Preparation and optical properties of Ag/PPy composite colloids

Ag/PPy (polypyrrole) composite colloids were prepared through the reaction of silver nitrate with pyrrole solution in DNIF either in the dark, or under the irradiation of femtosecond laser (fs) pulse or UV lamp. The UV-vis spectra of the nanocomposite colloid display an intense absorption band around 620 nm, accompanied by a weak one around 470 nm. The colors and optical absorption spectra of as-synthesized colloids can be reversibly tuned between blue and red, corresponding to absorption band of 620 urn and 526 urn, within few seconds by adding base and acid solutions or gases in turn into the composite colloid suspension. In addition, excess of H+ solution enhanced the absorption band around 470 nm and, at the same time, depressed that around 620 nm. The possible mechanism for the formation and optical absorption properties of the Ag/PPy composite colloid was proposed. (C) 2006 Elsevier B.V. All rights reserved.

Frequency upconversion fluorescence emission of Er3+-doped oxychloride germanate glass

Frequency upconversion fluorescence property of Er3+-doped oxychloride germanate glass is investigated. Intense green and red emissions centred at 525, 546, and 657nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> 4I(15/2), and F-4(9/2) -> I-4(15/2), respectively, were simultaneously observed at room temperature. The quadratic dependence of the 525, 546, and 657nm emissions on excitation power indicates that a two-photon absorption process occurs under 975nm laser diode (LD) excitation. The Raman spectrum investigation indicates that oxychloride germanate glass has the maximum phonon energy at similar to 805 cm(-1). The thermal stability of this oxychloride germanate glass is evaluated by differential scanning calorimetry, and thermal stability factor Delta T (Delta T = T-x-T-g) is 187 degrees C. Intense upconversion luminescence and good thermal stability indicate that Er3+-doped oxychloride germanate glass is a promising upconversion laser material.

硼对植物生殖器官建成的作用

实验以黄瓜植物为材料，研究了硼在个体水平上和器官水平上对植物生殖器官建成的作用，并用放射性同位素示踪法研究了硼对植物生殖器官的作用同植物体内糖运输的关系。结果表明，在个体水平上，缺硼使植物体上雄花和雌花数目都减少，但缺硼对雌花形成和雄花形成的影响并不相同，缺硼使植物体上形成较多的雄花，较少的雌花。在器官水平上，硼的作用同它的浓度有关，在某一浓度范围内，缺硼不利于黄瓜花蕾发育成雌花-也不利于雄花花药的发育;硼浓度的升高有利于花蕾发育成雌花，也有利于发育成雄花的花蕾花药的发育。较高浓度的硼则明显使黄瓜花蕾不易发育成雌花，但有利于发育成雄花的花蕾花药的发育。在个体水平上，缺硼对生殖器官建成的作用同花蕾组织中可溶性糖的缺乏有关，这可能是由于缺硼抑制了茎等输导组织的糖吸收活动而使叶片光合作用所合成的糖不易运到花蕾中的原因。