Dipolar Self-Consistent Field Theory for Ionic Liquids: Effects of Dielectric Inhomogeneity in Ionic Liquids between Charged Plates

We studied ionic liquids confined between charged plates to develop a dipolar self-consistent field theory (DSCFT) for incompressible states and a hybrid of DSCFT combined with Monte Carlo simulation for compressible states. Our theory, which has no adjustable parameters, accounts for the differences between the dipole moments and the molecular volumes of the cation and anion, the hard-core nature of the ions, and the electrical double layer formed through the strong association of the ions with the electrodes. We illustrate that a spatial change in the distributions of cations and anions with different dipole moments causes a significant spatial change in the dielectric function and hence gives rise to spatial asymmetry in the electrostatic field between the charged plates. Notably, this effect can be comparable to that caused by an asymmetry in the molecular volumes of the cation and anion. Moreover, the hard-core nature of ionic liquids causes oscillations in the density profile near the charged plates. We also demonstrate that a contrast in the dielectric values of the cations and anions in ionic liquids causes a substantial decrease in capacitance as the applied voltage is increased. The magnitude of this variation can be noticeably altered by changing the dipole moments of the cation and anion

Hierarchical manipulation of uniform multi-nanoparticles by electrochemical coupling assembly

Assembling multiple nanomaterials into a single nanostructure is a promising way to obtain a multifunctionality derived from each building block. We address here the need for a general all-solution processed strategy to control the fabrication of multiple nanoparticles (NPs) at room temperature and under vacuum free conditions. The monodisperse multiple NPs were integrated successively into thin bulk-hybrid gradient or periodic tandem multilayer films through tuning the cycling number of cyclic voltammetry (CV), which are based on the quantitatively electrochemical deposition of each type of NPs thanks to the electrochemical coupling reaction of the N-alkylcarbazole ligand. This simple method yields nanoporous, transparent, stable and photoactive films with a hierarchical structure of multiple uniform NPs, exemplified by the prototype photodetector devices. Significantly, this strategy opens an avenue to fabricate low-cost wire and 3-dimensional NPs films on physically flexible conducting substrates

Synthesis and Multi-Stimuli-Responsive Behavior of Poly(N,N-dimethylaminoethyl methacrylate) Spherical Brushes under Different Modes of Confinement in Solution

We report the synthesis and solution behavior of photo-, temperature-, pH-, and ion-responsive weak polyelectrolyte spherical brushes under different modes of confinement. The spherical brushes were prepared by copolymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) and 7-(2-methacryloyloxyethoxy)-4-methylcoumarin anchored to silica nanoparticles via surface-initiated atom transfer radical polymerization. The photo-cross-linking and reversibility of the nanoparticle-attached coumarin entities are detected by UV-visible spectroscopy and dynamic light scattering (DLS). The cross-linking density of poly(DMAEMA) (i.e., PDMAEMA) brushes could be easily controlled by alternating irradiation at wavelengths of 365 and 254 nm. Moreover, solution behavior under different pH levels and ionic strengths is systematically investigated in the PDMAEMA brush polyelectrolyte chains confined only by a hard core, the cross-linked PDMAEMA brush polyelectrolyte chains confined by a hard core and cross-linking points, and the corresponding hollow nanocapsules after removal of silica by etching-polyelectrolyte chains confined only by cross-linking points. These three models represent the different modes of confinement. DLS results indicate that the volume phase transition temperatures of the three models shift to lower temperatures with the increase in pH. The highest temperature is afforded to phase transition for hollow nanocapsules in solution, followed by the cross-linked PDMAEMA brushes. The hydrodynamic radius of the polyelectrolyte brush systems obviously decreases with the increase in ionic strength of the solution when adjusted by NaCl

Host-sensitized luminescence in LaNbO4:Ln(3+) (Ln(3+) = Eu3+/Tb3+/Dy3+) with different emission colors

In this work, a series of Eu3+, Tb3+, and Dy3+ singly-doped and co-doped LaNbO4 (LNO) phosphors have been synthesized by a high-temperature solid-state reaction route. X-ray diffraction (XRD) along with Rietveld refinement, diffuse reflection spectra, photoluminescence (PL) and cathodoluminescence (CL) properties, decay lifetimes, and PL quantum yields (QYs) were exploited to characterize the phosphors. Under UV excitation, energy transfer process from the host to the activators exists in the singlydoped samples, which leads to tunable emission color from blue to red for LNO: Eu3+, green for LNO: Tb3+, and yellow including white for LNO: Dy3+. In Eu3+ and Tb3+ co-doped phosphors, LNO: Eu3+, Tb3+, the energy transfers from the host to the activators and Tb3+ to Eu3+ ions have also been deduced from the PL spectra, resulting in tunable emission color from green to red by adjusting the concentration ratio of Eu3+ and Tb3+ ions. The decay times monitored at host emission and Tb3+ emission confirm the existence of energy transfer in the as-prepared samples. The best quantum efficiency can reach 43.2% for LNO: 0.01Tb(3+) among all the as-prepared phosphors. In addition, the CL spectra of LNO: Eu3+/Tb3+/Dy3+ are a little different from their PL spectra because another emission envelope around 530 nm appears in the samples, which is attributed to the bombardment of higher energy excitation source of low-voltage electron beam. However, the characteristic emissions similar to PL spectra were reserved. Moreover, the CL spectrum of LNO: 0.02Tb(3+) has stronger emission intensity than that of ZnO:Zn commercial product. These results from the PL and CL properties of LNO: Eu3+/Tb3+/Dy3+ suggest their potential in solid-state lighting and display fields

