Proton- and redox-controlled switching of photo- and electrochemiluminescence in thiophenyl-substituted boron-dipyrromethene dyes

A luminescent molecular switch in which the active thiol/disulfide switching element is attached to a meso-phenyl-substituted boron-dipyrromethene (BDP) chromophore as the signalling unit is presented. The combination of these two functional units offers great versatility for multimodal switching of luminescence: 1) deprotonation/protonation of the thiol/thiolate moiety allows the highly fluorescent meso-p-thiophenol-BDP and its nonfluorescent thiolate analogue to be chemically and reversibly interconverted, 2) electrochemical oxidation of the monomeric dyes yields the fluorescent disulfide-bridged bichromophoric dimer, also in a fully reversible process, and 3) besides conventional photoexcitation, the well separated redox potentials of the BDP also allow the excited BDP state to be generated electrochemically (i.e., processes 1) and 2) can be employed to control both photo- and electrochemiluminescence (ECL) of the BDP). The paper introduces and characterizes the various states of the switch and discusses the underlying mechanisms. Investigation of the ortho analogue of the dimer provided insight into potential chromophore-chromophore interactions in such bichromophoric architectures in both the ground and the excited state. Comparison of the optical and redox properties of the two disulfide dimers further revealed structural requirements both for redox switches and for ECL-active molecular ensembles. By employing thiol/disulfide switching chemistry and BDP luminescence features, it was possible to create a prototype molecular ensemble that shows both fully reversible proton- and redox-gated electrochemiluminescence.     

pK(a) Switching induced by the change in the pi-conjugated system based on photochromism

Two diarylethene derivatives 1 a and 2 a containing a 2,5-diaryl-3-thienyl group have been designed and synthesized. The pK(a) values of these compounds change upon photoirradiation. They have a phenol group as a proton source and a pyridinium group as an acceptor unit at each end of the pi-conjugated chain. The cyclization/cycloreversion reactions can be used to control the length of the pi-conjugated chain between the proton source and the acceptor. The change in the pi-conjugated chain length caused the pK(a)-switching.     

Tautocrowns: a concept for a sensing molecule with an active side-arm

A new sensing molecule containing aza-15-crown-5 as a receptor and 4-(phenyldiazenyl)naphthalen-1-ol as a signal converter has been synthesized. In the free ligand, the hydrogen bonding between the tautomeric OH group and the nitrogen atom from the macrocycle fully shifts the tautomeric equilibrium towards the enol form. The complexation reverses the equilibrium as a result of the strong interaction between the metal ion captured in the macrocyclic moiety and the tautomeric carbonyl group. The complex formation is accompanied by strong bathochromic (between 60 and 100 nm) and hyperchromic effects on the absorption spectra. Obviously, the tautomeric OH/CO groups play the role of an active side-arm in the complexation, supporting it via formation of a 3D cavity and giving possibility for ejection of the guest compound under stimuli to shift the tautomeric process back.     

Modulating Large‐Area Self‐Assembly at the Solid–Liquid Interface by pH‐Mediated Conformational Switching

Dynamic surfaces : The conformational transition of 2,6‐bis(1‐aryl‐1,2,3‐triazol‐4‐yl)pyridine (BTP) derivatives, triggered by a change in pH, has been observed with a sub‐nm resolution by STM at the solid–liquid interface. Upon addition of trifluoroacetic acid two different BTP molecules, each forming a highly ordered physisorbed monolayer, underwent significant conformational changes from their “rosette” to their “tetragon” forms, as reflected in dramatically altered 2D self‐assembly over large areas extending over hundreds of nanometers (see graphic).

     

模块化低阻抗紧凑型Marx发生器

设计的10级低阻抗紧凑型Marx发生器整体体积约0.12 m3,输出功率为30 GW,脉宽200 ns。该发生器采用正负充电,触发开关为三电极场畸变开关,其余开关采用过压自击穿开关;经优化设计,自击穿开关高33 mm、电感13.1 nH,触发开关高42 mm、电感15.2 nH。电容正负电极片与开关电极采用挤压连接,电极片间绝缘材料为聚丙烯薄膜,薄膜共100层,总厚度2 mm,耐受电压大于100 kV;Maxwell模拟表明:此种连接方式可将每个电极连接片电感降低到4.16 nH。Pspice电路模拟和实验均表明:电容器充电100 kV条件下,12 负载上可获得电压高于600 kV、峰值电流大于50 kA的输出。     

快脉冲直线变压器气体开关技术

阐述了Z箍缩驱动惯性聚变装置对快脉冲直线变压器气体开关的需求背景,介绍了快脉冲直线变压器气体开关技术发展的基本要求及国际研究进展,归纳了近年来主要研究成果和对当前研究有重要借鉴意义的结论,给出了提高静态稳定性、降低触发阈值和延长开关寿命的措施。介绍了气体放电的汤逊和流注理论,指出:在不大于1.5106 Pacm范围内,汤逊理论完全适用于描述气体开关自击穿过程。根据巴申定律、Meek击穿判据,给出了开关气压和间距设计要点,分析了多间隙开关间隙数量和间隙的电压分布均匀性对开关自击穿电压的影响。根据触发击穿延时经验公式,归纳了降低触发电压阈值的技术途径。介绍了1维的电极熔蚀判据,并总结了减轻电极烧蚀的方法和措施最后指出开关技术研究总体策略和方法。     

光敏异构化智能生物开关的进展

引出光敏异构化智能生物开关的概念。介绍了可逆光敏异构化生物物质的机制和特点, 并结合这个领域的研究和发展对其进行了较全面的讨论。探讨了可逆异构化开关物质在光记忆、电化学控制、生物传感器等方面的应用, 并对它的未来前景作出展望。     

XH-1装置电感储能系统的电路模拟

 针对XH-1装置电感储能系统,建立了电爆炸断路开关基于开关电阻倍增比与比能关系的电路模型,给出了与电感储能系统耦合时,利用PSPICE模拟计算得到的开关上的电流电压波形和负载上的电压波形,分析了负载阻抗参数对输出脉冲的影响。