Fabrication of single crystal CuGaS2 nanorods by X-ray irradiation

CuGaS(2) nanorods were synthesized by irradiating the precursor solution with intense X-rays. The products are single crystal nanorods with preferential [220] growth and a uniform size distribution. We also report on the photoresponse of drop-cast films of these nanorods.     

Spectral investigation of the intramolecular charge-transfer in some aminotriazole Schiff bases

3-Amino-1,2,4-triazole Schiff bases were reported to contain intramolecular charge-transfer. The enhancing and depressing effects were remarkable as the substituent was changed from electron-donating to electron-withdrawing groups. The path of the resonating delocalization was reversed in the case of the p-NO2 group. To validate these results we effectively used Weinhold et al's natural bond orbital analysis to assess the UV and FT-IR spectrophotometric monitoring of the change reflected in this phenomenon when the substituent in the benzene ring is altered. The NBO analysis was simulated by ab inito computations at the HF/6-31G(d) level of theory, in order to properly detect any possible presence of a hydrogen bond association. The changes occurring in electron occupancies of double-centered bonds, antibonding orbitals and in lone-pair orbitals appraised the results, as did the s and p character listings of the two-centered bonds and the simultaneous changes occurring in the geometric parameters of the molecules in question. Contrary to its normal preference, in these molecules the nitrogen used sp2 hybrid orbitals for its interaction, housing its electron lone-pair in the third p hybrid orbital. Furthermore, NBO analysis reflected the presence of a very soft intramolecular hydrogen association (C-H?π), labelled by UV and FT-IR assignments, between the benzene and triazole rings in all Schiff bases but p-N(Me)2. The n-π* stabilization energy decreased in the order: p-OH>p-OCH3>p-Cl>p-CH3>H>p-NO2>o-OH. The relation between the band position and Hammett substitution constant is interpreted in relation to the molecular structure.     

Synthesis of cis- and trans-3-aminocyclohexanols by reduction of β-enaminoketones

We describe a protocol developed for the preparation of β-enaminoketones derived from 1,3-cyclohexanediones, and their subsequent reduction by sodium in THF-isopropyl alcohol to afford cis- and trans-3-aminocyclohexanols.     

Theoretical characterization of laser- and sympathetically-cooled ions in surface-electrode ion traps

Using molecular dynamics simulations we characterize theoretically Coulomb clusters of laser- and sympathetically-cooled ions in a five-wire surface-electrode ion trap. We show that the asymmetry of the trapping potential leads to significantly different cluster structures and ion energy distributions in comparison to conventionally used linear Paul traps and to an asymmetric segregation of the ions in bi-component Coulomb clusters. We explore the impact of our results on the implementation of sympathetic cooling of molecular ions in surface-electrode traps and discuss possible challenges for the realization of such experiments.     

Microfluidic immunomagnetic multi-target sorting--a model for controlling deflection of paramagnetic beads

We describe a microfluidic system that uses a magnetic field to sort paramagnetic beads by deflecting them in the direction normal to the flow. In the experiments we systematically study the dependence of the beads' deflection on bead size and susceptibility, magnet strength, fluid speed and viscosity, and device geometry. We also develop a design parameter that can aid in the design of microfluidic devices for immunomagnetic multi-target sorting.     

Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Investigation

Knowledge of the relative stabilities of alane (AlH(3)) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for 38 alane complexes with NH(3-n)R(n) (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH(2-n)R(n) (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amine-alane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine and obtaining upper limits of ΔG° for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the alane complex. On the basis of this, we conclude that only a subset of the tertiary amine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an alane-based hydrogen storage system.     

用蓝色光二极管测量掺钛蓝宝石飞秒激光脉冲宽度

用蓝色光二极管双光子跃迁光电流信号测量掺钛蓝玉石飞秒激光脉冲宽度，实验高精度地记录了二阶干涉自相关曲线及其精细结构，由于用蓝色二极管双光子跃迁代替了常用的二次谐波，而且光信号直接转化为电信号，从而使飞秒激光脉冲宽度的测量大为简化。     

Origin of the sphere-to-rod transition in cationic micelles with aromatic counterions: specific ion hydration in the interfacial region matters

Sphere-to-rod transitions of cetyltrimethylammonium (CTA+) micelles with dichlorobenzoate counterions are remarkably substituent dependent. Simultaneous estimates of the interfacial molarities of H2O, MeOH, and Cl- and 2,6- and 3,5-dichlorobenzoate (2,6OBz and 3,5OBz) counterions were obtained by the chemical trapping method in mixed micelles of CTACl/CTA3,5OBz and CTACl/CTA2,6OBz without added salt. Increasing the CTA3,5OBz mole fraction produces a marked concurrent increase in interfacial 3,5OBz- and a decrease in interfacial H2O concentrations through the sphere-to-rod transition. No abrupt concentration changes are observed with increasing CTA2,6OBz mole fraction. Counterion-specific changes in the interfacial water concentration may be a major contributor to the delicate balance of forces governing micellar morphology.     

How many Langmuirs are required for monolayer formation?

In the present work, we provide the exact answer to the title question employing a probabilistic approach. The average number of Langmuirs L required for monolayer formation was found to be equal to (1/i), i.e., the armonic series up to the nth term, where n is the number of adsorption sites. This result is particularly useful when a reduced number of adsorption sites is considered, such as adsorption on small terraces of nanoscopic dimensions where the value of n could be in the range of a few thousands sites. In this case, the use of integrated equations derived from the mean-field approach would provide completely misleading results.     

Cationic bis-cyclometalated iridium(III) diimine complexes and their use in efficient blue, green, and red electroluminescent devices

A series of cationic Ir(III) complexes with the general formula (C/N)2Ir(N/N)(+)PF6- featuring bis-cyclometalated 1-phenylpyrazolyl-N,C2' (C/N) and neutral diimine (N/N, e.g., 2,2'-bipyridyl) ligands were synthesized and their electrochemical, photophysical, and electroluminescent properties studied. Density functional theory calculations indicate that the highest occupied molecular orbital of the compounds is comprised of a mixture of Ir d and phenylpyrazolyl-based orbitals, while the lowest unoccupied molecular orbital has predominantly diimine character. The oxidation and reduction potentials of the complexes can be independently varied by systematic modification of either the C/N or N/N ligands with donor or acceptor substituents. The electrochemical redox gaps (E(ox)-E(red)) were adjusted to span a range between 2.39 and 3.08 V. All of the compounds have intense absorption bands in the UV region assigned to 1(pi-pi*) transitions and weaker charge-transfer (CT) transitions that extend to the visible region. The complexes display intense luminescence both in fluid solution and as neat solids at 298 K that is assigned to emission from a triplet metal-ligand-to-ligand CT (3MLLCT) excited state. The energy of the 3MLLCT state varies in nearly direct proportion to the size of the electrochemical redox gap, which leads to emission colors that vary from red to blue. Three of the (C/N)2Ir(N/N)(+)PF6- complexes were used as active materials in single-layer light-emitting electrochemical cells (LECs). Single-layer electroluminescent devices were fabricated by spin-coating the Ir complexes onto an ITO-PEDOT/PSS substrate followed by deposition of aluminum contacts onto the organic film. Devices were prepared that give blue, green, and red electroluminescence spectra (lambda(max) = 492, 542, and 635 nm, respectively), which are nearly identical with the photoluminescence spectra of thin films of the same materials. The single-layer LECs give peak external quantum efficiencies of 4.7, 6.9, and 7.4% for the blue, green, and red emissive devices, respectively.