Enhanced Electrochemical Performance of Hybrid Solid Polymer Electrolytes Encompassing Viologen for All-Solid-State Lithium Polymer Batteries

Hybrid solid polymer electrolytes (HSPE) comprising poly(ethyleneoxide) (PEO), LiTFSI, barium titanate (BaTiO3), and viologenare prepared by a facile hot press. The physical properties of theHSPE membranes are studied by using small-angle and wide-angle X-rayscattering, thermogravimetric analysis, differential scanning calorimetry,and tensile strength. The prepared hybrid solid polymer electrolytesare also investigated by means of ionic conductivity and transportnumber measurements. The employed analyses collectively reveal thateach additive in the PEO host contributes to a specific property:LiTFSI is essential in providing ionic species, while BaTiO3 and viologen enhance the thermal stability, ionic conductivity,and transport number. The enhanced value in the Li+-transportnumber of HSPE are presumably attributed to the electrostatic attractionof TFSI anions and the positive charges of viologen. Synergistically,the added BaTiO3 and viologen improve the electrochemicalproperties of HSPE for the applications in all-solid-state-lithiumpolymer batteries

Observation of inhomogeneous plasmonic field distribution in a nanocavity

等离激元材料和器件中电场的强度分布是等离激元技术及其应用的重要基础。虽然针尖增强光谱成像技术的发展已经实现了亚纳米的横向空间分辨率，并发现了亚纳米级电场的不均匀性，但是迄今人们对电场的纵向场强分布仍然知之甚少。李剑锋教授课题组设计了一种具有~2Å空间分辨率的分子尺，利用金单晶基底和壳层隔绝金纳米粒子来构筑等离激元纳米腔，并通过分子尺的拉曼信号强度，精准地直接表征纳米腔中的纵轴方向上高度不均匀的场强分布。中国科学技术大学罗毅教授课题组利用基于量子场论的局域场光谱理论，精确地模拟得到了与实验相符的等离激元纳腔中的场分布，并发现了因分子自聚焦作用而引起的“等离激元梳”。该工作提供了一种通用有效的定量表征纳腔中场强分布的方法，完善了对等离激元学基础的理解，为超高空间分辨的拉曼光谱成像、光学力调控分子组装、单分子反应操控提供指导。 该工作是在李剑锋教授和中国科学技术大学罗毅教授共同指导下完成的。实验部分主要由李超禹（论文第一作者，已毕业博士）、温宝英（在读博士）、李松波（已毕业硕士）完成，复旦大学段赛研究员（论文共同第一作者）和陈舒（已毕业博士）进行了局域场光谱理论计算。谢立强（已毕业博士）和毛秉伟教授帮助完成了扫描探针显微镜实验。浙江师范大学周小顺教授和王亚浩老师提供了自组装膜表征方面的重要帮助。印度的Kathiresan、叶龙武教授课题组和浙江大学陆展教授课题组在分子合成方面提供了重要帮助。瑞士伯尔尼大学Wandlowski教授和田中群教授为该工作提供了指导。【Abstract】The progress of plasmon-based technologies relies on an understanding of the properties of the enhanced electromagnetic fields generated by the coupling nanostrucutres.Plasmon-enhanced applications include advanced spectroscopies, optomechanics, optomagnetics and biosensing. However, precise determination of plasmon field intensity distribution within a nanogap remains challenging. Here, we demonstrate a molecular ruler made from a set of viologen-based, self-assembly monolayers with which we precisely measures field distribution within a plasmon nanocavity with ~2-Å spatial resolution. We observed an unusually large plasmon field intensity inhomogeneity that we attribute to the formation of a plasmonic comb in the nanocavity. As a consequence, we posit that the generally adopted continuous media approximation for molecular monolayers should be used carefully.The progress of plasmon-based technologies relies on an understanding of the properties of the enhanced electromagnetic fields generated by the coupling nanostrucutres1,2,3,4,5,6. Plasmon-enhanced applications include advanced spectroscopies7,8,9,10, optomechanics11, optomagnetics12 and biosensing13,14,15,16,17. However, precise determination of plasmon field intensity distribution within a nanogap remains challenging. Here, we demonstrate a molecular ruler made from a set of viologen-based, self-assembly monolayers with which we precisely measures field distribution within a plasmon nanocavity with ~2-Å spatial resolution. We observed an unusually large plasmon field intensity inhomogeneity that we attribute to the formation of a plasmonic comb in the nanocavity. As a consequence, we posit that the generally adopted continuous media approximation for molecular monolayers should be used carefully.The Swedish National Infrastructure for Computing is acknowledged for computer time. S.D. is sponsored by Shanghai Pujiang Programme (grant no. 19PJ1400600). 该研究工作得到国家自然科学基金、国家重点研发计划、安徽省量子信息技术引导专项等的资助和支持

