A semi-empirical approach to the modeling of the electrophoretic mobility in free solution: application to polystyrenesulfonates of various sulfonation rates

This work focuses on the understanding of the electrophoretic behavior of flexible chains of polystyrenesulfonates (PSSs) in free solution. It deals mainly with the variation of the electrophoretic mobility with (i) the polymerization degree (N) of fully sulfonated PSSs and (ii) the sulfonation rate of randomly sulfonated PSSs. In both cases, the electrophoretic mobility was modeled following a semi-empirical approach which involves parameters retaining a physical meaning. Fully sulfonated PSS oligomers, having a length smaller than or similar to the Debye length, exhibit a particular electrophoretic behavior, in-between that observed for multicharged small molecules and that for polyelectrolytes. The electrophoretic mobility of these oligomers increases strongly with N, which is attributed to a hydrodynamic coupling between monomers. Then the mobility is maximum for an N of about 10, for which the PSS oligomers are still in a rod-like conformation. Afterwards, as N increases and the PSSs are larger than the Debye length, the electrophoretic mobility decreases slowly until it reaches a constant value corresponding to the free-draining behavior. Next, the electrophoretic behavior of long PSS (N about 1,200) differing in their sulfonation rates was investigated. The effective charge rates were determined independently by conductimetric measurements and the mobilities were modeled as a function of the sulfonation rate. The PSS behavior observed was compared to the one previously reported for classical polyelectrolytes having hydrophilic backbones, such as copolymers of poly(acryamide-coacrylic acid). A specific behavior has been pointed out for these partially sulfonated PSSs, which is attributed to the hydrophobicity of their backbone. Finally, it is shown that separations of PSSs of different sulfonation rates can be obtained with electrolytes containing an anionic surfactant or methanol.     

Measurements of extinction by aerosol particles in the near-infrared using continuous wave cavity ring-down spectroscopy

Cavity ring-down spectroscopy using a fiber-coupled continuous wave distributed feedback laser at a wavelength of 1520 nm has been used to measure extinction of light by samples of nearly monodisperse aerosol particles <1 μm in diameter. A model is tested for the analysis of the sample extinction that is based on the Poisson statistics of the number of particles within the intracavity laser beam: variances of measured extinction are used to derive values of the scattering cross section for size-selected aerosol particles, without need for knowledge of the particle number density or sample length. Experimental parameters that influence the performance of the CRD system and the application and limitations of the statistical model are examined in detail. Determinations are reported of the scattering cross sections for polystyrene spheres (PSSs), sodium chloride, and ammonium sulfate, and, for particles greater than 500 nm in diameter, are shown to be in agreement with the corresponding values calculated using Mie theory or Discrete Dipole Approximation methods. For smaller particles, the experimentally derived values of the scattering cross section are larger than the theoretical predictions, and transmission of a small fraction of larger particles into the cavity is argued to be responsible for this discrepancy. The effects of cubic structure on the determination of optical extinction efficiencies of sodium chloride aerosol particles are examined. Values are reported for the real components of the refractive indices at 1520 nm of PSS, sodium chloride, and ammonium sulfate aerosol particles.     

大粒径单分散金纳米粒子的水相合成

近年来,随着纳米科技的兴起,纳米尺度的金颗粒以其独特的光学、电学性质［１-３］在许多领域表现出潜在的应用价值,引起了人们浓厚的研究兴趣［４-７］．迄今为止,已有多种制备金纳米粒子的方法见诸报导．制备简便、单分散性好、粒径可控,一直是各种方法追求的目标．...     

