激光二极管纵向抽运(Tm,Ho)∶YLF激光器的研究

对激光二极管端面抽运 (Tm ,Ho)∶YLF固体激光器的激光特性进行了研究。根据激光二极管抽运准三能级系统的特性 ,详尽地分析了能量在Tm3 + 离子和Ho3 + 离子之间的传递过程 ,给出了 (Tm ,Ho)∶YLF激光器准三能级的速率方程 ,对上转换及激光下能级粒子再吸收对激光二极管抽运 (Tm ,Ho)∶YLF激光器运转的影响进行了理论分析 ,得出了 (Tm ,Ho)∶YLF激光器的阈值抽运功率和斜率效率的解析表达式。同时对 (Tm ,Ho)∶YLF微片激光器的激光特性进行了实验研究 ,当保持晶体温度为 19℃时 ,阈值抽运功率为 4 2 5mW ,斜率效率为 2 2 .5 % ,最大光光转换效率为 17.4 % ,并且在将晶体保持在四个不同的温度下 ,给出了激光输出功率随抽运功率变化的实验结果。将理论与实验结果进行比较 ,发现吻合得比较好。     

Synthesis of 6-chloroquinolines using benzyltrimethylammonium tetrachloroiodate as a selective chlorinating agent and an efficient generator of HCl

Abstract  

A simple and efficient one-pot synthesis of 6-chloroquinolines was achieved in good yields via the three-component reaction of 2-aminoaryl ketones, α-methylene carbonyl compounds, and BTMA ICl₄ in AcOH.     

Electrosyntheses and characterization of poly(9-bromophenanthrene) in boron trifluoride diethyl etherate

A novel semi-conducting polymer poly(9-bromophenanthrene) (P9BP) was synthesized electrochemically by direct anodic oxidation of it is monomer 9-bromophenanthrene (9BP) in boron trifluoride diethyl etherate (BFEE). The oxidation onset potential of 9BP in this medium was measured to be only 1.33 V vs. saturated calomel electrode (SCE). P9BP films obtained from BFEE showed good electrochemical behavior and nice thermal stability with electrical conductivity of 0.03 S cm⁻¹. FTIR and ¹H NMR spectra together with theoretical quantum chemistry calculations indicated that the P9BP was mainly grown via the coupling of the monomer at C₃ and C₆ positions. Furthermore, P9BP exhibited strong electrochromic nature from opaque green to light yellow between the doped and dedoped states on ITO electrode in solid state. Fluorescence spectral studies indicated that P9BP was a blue light emitter.     

TiO2/Bi2O3纳米复合体的制备及可见光催化产氢性能

首先采用相分离的水解-溶剂热法制备了Bi₂O₃纳米粒子,然后利用简单的湿化学法在Bi₂O₃表面负载不同比例的TiO₂纳米颗粒,进而得到TiO₂/Bi₂O₃纳米复合体。通过气氛调控的表面光电压谱(SPS)等测试表明,表面负载适量的TiO₂后能够提高Bi₂O₃光生电荷分离。可见光催化产氢和降解污染物测试结果进一步证明,表面负载适量的TiO₂后可显著提高其可见光催化活性,其中Ti/Bi摩尔比为7%时具有最高的光催化活性。这主要归因于TiO₂具有较为合适的导带能级位置,可以接收Bi₂O₃在可见光激发下所产生的高能级电子,从而抑制光生电子-空穴对复合,并且维持了高能级电子较高的还原能力。     

氮掺杂石墨烯与g-C3N4二维异质体对纳米Fe2O3光催化剂的复合改性

使用相分离的水解-溶剂热法制备了α-Fe₂O₃纳米粒子, 通过简单的湿化学法实现了质量分数为3%的石墨烯、 氮掺杂石墨烯和g-C₃N₄ 3种二维异质体对纳米α-Fe₂O₃的复合改性, 并比较了3种二维异质体对α-Fe₂O₃光催化活性的影响. 结果表明, 在光催化还原二氧化碳和降解液相苯酚过程中, 二维异质体的复合均提高了纳米α-Fe₂O₃的光催化活性, 氮掺杂石墨烯对α-Fe₂O₃的改性效果优于石墨烯, 其中g-C₃N₄对α-Fe₂O₃的改性效果最优. 通过表面光电压谱、 光电化学及羟基自由基等测试, 确认二维异质体的复合改性主要通过促进纳米α-Fe₂O₃的光生电荷分离和提高活性中间组分(羟基自由基)的含量提高纳米α-Fe₂O₃的光催化活性.     

