基于脱硫反应的硫脲基罗丹明B 汞离子荧光化学剂量计的合成及分子氢键的影响

基于汞离子促进硫羰基脱硫的不可逆反应, 合成了两种分别含有丙烯酰基酰肼基硫脲基团和丙烯基酰肼基硫脲基团的罗丹明B 荧光探针(RhBHA 和RhBCH), 用以高选择性、高灵敏度检测水溶液中的Hg²⁺离子. 通过荧光发射光谱和可见光下颜色变化研究了硫羰基所处的化学环境对汞离子促进的脱硫反应的影响. 研究结果表明, 引入罗丹明B荧光生色团后, 分子的“开环-闭环”转换过程与分子内氢键作用没有相互影响, 分子内氢键加速了汞离子的脱硫反应,伴随“开环-闭环”转换过程的颜色变化通过肉眼即可观察到. 此外, 还研究了分子间氢键作用对脱硫反应速率的影响.通过加入汞离子后荧光强度随时间变化的跟踪发现, 若溶剂与RhBHA 形成分子间氢键作用, 会使汞离子诱导的脱硫反应有所迟缓. 这种分子间的氢键作用, 对能促进快速脱硫反应的分子内氢键作用产生影响.     

Effects of salt on solute association behavior in nanoconfined aqueous solutions

Using molecular dynamics simulations, we have studied the effects of salt on the association behavior of solute molecules in nanoconfined aqueous solutions. Three types of solute association states – dispersion, reversible and aggregation states – are still observed in nanoconfined aqueous solutions in the presence of salt. With the increase of ion concentration, the tendency toward the formation of larger clusters is enhanced and the solute critical aggregation number decreases. We even found the transformation of solute association state from the dispersion to the reversible state or from the reversible to the aggregation state within an intermediate range of solute number. This phenomenon is similar to the salting out process and is attributed to the decrease of free water molecules induced by the ion polarization.     

三维辐射无限元

提出三维点辐射和八结点无限元模型,以坐标原点为极点,或以一坐标轴为极轴,以球面或圆柱面为人工边界,以边界点的坐标和位移表示无限元内部任一点的坐标和位移.坐标映射函数和位移函数简单明了,并且能够方便地反映无限域内位移场的衰减特点.数值计算时只需对边界进行无限元的单元划分,无需基本解.算例结果表明,辐射无限元具有良好的精度.     

Simultaneous determination of urinary 31 metabolites of VOCs, 8-hydroxy-2′-deoxyguanosine,and trans-3′-hydroxycotinine by UPLC-MS/MS: 13C- and 15N-labeled isotoped internal standards are more effective on reduction of matrix effect

Analytical and Bioanalytical Chemistry - Human beings are inevitably exposed to volatile organic compounds (VOCs) of anthropogenic emissions as they are ubiquitous atmospheric pollutants. Smoking...     

Enrichment of large‐diameter semiconducting single‐walled carbon nanotubes by a mixed‐extractor strategy

In this work, we report a new mixed‐extractor strategy to improve the sorting yield of large‐diameter semiconducting single‐walled carbon nanotubes (s‐SWCNTs) with high purity. In the new mixed‐extractor strategy, two kinds of conjugated polymers with different rigidity, poly(9,9‐n‐dihexyl‐2,7‐fluorene‐alt‐9‐phenyl‐3,6‐carbazole) (PDFP) and poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (P8BT), are used to sort large‐diameter s‐SWCNTs through two simple sonication processes. To our surprise, although PDFP itself shows no selectivity toward s‐SWCNTs, it can greatly enhance the sorting yield of P8BT. Using the PDFP/P8BT mixed‐extractor method, the yield of sorted s‐SWCNTs has been enhanced by 5 times with a purity above 99 % in comparison to that using P8BT single‐extractor method. In addition, the photoluminescence (PL) excitation maps shows that the PDFP/P8BT mixed‐extractor system not only enhances the sorting yield substantially, but also tends to be enrichment of (15,4) SWCNTs with the diameter of 1.36 nm.     

刚体运动学的几何讨论

从几何的角度描述刚体的运动学. 刚体的几何描述对应着一个正交变换. 刚体的定轴转动对应着一个特征值为1的正交变换,相应的特征向量为刚体转动的定轴. 通过刚体定点转动的描述,简单地证明了有限转轴定理,并且给出了自由刚体运动的速度和位移公式.     

Janus Single-Layer CoClBr: A Direct Ferromagnetic Semiconductor with Controllable BandGap and Enhanced Magnetic Anisotropy Under Strain

The 2D materials with both ferromagnetism and semiconducting properties are desirable for spintronics applications. Here, inspired by the successful synthesis of single-layer CoCl ${}_2$, it predicts that Janus single-layer CoClBr is a 2D intrinsic ferromagnetic semiconductor with a direct bandgap of 3.71 eV by first-principles calculations. Single-layer CoClBr exhibits an in-plane magnetic anisotropic energy (MAE) of 542.25 $\mu$eV per Co atom and a Curie temperature (T ${}_c$) of 89.49 K. Biaxial strain can effectively modulate its bandgap, MAE, and T ${}_c$, but will not change the ferromagnetic ground state. Compressive strain can increase the Curie temperature and switch the spin moment from in-plane direction to out-of-plane direction. Tensile strain can enlarge the bandgap and introduce a direct-to-indirect bandgap transition in CoClBr. The MAE of CoClBr reaches 391.73 $\mu$eV per Co atom and 1560.49 $\mu$eV per Co atom at a compressive strain of -2% and a tensile strain of 5%, respectively. The tunable electronic and magnetic properties of Janus single-layer CoClBr has potential application in low-dimensional spintronics devices.     

Etched-Diffraction-Grating-Based Planar Waveguide Demultiplexer on Silicon-on-Insulator

An optical wavelength demultiplexer with the etched diffraction grating (EDG) on the silicon-on-insulator (SOI) material is demonstrated. Fabricated by the wet-anisotropic-etching method, 90° turning mirrors are used to bend waveguides, and the size of the EDG-based demultiplexer is minimized to only 16×2.5 mm². The crosstalk is below −16 dB. The on-chip loss is about 9.97 dB, which is composed of about 8.72 dB excess loss and 1.25 dB diffraction loss. The polarization-dependent central wavelength shift is below 0.13 nm, and the polarization-dependent loss is about 0.35 dB. The sources of the crosstalk and loss are discussed in details, and the related measures to improve the performance are also presented.     

模拟冲击波传播规律的自由拉氏法

 介绍了模拟可压缩流体运动规律的自由拉氏法，编制了一维程序，对激波管问题和飞片打靶问题进行了数值模拟，并将数值结果与传统拉氏方法的结果进行了比较。