Synthesis, Characterization and Host-Guest Complexation Studies of Dendritic and Linear Pyridinium Derivatives

Convergent and divergent strategies for the synthesis of viologen dendrimers with 1,3,5-tri-methylene branching units are presented. The synthesis of 3,5-bis(hydroxymethyl) benzyl bromide was optimized. The analysis of the crystal structure of 1-[3,5-bis(hydroxymethyl)benzyl]-4-(pyridin-4-yl) pyridinium hexafluorophosphate together with PM3 calculations opens an avenue to judge the structure and conformation of benzylic viologen dendrimers. In order to study chemical trigger induced conformational changes, viologen dendrimers were spin-labeled via a divergent approach. 1-(2,4-dinitrophenyl)-4-(pyridin-4-yl)pyridinium hexafluorophosphate was used as the end group to yield an activated dendrimer of the respective generation. The corresponding dendrimers were spin-labeled by reacting the active functionality with 4-amino TEMPO. The products were characterized by ESR (spin-label efficiency) and conventional cyclic voltammetry. Dynamic ESR studies are planned. New trimethylene-dipyridinium dendrimers were synthesized via a divergent approach using 4-tert-butylbenzyl group as the peripheral group. These dendrimers are well soluble in DMF or DMSO as PF6 salts and they act as a host for anthraquinone-2,6-disulfonate (AQDS). They can be stoichiometrically titrated with AQDS as shown by 1H-NMR, DOSY and cyclic voltammetry. Upon loading them with AQDS, the dendrimers undergo first a contraction, they reach a minimum hydrodynamic radius for complete charge compensation and they re-open when overcharging takes place. The contraction is supported by MM+ calculations. Upon stepwise loading of G2 (42 positive charges) with AQDS (2 negative charges), the first 3 molar equivalents (6 neg. charges) occupy the innermost dendrimer shell (consisting of 6 pos. charges), the next 6 equivalents (12 neg. charges) occupy the middle shell (12 pos. charges) and the last 12 equivalents AQDS (24 neg. charges) occupy the outermost shell of the dendrimer (24 pos. charges), as supported by 1H-NMR titrations yielding the magic equivalent numbers of 3, 9=3+6, and 21=3+6+12. Such stepwise radial complexations again in DMSO were further demonstrated using other molecular guests (mono-, di- and trianionic) as well as with on purpose synthesized viologen dendrimers. α,ω-dibromoalkanes were bifunctionalized in two steps to yield alkyl phosphonates with pyridinium, trimethylenedipyridinium, bipyridinium or a sulfonate at their ω end. These compounds were used as surface modifiers to build biomimetic membranes on the pore walls of mesoporous TiO2. Host-guest interaction studies with on purpose synthesized viologen compounds have been performed in collaboration

Evaluation of the complexation behaviour among functionalized diphenyl viologens and cucurbit[7] and [8]urils

