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排序方式: 共有3211条查询结果,搜索用时 218 毫秒
61.
Raoul Plessius Vera Deij Prof. Dr. Joost N. H. Reek Prof. Dr. Ir. Jarl Ivar van der Vlugt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(58):13241-13248
Three Pt4L2L′2 heteroleptic rectangles ( 1 – 3 ), containing ditopic redox-active bis-pyridine functionalized perylene bisimide (PBI) ligands PBI-pyr2 ( L ) are reported. Co-ligand L′ is a dicarboxylate spacer of varying length, leading to modified overall size of the assemblies. 1H NMR spectroscopy reveals a trend in the splitting and upfield chemical shift of the PBI-hydrogens in the rectangles with respect to free PBI, most pronounced with the largest strut length ( 3 ) and least with the smallest strut length ( 1 ). This is attributed to increased rotational freedom of the PBI-pyr 2 ligand over its longitudinal axis (Npy-Npy), due to increased distance between the PBI-surfaces, which is corroborated by VT-NMR measurements and DFT calculations. The intramolecular motion entails desymmetrization of the two PBI-ligands, in line with cyclic voltammetry (CV) data. The first (overall two-electron) reduction event and re-oxidation for 1 display a subtle peak-to-peak splitting of 60 mV, whilst increased splitting of this event is observed for 2 and 3 . The binding of pyrene in 1 is probed to establish proof of concept of host-guest chemistry enabled by the two PBI-motifs. Fitting the binding curve obtained by 1H NMR titration with a 1:1 complex formation model led to a binding constant of 964±55 m −1. Pyrene binding is shown to directly influence the redox-chemistry of 1 , resulting in a cathodic and anodic shift of approximately 46 mV on the first and second reduction event, respectively. 相似文献
62.
Three one-dimensional ladder-like coordination polymers consisting of Cd6 metalloring as the building unit, {[Cd4LCl4]·3H2O}n ( 1 ), {[Cd3L(ClO4)(H2O)]ClO4·3H2O}n ( 2 ), and {[Cd6(L)2(NO3)2(CH3OH)(H2O)](NO3)2·2CH3OH·5H2O}n ( 3 ), were solvothermally constructed from a carboxylic functionalized bisazamacrocyclic ligand 4,4′-bis((4,7-bis(2-carboxyethyl)-1,4,7-triazacyclonon-1-yl)methyl)-1,1′-biphenyl (H4L). These compounds dispersed in ethanol show the multiple emissions originating from the monomeric and intramolecularly overlapping biphenyl moieties which could be sensitively quenched by picric acid (PA) and 4-nitrophenol (4-NP) through the effective fluorescence resonance energy transfer process. The differential fluorescent responses of each compound on exposure to PA and 4-NP individually make the convenient ratiometric discrimination of two analytes based on the fluorescent intensity ratio (I320/I360) attainable, and 1 and 2 as ratiometric chemosensors for PA present a broad linear detection range from 4 to 300 μM with detection limits of 0.84 and 0.93 μM, respectively. Furthermore, the blue light emission of 1 under an ultraviolet lamp could be selectively quenched by PA even in the presence of all other interfering nitroaromatic pollutants, which empowers the fast visual detection of PA by naked eye. 相似文献
63.
以有序介孔碳(OMC)球为离子-电子转换层,制备了固态氯离子选择性电极,构建了基于离子敏感的场效应晶体管(ISFET)的手持式传感系统,用于检测人体血清中的氯离子。优化了OMC前驱体的碳化温度,探究了OMC形貌结构对电极传感性能的影响;电极柔性化制备后考察了其在手持系统中对氯离子的检测效果。结果表明,最优条件下,电极在5.12×10^-4~1.02 mol/L的浓度范围呈现线性响应,响应斜率为60 mV/decade。该柔性电极在手持传感系统中展现出高灵敏度和重现性,可用于人体血清样品中氯离子的检测,其回收率为96.3%~104.9%。 相似文献
64.
