痕量磷化氢的冷阱二次富集机理与GC/FID分析方法研究

将火焰离子化检测器(FID)应用于二次富集气相色谱检测中构建了冷阱二次富集-GC/FID系统检测环境中痕量磷化氢的分析方法。研究了冷阱温度、载气流量、柱温箱温度和检测器温度对该系统富集检测效果的影响,讨论了磷化氢富集的机理,并将该系统应用于广州地区典型水稻田环境中结合态磷化氢(MBP)的检测。结果表明:当冷阱温度为-90℃,载气流量为1.5 mL/min,柱温箱温度为90℃,检测器温度为220℃时,系统操作条件最优。冷阱二次富集磷化氢的主要机理是富集毛细管柱(KB-Al2O3/NaSO4)对磷化氢的吸附作用,属气-固吸附。系统检出限为0.041 7 pg,精密度为4.3%。整个水稻生长周期内,水稻土中结合态磷化氢(MBP)的平均含量为120.59 ng/kg,测定结果的相对标准偏差均值为8.5%。该方法对痕量磷化氢的检测效果与使用氮磷检测器(NPD)的传统方法相近,但FID检测器的结构简单、操作方便、价格经济,使环境中痕量磷化氢的检测更容易实现,可推广应用。     

In-plane optical anisotropy of two-dimensional VOCl single crystal with weak interlayer interaction

Transition-metal oxyhalides $MOX$ ($M = {\rm Fe}$, Cr, V; $O ={\rm oxygen}$, $X= {\rm F}$, Cl, Br, I), an emerging type of two-dimensional (2D) van der Waals materials, have been both theoretically and experimentally demonstrated to possess unique electronic and magnetic properties. However, the intrinsic in-plane anisotropic properties of 2D VOCl still lacks in-depth research, especially optical anisotropy. Herein, a systematic Raman spectroscopic study is performed on VOCl single-crystal with different incident laser polarization at various temperatures. The polarized-dependent Raman scattering spectra reveal that the ${{ A}}_{{\rm g}}$ mode of VOCl show a 2-lobed shape in parallel polarization configuration while a 4-lobed shape in vertical configuration. In addition, the temperature-dependent and thickness-dependent Raman scattering spectra confirm a relatively weak van der Waals interaction between each layers among VOCl single crystal. These findings might provide better understanding on the in-plane anisotropic phenomenon in VOCl layers, thus will accelate further application of 2D single crystals for nanoscale angle-dependent optoelectronics.     

Scattering Noise Properties of Holographic Photopolymers by Means of Real-Time Transmittance Analysis

We propose a simplified model to analyse the temporary behaviour of transmittance for holographic photopolyreefs, based on the existing first-harmonic diffusion theory, with assumptions of constant polymerization coefficient and negligible diffusion effect for noise gratings. By applying this model to measure real-fime transmittance of our novel blue-sensitized photopolymer, the bleaching time constant of dye and polymerization rate are extracted, and the effect of the material composite on the noise property is revealed. This provides a prompt method to assess the performances of holographic photopolymers.     

阴离子化合物Y5Si3衬底增强石墨烯氧还原反应的第一性原理研究

本文采用阴离子化合物Y₅Si₃作为衬底,可以和石墨烯组成有效的氧还原催化剂. 反应热计算结果表明,阴离子材料可以促进氧还原反应中的决速步-氧气质子化的过程,从而增强石墨烯的氧还原能力. 电子结构计算表明体系较低的功函数(3.5 eV),良好的导电性以及从衬底到石墨烯的电荷转移都可以促进石墨烯的氧还原催化能力.     

增益饱和反射型量子点半导体光放大器高通特性

反射型量子点半导体光放大器(R-QDSOA)相较于传统RSOA具有皮秒级的载流子恢复速率和几十GHz的调制带宽,将其应用在高速的波分复用无源光网络(WDM-PON)中具有巨大的潜力.根据R-QDOSA的载流子速率方程和光场传输方程,建立了R-QDSOA的仿真模型,对其在增益饱和情况下的高通特性进行研究.研究结果表明:通过增加输入光功率、最大模式增益、有源区长度和减小注入电流,可提高最大信号增益和3dB截止频率;通过合理的参数设置,R-QDSOA的3dB截止频率可高达10GHz以上.该研究在无色WDM-PON的再调制方面展现了巨大的优势,并对提高R-QDSOA调制带宽具有理论指导意义.     

乙酰化呋喃型糖基三唑羧酸酯及硫苷的立体选择性合成

自从发现糖酯及硫苷类化合物具有抗菌、抗肿瘤等广泛的生理活性以来,有关这两类化合物的合成及其性质研究已成为人们极为关注的课题。但具有某些生理活性的三唑羧酸类和巯基嘧啶类化合物与糖基形成糖酯和硫苷的有关合成尚未见文献报道。为了寻找高效低毒的化合物,本文通过相转移催化法,在温和的反应条件下,立体专一性地合成了吡喃型     

概率统计中的“直觉-逻辑-仿真”闭环教学法

在概率论与数理统计授课中,学员的直觉常常与课程结果发生冲突.应对该问题,本文设计了“直觉判断-逻辑推理-仿真验证”的层层递进和回路闭环的教学方法,借助问卷调查引导学员融入博弈角色,将抽象的理论变成易于理解的案例和视觉直观的图像.教学实践表明,闭环教学法能够帮助学员化解本课程的学习困难,进而提高学员的实践能力.该方法的教学效果在多个教学班和多次教学大赛中得到验证,值得推广.