Capture of CO2 by a Cationic Nickel(I) Complex in the Gas Phase and Characterization of the Bound,Activated CO2 Molecule by Cryogenic Ion Vibrational Predissociation Spectroscopy

We describe a systematic method for the preparation and spectroscopic characterization of a CO₂ molecule coordinated to an activated bisphenoidal nickel(I) compound containing a tetraazamacrocyclic ligand in the gas phase. The resulting complex was then structurally characterized by using mass‐selected vibrational predissociation spectroscopy. The results indicate that a highly distorted CO₂ molecule is bound to the metal center in an η²‐C,O coordination mode, thus establishing an efficient and rational method for the preparation of metal‐activated CO₂ for further studies using ion chemistry techniques.     

Effects of packing structure on the optoelectronic and charge transport properties in poly(9,9-di-n-octylfluorene-alt-benzothiadiazole)

Spin-coated poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) films of different molecular weights (Mn= 9-255 kg/mol), both in the pristine and annealed state, were studied in an effort to elucidate changes in the polymer packing structure and the effects this structure has on the optoelectronic and charge transport properties of these films. A model based on quantum chemical calculations, wide-angle X-ray scattering, atomic force microscopy, Raman spectroscopy, photoluminescence, and electron mobility measurements was developed to describe the restructuring of the polymer film as a function of polymer chain length and annealing. In pristine high molecular weight films, the polymer chains exhibit a significant torsion angle between the F8 and BT units, and the BT units in neighboring chains are close to one another. Annealing films to sufficiently high transition temperatures allows the polymers to adopt a lower energy configuration in which the BT units in one polymer chain are adjacent to F8 units in a neighboring chain ("alternating structure"), and the torsion angle between F8 and BT units is reduced. This restructuring, dictated by the strong dipole on the BT unit, subsequently affects the efficiencies of interchain electron transfer and exciton migration. Films exhibiting the alternating structure show significantly lower electron mobilities than those of the pristine high molecular weight films, due to a decrease in the efficiency of interchain electron transport in this structure. In addition, interchain exciton migration to low energy weakly emissive states is also reduced for these alternating structure films, as observed in their photoluminescence spectra and efficiencies.     

Photoelectron spectroscopy of sodium chloride anions with two excess electrons

Photoelectron spectroscopy measurements of (NaCl)_nNa^? (n=1–13, except n=10) are reported. The observed electron energy spectra fall into three distinct types, reflecting different correlations between the two excess electrons and ions. Depending on the host clusters' structures, the experimental evidence indicates that the two excess electrons in these sodium chloride clusters could be spin paired, forming a bipolaron or a Na^? anion. The two excess electrons could also be spin parallel, forming a double F-center state.     

Effects of mucin addition on the stability of oil–water emulsions

In this work, bovine submaxillary gland mucin (BSM) was used as an emulsifier to stabilize oil–water emulsion systems. Prior to use, commercial BSM was purified by jacalin affinity chromatography. Emulsions consisting of 5% mineral oil in phosphate buffered saline (PBS) were prepared through the addition of different amounts of purified mucin followed by sonication using either of two methods: (1) low energy input for a long time (2 h), or (2) high energy input for a short time (20 s). The surfactancy property of mucin was investigated by surface tension measurements, which showed the BSM to greatly reduce the surface tension of PBS. Compared to several synthetic surfactants of the Pluronic® type, mucin showed comparable or better surface activity than F68, F88 and F108 products in dilute solutions. The formed emulsions had a mean droplet size that decreased monotonically with increasing concentration of mucin until a plateau was reached at concentrations around 0.1% by weight. The stability of these emulsions was evaluated by monitoring their average droplet size during a 33-day period. Emulsions with more than 0.25% mucin showed a constant mean size throughout the period. Specifically, an emulsion produced with 0.95% mucin showed a stable mean droplet size of about 300 nm. The stability of the mucin-emulsified systems was also evaluated by measuring turbidity changes with time, which allowed a comparison with similar emulsions stabilized by the Pluronic® surfactants in the same concentration. Thus, mucin showed its ability to establish more stable and more efficient oil–water emulsion systems. Since mucin is a glycoprotein, and hence biodegradable, our results suggest that mucin might serve as an ideal biological surfactant for the stabilization of emulsion systems intended for biomedical and pharmaceutical applications.     

An Aggregation‐Induced‐Emission Platform for Direct Visualization of Interfacial Dynamic Self‐Assembly

An in‐depth understanding of dynamic interfacial self‐assembly processes is essential for a wide range of topics in theoretical physics, materials design, and biomedical research. However, direct monitoring of such processes is hampered by the poor imaging contrast of a thin interfacial layer. We report in situ imaging technology capable of selectively highlighting self‐assembly at the phase boundary in real time by employing the unique photophysical properties of aggregation‐induced emission. Its application to the study of breath‐figure formation, an immensely useful yet poorly understood phenomenon, provided a mechanistic model supported by direct visualization of all main steps and fully corroborated by simulation and theoretical analysis. This platform is expected to advance the understanding of the dynamic phase‐transition phenomena, offer insights into interfacial biological processes, and guide development of novel self‐assembly technologies.     

