/Nd₂Fe₁₄B composites shows an excellent microwave absorption property (reflection loss: RL<-20dB) in 9-17GHz with thin matching thickness 1.6-2.5 mm, due to the cooperate effect of magnetic loss and dielectric loss. α-Fe/Nd₂Fe₁₄B nanocomposites are thought to be a good microwave absorbers in GHz microwave range.

Abstract: A new unsymmetrical photochromic diarylethene compound, 1-[(2-methyl-5-(4-dioxolane-phenyl)-3-thienyl)]-2-(5-cyano-1,5-dimethyl-4-pyrryl)perfluorocyclopentene (1o), was synthesized and its photochemical, fluorescence properties were investigated in detail both in solution and PMMA amorphous film. The results showed that the compound exhibited remarkable photochromism, changing from colorless to violet after irradiation with 297 nm UV light. Finally, using this diarylethene as recording medium, polarization optical recording was carried out successfully.

Abstract: Poly (ethylene-co-tetrafluoroethylene) (ETFE) membranes were irradiated by electron beams and then acrylic acid (AA) and sodium styrene sulfonate (SSS) were grafted onto the membranes, in an attempt to prepare cation exchange membranes containing -COOH and -SO₃Na groups. The grafting yield was found to be strongly dependent on the synthesis condition such as irradiation dose, co-monomer composition. Infrared spectroscopy of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups. The membrane resistance decreases with the increasing of grafting yield

Abstract: A new asymmetric photochromic diarylethene bearing a benzofuran unit was synthesized, namely [1-(2-methyl-3-benzofuranyl)-2-(2-methoxyphenyl)]perfluorocyclopentene (1o). Its photochromic and fluorescent properties were investigated, respectively. The compound exhibited reversible photochromism, changing from colorless to red upon irradiation with UV light both in solution and in PMMA film. The diarylethene exhibited relatively strong fluorescence at 410 nm in hexane solution and 462 nm in PMMA amorphous film when excited at 300 and 385 nm, respectively. The fluorescence intensity decreased along with the photochromism both in hexane and PMMA film upon irradiation with 297 nm light.

Abstract: A new unsymmetrical photochromic diarylethene, 1-(2,4-dimethyl-3-isoxazol)-2-[2-methyl-5-(3- formyl-4- methoxyl)-3-thienyl]perfluorocyclopentene (1a) was synthesized, its photochromic properties were examined, the result indicated that the Diarylethene 1a changed the color from colorless to purple upon irradiation with 297 nm UV light, in which absorption maxima were observed at 538 and 541 nm in methanol and PMMA film, respectively. In methanol solution, the open-ring isomer of the diarylethene 1 exhibited relatively fluorescence at 501 nm when excited at 305 nm.

Abstract: A review is provided of the research progress of silica modified with vinyltriethoxysilane (VTES-SiO₂). The typical methods for preparing VTES-SiO₂ are introduced. The structure and stability of VTES layer and the controllability of various modified methods are elucidated. The characterization of VTES modified layer by means of Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, nuclear magnetic resonance, thermogravimetry, scanning electron microscopy and transmission electron microscopy are highlighted. Moreover, the application of VTES-SiO2 in the fields of rubber, glass, china, fiber, leather, paint, drug carrier, luminescent materials, catalyst technology, analytical chemistry and biochemistry were described in detail. The development trend on the preparation, determination of active groups and applications for VTES-SiO₂ were prospected, as well as the mechanism and the existing problems.

Abstract: New red phosphorescent material, (E)-2-(2-(thiophen-2-yl) vinyl)benzothiazole(2THSBT) iridium(III) acetylacetone(acac) complex [(2THSBT)₂Ir(acac)] is synthesized from 2-methyl benzothiazole, thiophene-2-carbaldehyde and iridium trichloride anhydrate. The complex is characterized by MS and 1H-NMR. (2THSBT)₂Ir(acac) gives a photoluminescence at 687nm, phosphorescent quantum yield: Φ_{(2THSBT)2Ir(acac)}=0.2 and EHOMO = -4.8 eV, ELUMO = -2.6eV, respectively. The complex may be a promising electrophosphorescent material.

Abstract: Magnetic microspheres with chitosan (CTS) and nano-iron (NI) as materials were synthesized by reverse suspension polymerization technology, and then modified with ethylenediamine (EDA). The average amine content of as-prepared magnetic microspheres (CTS-NI-MM-EDA) is 5.22 mmol/g, and the iron content is 23.77%.The adsorption experiments indicated that the adsorption rate of CTS-NI-MM-EDA for methyl orange is in the range of 62%-86% when the concentration of methyl orange is less than 250 mg/L, and the saturated adsorption quantity is 1651mg/g at 25 oC and pH 5.5.