Templated Self-Assembly of Block Copolymers and Morphology Transformation Driven by the Rayleigh Instability

In the current study, we investigate the self-assembly of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) confined in the nanopores of the anodic aluminum oxide (AAO) template and the subsequent morphology transformation induced by the Rayleigh instability. PS-b-P4VP nanotubes and nanorods with various internal nanostructures are fabricated by wetting the AAO template with PS-b-P4VP/chloroform solution, and then followed by solvent evaporation. After the removal of AAO template by potassium hydroxide solution, several different solvents (chloroform, toluene, and N,N-dimethylformamide) with different qualities are used to swell and anneal those nanotubes and nanorods suspended in aqueous media. Morphology transformation from nanostructured PS-b-P4VP nanotubes or nanorods to ordered nanospheres is observed by annealing upon chloroform and toluene while the morphology remains unchanged upon N,N-dimethylformamide annealing, indicating that solvent quality is a key factor in tuning the morphology and internal structures. Kinetics study and theoretical analysis for the morphology transition from two-dimensional (2D) block copolymer (BCP) nanotubes and nanorods to three-dimensional (3D) BCP nanospheres are further performed. From the morphological evolution and the quantitative calculation, it is confirmed that this transition is induced by the Rayleigh instability. This study provides a simple but promising method, that is, solvent annealing method, for the fabrication of BCP nanospheres with ordered internal nanostructures, which may have great application in drug delivery and other nanotechnology

Magnetic-field-enabled resolution enhancement in super-resolution imaging

A novel strategy for modulating the photophysics of organic dyes in super-resolution fluorescence imaging using an external magnetic field was reported. The magnetic field induced increase in fluorescence intensity, localization number of probe molecules, and the number of photons emitted per molecule as compared to those acquired without a magnetic field were experimentally confirmed. Improved dSTORM localization precision and imaging resolution were consequently achieved

One-step synthesis of trimetallic Pt-Pd-Ru nanodendrites as highly active electrocatalysts

Precise control over composition and structure is highly important for designing highly active nanostructured electrocatalysts. Herein, we report a one-step strategy to directly synthesize trimetallic Pt-Pd-Ru nanodendrites in an aqueous solution at room temperature. These newly designed nanodendrites exhibit superior catalytic activities for both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in comparison with bimetallic Pt-Pd nanoflowers and commercially available Pt/C catalysts

A straightforward synthesis of alkyl 1H-tetrazol-5-yl thioethers via a one-pot reaction of aldehydes and 1H-tetrazole-5-thiols mediated by N-tosylhydrazones

A straightforward approach for the synthesis of alkyl 1H-tetrazol-5-yl thioethers from aldehydes and 1H-tetrazole-5-thiol through a one-pot procedure is presented. The aldehydes were first condensed with N-tosylhydrazine to generate the N-tosylhydrazones, which were then reductively coupled in situ with 1H-tetrazole-5-thiols under metal-free conditions to afford the thioethers in high to excellent yields

Microfluidic-based controllable synthesis of Pt nanocatalysts supported on carbon for fuel cells

A simple custom-made microfluidic reactor is used to synthesize Pt nanoparticles supported on carbon (Pt/C) as electrocatalysts for fuel cells. By varying the flow rate of reactant in the microfluidic reactor, Pt/C catalyst obtained with a flow rate of 90 mu L min(-1) of substrate was found to be optimal for both anode and cathode electro-catalytic reactions (oxygen reduction reaction (ORR), methanol and formic acid electro-oxidation). An optimal size of Pt nanoparticles was found to be about 2.8 nm. This microfluidic reactor provides a versatile and portable approach to the large-scale synthesis of uniformlydispersed carbon supported precious metal catalysts with high performance for fuel cells. The preparation is portable, versatile, fast and energy efficient, and can be a general method for the preparation of other supported metal and alloy systems

吡啶亚胺(胺)钒烯烃聚合催化剂(英文)

设计合成了一系列以吡啶二亚胺、吡啶胺-亚胺和吡啶二胺为螯合配体的三价钒配合物2a~2e,并通过红外和元素分析等技术手段对其进行了结构表征。在助催化剂和再生活化剂的存在下,这些催化剂展示出了高活性和良好的高温稳定性。得到高相对分子质量、单峰分布聚乙烯表明聚合体系为单活性中心。以吡啶二胺为螯合配体的配合物2e(2,6-bis[2,6-(iPr)2PhN C(Me)]2(C5H3N)VCl)在50℃下显示出的活性高达6.96 kg PE/mmolV·h,且在70℃时仍保持高的催化活性,这表明双阴离子吡啶二胺能更好的保护催化活性中心。此外,这类三价钒催化剂能高活性催化乙烯-降冰片烯及乙烯-己烯共聚,在温和条件下即可得到较高单体插入率(降冰片烯37.3%,己烯4.8%)的共聚物