Experimental and theoretical studies of the structure of alkali halide clusters

We have investigated the structures and properties of alkali halide cluster ions produced by laser vaporization of solid samples. In many alkali halide cluster ions, we observe the appearances of bulk-like characteristics even at sub-nanometer sizes:fcc crystalline structures (including surface terraces), ionic binding, and a susceptibility to common bulk defects such as F and H color-centers. To understand the origins of cluster structures, we have made calculations of ground state energetics, high-temperature molecular dynamics, and the electronic structure of clusters having excess electrons.     

Silole‐containing poly(silylenevinylene)s: Synthesis,characterization, aggregation‐enhanced emission,and explosive detection

Hydrosilylation polymerizations of 1,1‐dimethyl‐2,5‐bis(4‐ethynylphenyl)‐3,4‐diphenylsilole with aromatic silylhydrides including 1,4‐bis(dimethylsilyl)benzene, 4,4′‐bis(dimethylsilyl)biphenyl, 2,5‐bis(dimethylsilyl)thiophene, and 2,7‐bis(dimethylsilyl)‐9,9‐dihexylfluorene in the presence of Rh(PPh₃)₃Cl catalyst in refluxed tetrahydrofuran afford a series of silole‐containing poly(silylenevinylene)s. Under optimum condition, the alkyne polyhydrosilylation reactions progress efficiently and regioselectively, yielding polymers with high molecular weights (M_w up to 95,300) and good stereoregularity (E content close to 99%) in high yields (up to 92%). The polymers are processable and thermally stable, with high decomposition temperatures in the range of 420?449 °C corresponding to 5% weight loss. They are weakly fluorescent in the solution state but become emissive in the aggregate and film states, demonstrating their aggregation‐enhanced emission characteristics. The explosive sensing capabilities of the polymers are examined in both solution and aggregate states. The emissions of the polymers aggregates in aqueous mixture are quenched more efficiently by picric acid in an exponential pattern with high quenching constants (up to 27,949 L mol^?1), suggesting that the polymers aggregates are sensitive chemosensors for explosive detection. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Tiopronin gold nanoparticle precursor forms aurophilic ring tetramer

In the two step synthesis of thiolate-monolayer protected clusters (MPCs), the first step of the reaction is a mild reduction of gold(III) by thiols that generates gold(I) thiolate complexes as intermediates. Using tiopronin (Tio) as the thiol reductant, the characterization of the intermediate Au(4)Tio(4) complex was accomplished with various analytical and structural techniques. Nuclear magnetic resonance (NMR), elemental analysis, thermogravimetric analysis (TGA), and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) were all consistent with a cyclic gold(I)-thiol tetramer structure, and final structural analysis was gathered through the use of powder diffraction and pair distribution functions (PDF). Crystallographic data has proved challenging for almost all previous gold(I)-thiolate complexes. Herein, a novel characterization technique when combined with standard analytical assessment to elucidate structure without crystallographic data proved invaluable to the study of these complexes. This in conjunction with other analytical techniques, in particular mass spectrometry, can elucidate a structure when crystallographic data is unavailable. In addition, luminescent properties provided evidence of aurophilicity within the molecule. The concept of aurophilicity has been introduced to describe a select group of gold-thiolate structures, which possess unique characteristics, mainly red photoluminescence and a distinct Au-Au intramolecular distance indicating a weak metal-metal bond as also evidenced by the structural model of the tetramer. Significant features of both the tetrameric and the aurophilic properties of the intermediate gold(I) tiopronin complex are retained after borohydride reduction to form the MPC, including gold(I) tiopronin partial rings as capping motifs, or "staples", and weak red photoluminescence that extends into the Near Infrared region.     

Small molecule chemisorption on indium-tin oxide surfaces: enhancing probe molecule electron-transfer rates and the performance of organic light-emitting diodes

Indium-tin oxide (ITO) surfaces have been modified by chemisorption of carboxylic acid functionalized small molecules: ferrocene dicarboxylic acid (1), 3-thiophene acetic acid (2), and 6-{4-[{4'-[[4-(5-carboxy-pentyloxy)-phenyl]-(4-methoxy-phenyl)-amino]-biphenyl-4-yl}-(4-methoxy-phenyl)-amino]-phenoxy}-hexanoic acid (p-OMe)2-TPD-(C5-COOH)2) (3). Voltammetrically determined surface coverages of 1-3 increased in two stages, the first stage completing in minutes, the latter stage taking several hours. Electron-transfer rate coefficients, kS, for the probe molecule ferrocene in acetonitrile likewise increased in two stages with increasing surface coverages of 1, 2, and 3. Fourier transform infrared spectroscopy of In2O3 powders, exposed for long periods to ethanol solutions of each modifier, confirmed the formation of indium oxalate-like surface species. X-ray photoelectron spectroscopy of carboxy-terminated alkanethiol-modified gold surfaces, exposed to these same In2O3(powder)/small molecule modifier solutions, showed the capture of trace levels of indium as a result of the chemisorption of these small molecules, suggesting that slow etching of the ITO surface also occurs during the chemisorption event. Conventional aluminum quinolate/bis-triarylamine organic light-emitting diodes (OLEDs) created on ITO surfaces modified with 1, 2, and 3, with and without an overlayer of PEDOT:PSS (a poly(thiophene)/poly(stryenesulfonate) ITO modifier), showed leakage currents lowered by several orders of magnitude and an increase in OLED device efficiency.