Joint L1/Lp-regularized minimization in video recovery of remote sensing based on compressed sensing
L1 regularization and Lp regularization are proposed for processing recovered images based on compressed sensing (CS). L1 regularization can be solved as a convex optimization problem but is less sparse than Lp (0 < p < 1). Lp regularization is sparser than L1 regularization but is more difficult to solve. This paper proposes joint L1/Lp (0 < p < 1) regularization, which combines Lp regularization and L1 regularization. This joint regularization is applied to recover video of remote sensing based on CS. Joint regularization is sparser than L1 regularization but is as easy to solve as L1 regularization. A linearized Bregman reweighted iteration algorithm is proposed to solve the joint L1/Lp regularization problem. The performance and capabilities of the linearized Bregman algorithm and linearized Bregman reweighted algorithm for solving the joint L1/Lp regularization model are analyzed and compared through numerical simulations. 相似文献
65.
Immobilization of AIEgens into metal‐organic frameworks: Ligand design,emission behavior,and applications
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Bo Gui Na Yu Yi Meng Fang Hu Cheng Wang 《Journal of polymer science. Part A, Polymer chemistry》2017,55(11):1809-1817
Aggregation‐induced emission (AIE), in which the luminophores are highly emissive in aggregate state, is one of the most unique photophysical phenomena and has shown interesting applications in many areas. The immobilization of AIE luminogens (AIEgens) into metal‐organic frameworks (MOFs), which are inorganic‐organic hybrid porous materials with tunable and predictable structures, has been investigated over the past few years. These well‐defined porous frameworks cannot only provide an ideal platform for studying the mechanism of AIE phenomenon in solid state, but also show potential applications from sensing to white light‐emitting diodes. In this highlight, we will summarize the recent progress of AIEgens‐based MOFs, including ligand design, emission behavior, and applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1809–1817 相似文献
66.
Chien Hsu Chih-Yuan Lin Amer Alizadeh Hirofumi Daiguji Wei-Lun Hsu 《Electrophoresis》2021,42(21-22):2206-2214
Resistive pulse sensing using solid-state nanopores provides a unique platform for detecting the structure and concentration of molecules of different types of analytes in an electrolyte solution. The capture of an entity into a nanopore is subject not only to the electrostatic force but also the effect of electroosmotic flow originating from the charged nanopore surface. In this study, we theoretically analyze spherical particle electrophoretic behavior near the entrance of a charged nanopore. By investigating the effects of pore size, particle–pore distance, and salt concentration on particle velocity, we summarize dominant mechanisms governing particle behavior for a range of conditions. In the literature, the Helmholtz–Smoluchowski equation is often adopted to evaluate particle translocation by considering the zeta potential difference between the particle and nanopore surfaces. We point out that, due to the difference of the electric field inside and outside the nanopore and the influence from the existence of the particle itself, the zeta potential of the particle, however, needs to be at least 30% higher than that of the nanopore to allow the particle to enter into the nanopore when its velocity is close to zero. Accordingly, we summarize the effective salt concentrations that enable successful particle capture and detection for different pore sizes, offering direct guidance for nanopore applications. 相似文献
67.
68.
Milan Jakubek Zdeněk Kejík Robert Kaplánek Hana Veselá David Sýkora Pavel Martásek 《Supramolecular chemistry》2018,30(3):218-226
Perimidine-based chelators 1 and 2 were prepared, and their structures were confirmed by 1H and 13C NMR, MS spectroscopy and elemental analysis. These compounds were studied as specific synthetic receptors for the recognition of transition metal ions. They exhibited high affinity and selectivity towards Cu(II) ions. The conditional binding constants, linear dynamic range and detection limit were determined by UV–vis spectroscopy. These parameters demonstrated high potential of the prepared synthetic receptors for the recognition and determination of Cu(II) ions. The minimum detectable concentrations of Cu(II) ions for the synthetic receptors 1 and 2 were 270 and 75 nM (R 2 = 0.9915 and 0.9964) in aqueous medium (water/DMSO; 99:1 (v/v)), respectively. 相似文献
69.
70.
A new expression is proposed to determine the unperturbed dimensions of coil-like polymers viscometrically by use of the Flory and Kratky expression. The unperturbed dimensions so estimated are compared with the results obtained by using different expressions available in the literature. The results are comparable even for stiff chain polymers. The data obtained under theta conditions also fit this expression very well. The effect of molecular weight, its distribution, and that of the solvent has also been studied. It is concluded that the unperturbed dimensions are independent of molecular weight and solvent but depend on the heterogeneity of the system. 相似文献