Scientific Importance of Water‐Processable PEDOT–PSS and Preparation,Challenge and New Application in Sensors of Its Film Electrode: A Review

In this review, PEDOT–PSS is mainly a commercially available PEDOT–PSS, which is a water‐dispersible form of the intrinsically conducting PEDOT doped with the water‐soluble PSS, including its derivatives, copolymers, analogs (PEDOT:PSSs), even their composites via the chemical or physical modification toward the structure of PEDOT and/or PSS. First, we will focus on discussing the scientific importance of PEDOT–PSS in conjunction with its extraordinary properties and broad multidisciplinary applications in organic/polymeric electronics and optoelectronics from the viewpoint of the historical development and the promising application of representative ECPs. Subsequently, versatile film‐forming techniques for the preparation of PEDOT–PSS film electrode were described in details, including common coating approaches and printing techniques, and many emerging preparative methods were mentioned. Then challenges (e.g., conductivity, stability in Water, adhesion to substrate electrode) of PEDOT–PSS film electrode for devices under the high humidity/watery circumstances, especially electrochemical devices are discussed. Fourth, we take PEDOT–PSS film electrode for a relatively new application in sensors as an example, mainly summarized advances in the development of various sensors based on PEDOT–PSSs and their composites in combination with its preparative methods and extraordinary properties. Finally, we give the outlook of PEDOT–PSS for possible applications with the emphasis on PEDOT–PSS film electrode for electrochemical devices, including sensors. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1121–1150     

Low-temperature synthetic method for size-controlled CdSe nanocrystals: utilization of boron selenide

By employing B(2)Se(3) as a selenium source, we demonstrate that at reaction temperatures as low as 60 [degree]C, relatively monodisperse, fluorescent CdSe nanocrystals can be conveniently prepared in various sizes selected from 2 to 13 nm.     

A one-step aqueous synthetic route to extremely small CdSe nanoparticles

By employing Na2Se as a selenium source, we demonstrate that extremely small ( approximately 1 nm) mercapto acid-stabilized CdSe nanoparticles can be conveniently prepared in water. The as-prepared nanoparticles start to show dominant near band-gap photoluminescence in the blue spectral range and show high photoluminescence in the green spectral range.     

PHOTOREARRANGEMENT OF AZOXYBENZENE TO 2-HYDROXYAZOBENZENE: A CONVENIENT CHEMICAL ACTINOMETER*

Abstract— In ethanolic solution, the intramolecular photorearrangement of azoxybenzene occurs with quantum yield close to 0.02 over the range 250–350 nm. The reaction, which is independent of temperature and of concentration of reactant, is conveniently monitored by measuring the absorbance of the product, 2-hydroxyazobenzene, as its anion in alkaline solution.     

Synthesis and near-infrared characteristics of novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores

Novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores have been prepared conveniently by coupling of 1,8-naphthalimide and dibromoperylene bisimides. Their optical properties were investigated by UV-vis and fluorescence spectroscopy. The absorption spectra of these compounds showed wide spectral responses from 300 to 700 nm,which would be potentials for application as organic solar cells.     

Asymmetric dimers can be formed by dewetting half-shells of gold deposited on the surfaces of spherical oxide colloids

Asymmetric dimers consisting of gold microcrystals and spherical silica colloids have been fabricated by depositing thin films of gold onto the spherical colloids to form half-shells, followed by annealing at elevated temperatures. The capability and feasibility of this procedure have been demonstrated with silica and titania beads of 0.2-2 mum in diameter and gamma-Fe2O3/polystyrene@SiO2 core-shell particles 0.5 mum in size. The dimensions of gold microcrystals could be conveniently varied in the range of 100-650 nm by controlling the thickness of gold films and/or the diameter of the spherical colloids. This method provides another route to asymmetric dimers made of colloidal particles that could be different in size, chemical composition, surface functionality, density or sign of surface charge, bulk property, or a combination of these properties.     

Tetraglyme-mediated synthesis of Pd nanoparticles for dehydrogenation of ammonia borane

Palladium nanoparticles (PdNPs) were conveniently prepared in tetraglyme (TG) solution using a variety of palladium precursors. At 140 °C, TG promoted Pd(3)(OAc)(6) to produce irregular shaped PdNPs with an average size of 4 nm. When these PdNPs were re-dispersed in TG and used for the dehydrogenation of ammonia borane (AB) at 85 °C, remarkably enhanced catalytic performance was achieved to release 2.3 equiv. of H(2) in 1 h.     

