Slow Light Effect and Multimode Lasing in a Photonic Crystal Waveguide Microlaser

The slow light effect in a photonic crystal waveguide is investigated theoretically and experimentally. Theoretical calculation indicates that there is a slow light region for the even mode, from which the resonance and lasing in a microcavity would benefit. A photonic crystal waveguide microlaser is fabricated, which is related to the group velocity of c/120.6.     

Assessing the authenticity of commercial deep-sea drinking water by chemical and isotopic approaches

This study combines stable isotopes and chemical elements with statistical principal component analysis (PCA) to assess the authenticity of bottled commercial drinking water desalinized from deep seawater in the Taiwan market. Isotopic results indicate that true bottled deep-sea drinking water (DSDW) exhibits about 0?‰ for both δ²H and δ¹⁸O values, which are values similar to those of open seawater. By comparison, suspected counterfeit DSDW products display δ²H and δ¹⁸O values of around ?51?‰ and ?8?‰, respectively. These values are representative of terrestrial freshwater. In addition, suspected counterfeit DSDWs have δ and electrical conductivity values similar to a mixed water (MW) product that was manufactured by purifying terrestrial freshwater and adulterating this with small amounts of brine. Furthermore, PCA results indicate the chemical constitution of suspected DSDW products to be similar to the MW product which falls between purified terrestrial freshwater and desalinized open seawater. These similarities imply that suspected counterfeit DSDW products are manufactured in a similar manner to the declared MW product. This study demonstrates how combining knowledge of stable water isotopes and PCA can be used in assessing the authenticity of commercial DSDW products. The method should be of great interest to similar investigations elsewhere.     

Gd2(WO4)3: Eu纳米发光材料中黄昆因子和能量传递速率的实验获得

采用共沉淀法制备了不同Eu³⁺掺杂浓度的Gd₂(WO₄)₃纳米发光材料. 测量了纳米材料样品的X射线衍射谱(XRD) 和场发射扫描电镜, 对样品的结构和形貌进行了表征. 测量了各样品的发射光谱和激发光谱(声子边带光谱), 绘制了浓度猝灭曲线, 确定了最佳的掺杂浓度为20 mol%. 通过声子边带光谱计算了不同掺杂浓度样品的黄昆因子. 测量了不同浓度样品的荧光寿命, 利用Auzel模型对Eu^{3+ 5}D₀能级荧光寿命数据进行了拟合, 确定了⁵D₀能级的固有寿命和猝灭过程中生成的声子数. 本文还根据荧光寿命数据计算了Eu³⁺之间的能量传递速率, 确定了能量传递速率与浓度的关系. 关键词： 钨酸盐 3+')" href="#">Eu³⁺ 黄昆因子 能量传递速率     

时域飞秒散斑的特性与测量

阐述了飞秒激光脉冲在随机介质传播过程中产生时域散斑的原理,并对时域飞秒散斑进行了测量. 时域飞秒散斑的产生是飞秒脉冲在随机介质中经历多重散射形成的随机干涉现象在时域的体现. 初步讨论了时域散斑的统计特性并给出了相应的实验结果. 关键词： 时域散斑 飞秒脉冲 随机介质     

Visible-light-mediated external-reductant-free reductive cross coupling of benzylammonium salts with (hetero)aryl nitriles

Herein we report a novel visible-light-mediated external reductant-free reductive cross coupling for the construction of C sp~2–C sp~3 bonds. A variety of benzylammonium salts underwent selective coupling with(hetero)aryl nitriles to deliver important diarylmethanes under mild reaction conditions. Importantly, photocatalysts can be omitted for many cases, which might involve the electron donor acceptor(EDA) complex. Mechanistic studies indicated benzylic radicals might be involved as the key intermediates. Moreover, the in situ generated NMe_3 via cleavage of C–N bond in ammonium salts acts as the electron donor,thus avoiding the use of external-reductant.     

Ligusaginoids A–D,four eremophilane-type sesquiterpenoid dimers and trimers from Ligularia sagitta

Four novel highly oxygenated eremophilane-type sesquiterpenoid dimers and trimers with the unique 6/6/5/5 polycyclic skeleton, designated as ligusaginoids A–D (1–4), were isolated from the aerial parts of Ligularia sagitta. Their structures with absolute configurations were determined by a combined method. Moreover, a plausible biosynthetic pathway of 1–4 was also proposed. These compounds showed weak antibacterial activities.     

Shape-persistent elliptic macrocycles composed of polycyclic aromatic hydrocarbons: synthesis and photophysical properties

Bimolecular coupling/unimolecular cyclization strategies, including McMurry- and Glaser-type homocoupling reactions, were utilized to synthesize two shape-persistent elliptic macrocycles, which consist of polycyclic aromatic hydrocarbon units. The identity and purity of both macrocycles MC1 and MC2 were verified by 1H and 13C NMR, elemental analysis, as well as MALDI-TOF MS. The photophysical properties of MC1 and MC2 in dilute solution were also investigated.     

硼、磷共掺杂铁钴双金属材料的制备及其电催化析氧性能

采用一步水热法合成了硼、磷共掺杂铁钴材料(Fe-Co-B-P)。借助扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)等技术对所合成材料的形貌、结构和组成进行表征。利用线性扫描伏安(LSV)、循环伏安(CV)、电化学阻抗谱(EIS)等技术研究材料电化学析氧反应(OER)性能。结果表明,Fe-Co-B-P表面疏松且粗糙,颗粒间有许多空隙。在电流密度为10和100 mA·cm^-2时,其过电势分别为278和309 mV,Tafel斜率为24 mV·dec^-1,说明该材料具有较优的电催化析氧性能。其在连续进行10 h的计时电位测试过程中,电势基本保持在1.55 V(vs RHE),表明该催化剂具有较好的电化学稳定性。这是由于铁钴双金属与硼、磷非金属之间的协同作用促进了电子的传递。     

含有AlGaAs插入层的InAs/GaAs三色量子点红外探测器

本文报道了采用分子束外延技术制备的三色InAs/GaAs量子点红外探测器. 器件采用nin型结构, 吸收区结构是在InGaAs量子阱中生长含有AlGaAs插入层的InAs量子点, 器件在77 K下的红外光电流谱有三个峰值: 6.3, 10.2和11 μm. 文中分析了它们的跃迁机制, 并且分别进行了指认. 因为有源区采用了不对称结构, 所以器件在外加偏压正负方向不同时, 光电流谱峰值的强度存在一些差异. 不论在正偏压或者负偏压下, 当偏压达到较高值, 再进一步增大偏压时, 都出现了对应于连续态的跃迁峰强度明显下降的现象, 这是由量子点基态与阱外连续态的波函数交叠随着偏压进一步增大而迅速减小导致的.