Hole Burning and Fluorescence Spectra of Sol-Gel Derived Sm2+-Doped Glasses

Sm2+-doped glasses in the system of Al2O3-SiO2 were prepared by sol-gel processing of metal alkoxides and reacting with H2 gas at 800°C. The hole burning properties of these glasses were investigated. The holes were burned in the 7F0 5D0 line of the Sm2+ ions using a DCM dye laser at 77 K. The hole depth increased with increasing the laser irradiation time, reaching up to 15% of the total intensity within a few hundred seconds. The hole width was 3 cm–1 full width at half maximum. Fluorescence line narrowing spectra of the 5D0 7 F1 transition were analyzed to study the local structure surrounding the Sm2+ ion. It is concluded that the Sm2+ ions are closely coordinated with nine oxygens of the AlO6 group in aluminosilicate glasses and that the addition of Al3+ ions into glass induces an increase in the coordination number of the Sm2+.     

Epoxy-based azo molecular glasses with four-arm architecture: Preparation,characterization and holographic recording

A series of epoxy-based azo molecular glasses with four-arm architecture was synthesized, characterized and applied to holographic recording.     

CePO_4/Ce-ZrO_2可加工陶瓷性能与断裂机制研究

以Ce ZrO2为基体,通过复合不同加入量的第二相CePO4颗粒,研究了陶瓷材料力学性能的变化,并借助加载能谱仪(EDS)的扫描电子显微镜(SEM)对材料弯曲断口及压痕裂纹扩展方式进行分析。当CePO4加入量为25%时,虽然材料力学性能有一定下降,但已经能用WC刀具进行加工。材料的弯曲断口显示,CePO4在两相体系中的断裂呈层片状形式;加入CePO4后,由于两相之间弱结合界面的存在,压痕裂纹扩展形式发生明显变化,由连续扩展机制过渡为不连续扩展。由这两种机制形成的材料断裂过程是阶段性的,在实际中可以用作材料最终破坏前的预报。     

Microwave assisted low temperature synthesis of sodium zirconium phosphate (NaZr<Subscript>2</Subscript>P<Subscript>3</Subscript>O<Subscript>12</Subscript>)

Sodium zirconium phosphate [NaZr₂P₃O₁₂], a potential ceramic matrix for fixation of high level nuclear waste, was synthesized by heating the mixture of sodium carbonate [Na₂CO₃], zirconyl nitrate hydrate [ZrO(NO₃)₂·5H₂O] and ammonium dihydrogen phosphate [NH₄H₂PO₄] in air, in a resistance heated furnace and a microwave heating system respectively in the temperature range 450 to 650°C. The mixture heated for 1 h in a resistance furnace at 450°C yielded a poorly crystalline NaZr₂P₃O₁₂ [NZP]. Increasing the temperature to 650°C produced a highly crystalline product. The same mixture heated in a microwave oven at 450°C for 1 h however, yielded the most crystalline NZP.In an alternate method, the mixture of sodium dihydrogen phosphate (NaH₂PO₄), zirconium dioxide (ZrO₂) and diammonium hydrogen phosphate [(NH₄)₂HPO₄] heated in resistance furnace at 650°C for the same period did not react in air. It also did not yield the pure product at 450°C when heated in microwave assembly for 1 h.The authors thank the Board of Research in Nuclear Sciences (BRNS) of the Department of Atomic Energy (DAE) for the financial support for this work under the project No. 2000/37/19/BRNS/1959 dtd09-02-02.     

A DSC study of the effects of sugars on thermal properties of rice starch gels before and after aging

Thermal characterization of gelatinized binary rice starch-water and ternary starch-sugar-water gels before and after aging was carried out using differential scanning calorimetry. The glass transition temperature of the maximally freeze-concentrated solution (T_g) in both fresh and aged gels was observed to decrease progressively with increasing sugar concentration. Aging of the gels generally shiftedT_g to higher temperatures, but had little or no effect on the ice melting peak temperature (T _m). The presence of various sugars could either accelerate or retard starch (amylopectin) recrystallization, depending on the type and concentration of sugar, as well as on starch/water ratio. A hypothesis based on the dual antiplasticizing-plasticizing effects of sugars was postulated to explain the observed effects. Of the sugars studied, xylose and fructose appeared to display exceptional retardative and accelerative effects, respectively, on retrogradation.This study was funded by a Sixth Malaysia Plan R&D grant under the Intensification of Research Priority Areas (IRPA) Program of the Ministry of Science, Technology and Environment, Malaysia. We thank Dr. Harry Levine and Dr. Louise Slade for giving us the opportunity to contribute a paper to this special issue of JTA.     