液相色谱-串联质谱法研究涕灭威及其代谢物在白菜中的动态行为

采用液相色谱-串联质谱法(LC-MS/MS)研究了白菜中涕灭威及其代谢物的残留动态行为。按农民常用施药量(3000 g/hm²)将涕灭威沟施予田地后,定期取样检测,并建立其残留行为的数学模型。结果表明,用LC-MS/MS测定涕灭威及其代谢物,在0.005~0.2 mg/L范围内线性关系良好,平均回收率为78.9%~108.5%,相对标准偏差为2.03%~8.91%(n=8)。涕灭威在白菜中的浓度升高和降低的过程均符合一级动力学模型(c=0.020e^0.136t和c=0.65e^-0.059t),相关系数(r²)分别为0.888和0.979,半衰期为29.1天。代谢产物涕灭威砜和涕灭威亚砜在白菜中的浓度降低时同样符合一级动力学方程(c=23.4e^-0.044t和c=4.54e^-0.027t), r²分别为0.916和0.972。涕灭威、涕灭威砜和涕灭威亚砜在白菜中的含量要降到国内外限量要求0.01 mg/kg,分别需要70.7、226.6和176.3天。白菜生长周期为120天,收获时涕灭威砜和涕灭威亚砜含量仍超过国内外限量要求。因此,在本文施药量下,涕灭威不能使用。该数据为涕灭威的安全使用和农药残留动态行为研究提供了理论依据。     

Synthesis of large surface area LaFeO3 nanoparticles by SBA-16 template method as high active visible photocatalysts

Nanosized LaFeO₃ with large specific surface area has been successfully synthesized by an impregnation process, with mesoporous silica SBA-16 as hard template and corresponding metal nitrates as La and Fe resources, and the resulting LaFeO₃ is also characterized by thermogravimetry–differential thermal analysis (TG–DTA), X-ray diffraction (XRD), N₂ adsorption–desorptions, Brunauer Emmett Teller (BET) technique, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflection spectrum (UV–Vis DRS), and surface photovoltage spectroscopy (SPS). It is found that, compared with that prepared by the conventional citrate method, the as-prepared LaFeO₃ with 20-50 nm particle size has remarkable large specific surface area, even still with the surface area as large as about 85 m² g⁻¹ after calcination at 800 °C, which is attributed to its mesoporous structure as well as the small particle size. During the photocatalytic degradation of Rhodamine B solution under visible irradiation, all the LaFeO₃ samples obtained are superior to P25 TiO₂, and the activity becomes high with increasing calcination temperature. It is revealed that the excellent photocatalytic performance is mainly ascribed to the large surface area and high photogenerated charge separation rate.     

XUV pulse effect on signal modulations of harmonic spectra from H$$_{2}^{+}$$ and T$$_{2}^{+}$$

The effects of signal modulations on the molecular high-order harmonic generations in \(\hbox {H}_{2}^{+ }\) and \(\hbox {T}_{2}^{+}\) have been theoretically investigated. It is found that with the introduction of the XUV pulse, due to the absorption of the extra XUV photons in the recombination process, multiplateaus on the harmonic spectra, separated by the XUV photon energy can be found. Moreover, this multiplateau structure is insensitive to the wavelength of the XUV pulse. In shorter pulse duration, the intensities of the multiplateaus from \(\hbox {H}_{2}^{+}\) are higher than those from \(\hbox {T}_{2}^{+}\); while in longer pulse duration, the opposite results can be found. Finally, by changing the delay time of the XUV pulse, the signal modulations (including the amplitude and the frequency modulations) of the multiplateaus can be controlled.     

Au Nanoparticles Loaded on Hollow TiO2 Microspheres with (001) Exposed Facets: a Strategy for Promoting Photocatalytic Performance

Au nanoparticles loaded TiO₂ hollow microspheres with exposed (001) facets(Au-HTFs) were synthesized through template-free hydrothermal process combined with a chemical reduction role. Au-HTFs displayed excellent photocatalytic activity in catalyzing oxidization reaction in organic pollutant system, which originates from the synergistic effect of the reactive (001) facets and Au nanoparticles with a wide range of absorption in visible region based on localized surface plasmon resonance effect. The unique synergistic effect could largely increase the photocatalytic performance resulting from the improvements of both the visible light aborption and the recombination of electron-hole pairs. Our findings revealed that among Au-HTFs with different Au loading percentages, Au-HTFs with 2%(mass fraction) Au loading possessed the superior photocatalytic activity.