Controlled synthesis of magnetic Pd/Fe3O4 spheres via an ethylenediamine-assisted route

A simple route based on time-dependent growth was employed to synthesize solid and hollow spheres of Pd/Fe(3)O(4) nanocomposite. Transmission electron microscopic (TEM) imaging shows that the spheres are composed of nanocrystals with the solid spheres having a diameter of 533 nm whereas the hollow ones having a diameter of 520 nm and a shell thickness of 100 nm. An assembly-then-growth mechanism for the formation of the magnetic Pd/Fe(3)O(4) nanocomposite has also been elucidated on the basis of the experimental observations. It is demonstrated that the Pd/Fe(3)O(4) nanocomposite functions as a heterogeneous catalyst for the hydrogenation reaction of p-nitrophenol at room temperature under atmospheric pressure. Both the solid and hollow spheres possess unique magnetic properties so that they may be conveniently separated and recovered by a magnet after the catalytic reaction.     

Radical reactions of C84

Pulse radiolysis and steady-state radiolysis experiments describing the radical and electron transfer reactions of C₈₄ are reported here for the first time. C₈₄ reacts readily with radiolytically generated chloromethyl (^•CCl₃) and trichloromethylperoxyl (CCl₃OO^•) radicals in CCl₄. The formation of the radical adduct has been confirmed from its characteristic absorption in the UV (320 nm) and visible (480 nm). Radical-induced oxidation in 1,2-dichloroethane (1,2-DCE) resulted in a short lived transient absorbing at 920 nm. Reduction of C₈₄ in toluene/2-propanol/acetone could be conveniently followed by formation of an absorption band with an absorption maximum at 960 nm.     

Synthesis of d-f coordination polymer nanoparticles and their application in phosphorescence and magnetic resonance imaging

Magneto-phosphorescent d-f coordination polymer nanoparticles (f-CPPs) were conveniently synthesized by phosphorescent carboxyl-functionalized iridium complexes as building blocks and magnetic Gd(III) ions as metallic nodes. They reveal uniform hollow spheres with an average diameter of around 60 nm and wall thickness of about 10 nm. Water soluble f-CPPs were obtained by polyvinylpyrolidone modification (denoted as f-CPPs@PVP), which had an intense red phosphorescence, moderate longitudinal relaxivity (r(1)) and low cytotoxicity. Furthermore, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and confocal laser scanning microscopy (CLSM) confirmed f-CPPs@PVP could be taken up by living cells effectively. Therefore, they should be a novel nano-bioprobe for the multimodal imaging of cancer cells.     

高质量CdSe量子点的水相制备与表征

以巯基丁二酸为稳定剂, 亚硒酸钠为硒源, 制备了高质量水溶性CdSe量子点. 研究了反应时间、 镉与硒的摩尔比及镉与巯基丁二酸的摩尔比等实验条件对CdSe量子点光谱性能的影响. 分别用紫外-可见光谱、 荧光光谱、 X射线粉末衍射和透射电子显微镜等对量子点进行表征. 结果表明, 采用这种方法制得的CdSe量子点为立方晶型, 量子点的荧光发射峰在518～562 nm范围内连续可调, 并且发射峰的半峰宽始终保持在35 nm左右, 荧光量子产率可达21%.     

Matrix-assisted laser desorption/ionization analysis of lipids and high molecular weight hydrocarbons with lithium 2,5-dihydroxybenzoate matrix

Lithium 2,5-dihydroxybenzoate (LiDHB) is shown to be a very effective matrix for matrix-assisted laser desorption/ionization (MALDI) analysis of nonpolar long-chain lipids, hydrocarbons and polymers. Under standard desorption and ionization conditions using a conventional nitrogen UV laser (337 nm), hydrocarbons (C(24)-C(40)), diverse lipids (triglycerides, diglycerides, wax esters from leaves) and saturated polymers are effectively lithiated providing [M+Li](+) ions. The formation of lithiated hydrocarbons is not accompanied by an elimination of hydrogen or other fragmentation reactions and, due to the relatively simple isotopic distribution of lithium, seems to be more useable for analysis of hydrocarbon mixtures than the previously used silver cationization agents. The mass calibration can be conveniently performed either externally or internally using poly(ethylene glycol) commercial standards.     