一种非晶硅膜改性弹性玻璃毛细管交联中等极性固定相色谱柱的制备

研究了非晶硅膜改性的弹性玻璃毛细管交联ＯＶ－１７０１中等极性固定相色谱柱。在适当温度下，采用过氧化二异丙苯（ＤＣＵＰ）游离基引发交联ＯＶ－１７０１固定液，成功地制备了交联ＯＶ－１７０１柱，该柱具有柱效高、惰性好、耐溶剂、抗腐蚀和耐高温等性能，是一种新型高性能的中等极性交联柱。     

Glass capillary columns for separation of free organic acids

Glass capillary columns have been prepared without acidic additive in the stationary phase, from which free organic acids elute as sharp and symmetrical peaks. The required surface in the borosilicate glass capillary was generated by a combination of leaching with aqueous HCl and deposition of colloidal silica particles; it can be coated with stationary phases have a broad range of polarity. Aqueous samples containing free organic acids can also be analyzed in such columns in an isothermal mode.     

Preparation and Characterization of Nanotitanium Dioxide Coating Film Doped with Fe^3＋ Ions on Porous Ceramic

The nanotitanium dioxide （TiO2） photocatalytic and porous ceramic filtering technique is one of the advanced methods to effectively treat organic wastewater. The TiO2 sol doped with Fe^3＋ ions was prepared by sol-gel processing. The influences of the process conditions of coating nanophotocatalytic material- Fe^3＋-TiO2 film on the surface of porous ceramic filter by dipping-lift method on the performance of porous ceramic filter were studied. The porous ceramic filters have two functions at the same time, filtration and photocatalytic degradation. The results of this study showed that the pH and viscosity of the sol, amount of Fe^3＋ ions doped as well as the coating times greatly affect the quality of coating film, the performance parameters and the photocatalytic activity of the porous ceramic filter. When the pH of the sol is 3-4, the viscosity is about 6 mPa.S, the amount of doped Fe^3＋ ions is about 2.0 g/L, the porous ceramic filter has been shown to have the best filtering performance and photocatalytic activity. In this condition, the porosity of porous ceramic is about 42.5%, the pore diameter is 8-10μm. The degradation of methyl-orange is 74.76% under lighting for 120 rain.     

Effects of Poly(ethylene glycol) Doping on the Behavior of Pyrene, Rhodamine 6G, and Acrylodan-Labeled Bovine Serum Albumin Sequestered within Tetramethylorthosilane-Derived Sol-Gel-Processed Composites

We investigate the effects of controlled poly(ethylene glycol) (PEG) doping on the behavior of pyrene, rhodamine 6G (R6G), and acrylodan-labeled bovine serum albumin (BSA-Ac) sequestered within tetramethylorthosilicate (TMOS)-derived sol-gel-processed materials. To probe the dipolarity of the local environment within the composite we performed static fluorescence measurements on pyrene as the composites aged. We found that small levels of PEG loading effected significant enhancements in the local dipolarity surrounding the average pyrene molecule. Time-resolved fluorescence anisotropy measurements were used to follow the rotational reorientation dynamics of R6G as the composites aged. As the PEG loading increased, the R6G reorientational mobility increased. Nitrogen adsorption techniques were used to quantify the effects of PEG doping level on the surface area and final xerogel pore features. A large reduction in surface area was observed with PEG doping, but no detectable change in pore size was noted. The effects of PEG doping on a biomolecule were probed by following the time-resolved fluorescence anisotropy decay of BSA-Ac. These results showed that PEG doping resulted in increased biomolecule dynamics relative to that found for a neat, undoped TMOS-derived composites. Together these results show that PEG doping can be used to tune the sol-gel-processed composite dipolarity, alter the mobility of dopants sequestered within the composite, control analyte acessibility to the sensing chemistry, and modulate the internal dynamics within a biodopant.