Abstract The complexation behaviour of Diphenyl viologens (DPVs) with Cucurbit[n]urils (CB[n]) was evaluated in detail and the results were reported. In this work, we present the synthesis of various DPVs functionalised with electron withdrawing and electron donating groups (EWGs & EDGs) and investigate their complexation behaviour with CB[7] and CB [8]. Carboxylic acid functionalized DPV’s (DPV-COOH) complexation with CB[8] gives additional insights, i.e., indicates hydrogen bonding plays an effective role in the complexation. The formation of a 2:2 quaternary complex of DPV-COOH/CB[8] under neutral pH conditions was supported by various analytical techniques. The complexation of DPVs with CB[7] specifies that irrespective of the functional group attached, they all form a 1:2 ternary complex, but the findings elaborate that the pattern followed in the complexation depends on the EW or EDG attached to the DPVs. The competition experiments conducted between functionalized DPVs and CB[7], CB[8] shows that they have more affinity towards CB[8] than CB[7] because of the better macrocyclic confinement effect of CB[8], as confirmed using UV–Vis spectroscopy. The binding affinity among EWG and EDG functionalised DPVs with CB[8] concludes EDG functionalised DPVs show better affinity towards CB[8], because they can form a charge transfer complex inside the CB[8] cavity. Exploring these host–guest interactions in more complex biological or environmental settings and studying their impact on the functionality of DPVs could be an exciting avenue for future research

Facile Construction of a Supramolecular Organic Framework Using Naphthyl Viologen Guests and CB[8] Host via Charge-Transfer Complexation

Herein, we report the synthesis of guest–host systems comprising naphthyl–viologen–naphthyl (Np–Vio–Np) and viologen–naphthyl–viologen (Vio–Np–Vio) guest molecules and their subsequent supramolecular polymerization in the presence of a CB[8] host in water. In addition, the guest complexation of ethyl-terminated trimeric viologen (ETV) with Np–Vio–Np and CB[8] was investigated. As a result of supramolecular interactions, 2D supramolecular organic frameworks with high internal periodicity were constructed. 1H NMR studies clearly demonstrated the formation of a host-stabilized charge-transfer complex via folding back (Np–Vio–Np and Vio–Np–Vio) in the presence of CB[8]. In the case of ETV + Np–Vio–Np + CB[8], a large polymeric network was formed as indicated by the NMR titrations. UV–vis and fluorescence studies clearly confirm the formation of an inter/intra molecular CT complex upon complexation with cucurbit[8]­uril. The size obtained using the dynamic light scattering (DLS) method pinpoints the formation of larger supramolecular aggregates in the order of μm through host–guest assembly, which is further complemented by FESEM and TEM. SAXS measurements indicate the formation of a 2D supramolecular polymer/polymer aggregate with long-range order

Solid-State Photodimerization Reaction with Photosalient Effect and Photophysical and Electrochemical Properties of <i>N</i>‑Methylated 1‑Naphthylvinyl-4-Quinoline

Crystal packing-dependent photochemical reactions of several functional olefins have been explored, but not for 1-naphthylvinyl-4-quinoline (NVQ) and analogous N-methylated 1-naphthylvinyl-4-quinoline cation (MNVQ). Herein, crystal structure elucidation and photophysical and electrochemical properties for both NVQ and MNVQ, and photodimerization reaction with a photosalient effect for MNVQ have been investigated for the first time. The neutral compound NVQ stacks parallel in its crystal; however, having a distance of 4.43 Å between the CC bonds, it remained photoinert. Upon methylation at the quinoline-N, the resulting MNVQ cations stack parallel in a head-to-tail fashion with a distance of 3.6 Å between the CC bonds, and consequently it underwent [2 + 2] photocycloaddition reaction quantitatively to MQNCB dication, when irradiated under visible light (∼410 nm). Monitoring closely the single crystals of MNVQ under blue light showed that they burst upon exposure for 1 min, signifying a photosalient behavior. Measurements of photophysical properties showed that MNVQ exhibited a bathochromic shift in both absorption (by 4772 cm–1) and emission (by 6198 cm–1) compared to the neutral NVQ. Upon photodimerization, the MQNCB dication exhibited a hypsochromic and hypochromic shift both in absorption and emission compared to the MNVQ cation, a signature of cessation of conjugation. Cyclic voltammetry (CV) measurements showed that all three compounds are redox active and exhibit a reversible reduction event in the range of −0.6 to −0.9 V (vs Ag/AgCl). Experimental results have been substantiated by theoretical calculations