Nanoparticle‐Imprinted Polymers for Size‐Selective Recognition of Nanoparticles

Citrate‐stabilized gold nanoparticles 15 nm and 33 nm in diameter were transferred concomitantly with a monolayer of positively charged polyaniline by Langmuir–Blodgett transfer at pH 5 onto a conducting indium‐doped tin oxide (ITO) support. Films consisting of one to three layers of polyaniline with thicknesses of 1–3 nm were prepared and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy. After electro‐oxidation of the Au nanoparticles in 0.1 M KCl, cavities were left behind in the film that could be analyzed by SEM. These cavities were able to recapture analyte nanoparticles from a solution of pH 10 and showed size‐exclusion properties. The amount of nanoparticles taken up by the cavities was conveniently analyzed by measuring the charge associated with the electro‐oxidation of these particles in 0.1 M KCl after the film had been rinsed with water. The size‐exclusion properties improved with the number of Langmuir–Blodgett layers transferred.     

On the use of the activation energy concept to investigate analyte and network deformations in entangled polymer solution capillary electrophoresis of synthetic polyelectrolytes

The activation energy associated with the electrophoretic migration of an analyte under given electrolyte conditions can be accessed through the determination of the analyte electrophoretic mobility at various temperatures. In the case of the electrophoretic separation of polyelectrolytes in the presence of an entangled polymer network, activation energy can be regarded as the energy needed by the analyte to overcome the obstacles created by the separating network. Any deformation undergone by the analyte or the network is expected to induce a decrease in the activation energy. In this work, the electrophoretic mobilities of poly(styrenesulfonates) (PSSs) of various molecular weights (Mr 16 x 10(3) to 990 x 10(3)) were determined in entangled polyethylene oxide (PEO) solutions as a function of temperature (in the 17-60 degrees C range) and the PSS activation energies were calculated. The influences of the PSS molecular weight, blob sizes zetab of the separating network (related to the PEO concentration), ionic strength of the electrolyte and electric field strength (75-600 V/cm) were investigated. The results were interpreted in terms of analyte and network deformations and were confronted with those previously obtained for DNA migration in polymer solutions and chemical gels. For a radius of gyration Rgzetab, suggesting PSS and network deformations in the latter case. Increasing ionic strength resulted in an increase in the PSS activation energy, because of the decrease of their radii of gyration, which makes them less deformable. Finally, the activation energies of all the PSSs are a decreasing function of field strength and at high field strength tend to reach a constant value close to that for a small molecule.     

光度法快速分析苯乙酮酸含量的研究

研究了一种快速定量分析发酵液中苯乙酮酸的方法。在氢氧化钠溶液中,苯乙酮酸和2,4-二硝基苯肼形成一种红棕色的溶液,该溶液在458 nm处有最大吸收,据此可以快速分析混合物中苯乙酮酸的含量。该法在微生物还原苯乙酮酸生产D-扁桃酸的工艺中进行样品分析,结果表明方法简便、快速、灵敏度高,可以用于监控反应进程。     

Reduction of background interference in the spectrophotometric assay of mevalonate kinase

Mevalonate kinase can be conveniently assayed by coupling to two other reactions and monitoring the consumption of NADH optically at 340 nm. No mevalonate kinase was detected in crude extracts of Saccharomyces cerevisiae strains, however, because of background interference measured in the absence of mevalonate. A strain of S. cerevisiae over-expressing mevalonate kinase was used to establish conditions for reduction of background interference. This method has been successfully applied to S. cerevisiae strains containing a wild type level of mevalonate kinase.