Ternary compound CuInTe2: a promising thermoelectric material with diamond-like structure

We report a ternary compound CuInTe(2) with diamond-like structure as a promising thermoelectric material in moderate temperature range. Due to the good electrical properties and low thermal conductivity, the zT value of CuInTe(2) reaches 1.18 at 850 K, better than any other un-doped diamond-like material.     

Time dependent diffusion in a disordered medium with partially absorbing walls: a perturbative approach

We present an analytical study of the time dependent diffusion coefficient in a dilute suspension of spheres with partially absorbing boundary condition. Following Kirkpatrick [J. Chem. Phys. 76, 4255 (1982)] we obtain a perturbative expansion for the time dependent particle density using volume fraction f of spheres as an expansion parameter. The exact single particle t operator for partially absorbing boundary condition is used to obtain a closed form time dependent diffusion coefficient D(t) accurate to first order in the volume fraction f. Short and long time limits of D(t) are checked against the known short time results for partially or fully absorbing boundary conditions and long time results for reflecting boundary conditions. For fully absorbing boundary condition the long time diffusion coefficient is found to be D(t)=5a(2)/(12fD(0)t)+O((D(0)t/a(2))(-2)) to the first order of perturbation theory. Here f is small but nonzero, D(0) the diffusion coefficient in the absence of spheres, and a the radius of the spheres. The validity of this perturbative result is discussed.     

"Single sample concept": theoretical model for a combinatorial approach to solid-state inorganic materials

A theoretical model for a "single sample concept" (SSC) applied to the combinatorial chemistry of solid-state inorganic compounds is presented. The SSC is performed by reacting N starting materials (randomly mixed) in a single sample of approximately 1 cm(3). Combinatorial calculations demonstrate that the number of reasonably estimated phases to be found in the space of N components grouped into compounds (e.g. oxides, sulfides, or halogenides) containing up to q < or = 6 metallic elements is smaller than combinations set up by starting conditions for local reactions within the bulk of a single ceramic sample. Recently, the SSC proved to work in the case of synthesizing libraries of 3d metal oxides, from which magnetic particulate matter was extracted by a magnetic separation technique. The SSC may be applied in a first screening cycle followed by 2D approaches of combinatorial chemistry.     

Probing the lower limit of lattice thermal conductivity in an ordered extended solid: Gd117Co56Sn112, a phonon glass-electron crystal system

The discovery of novel materials with low thermal conductivity is paramount to improving the efficiency of thermoelectric devices. As lattice thermal conductivity is inversely linked to unit cell complexity, we set out to synthesize a highly complex crystalline material with glasslike thermal conductivity. Here we present the structure, transport properties, heat capacity, and magnetization of single-crystal Gd(117)Co(56)Sn(112), a complex material with a primitive unit cell volume of ~6858 ?(3) and ~285 atoms per primitive unit cell (1140 atoms per face-centered cubic unit cell). The room temperature lattice thermal conductivity of this material is κ(L) = 0.28 W/(m·K) and represents one of the lowest ever reported for a nonglassy or nonionically conducting bulk solid. Furthermore, this material exhibits low resistivity at room temperature, and thus represents a true physical system that approaches the ideal phonon glass-electron crystal.     

A "single-sample concept" (SSC): a new approach to the combinatorial chemistry of inorganic materials

Combinatorial estimations show that, within an unreacted ceramic sample prepared by mixing N different starting materials MxOy with average particle size approximately 1 microm, there are about 10(12) grains per cubic centimeter, sufficient for local reactions to occur that may produce a larger number of product oxides than presently accessible by 2D plate techniques. The "single-sample concept" (SSC) is proposed for performing property-directed syntheses for the preparation of ferri-/ferromagnetic or superconducting compounds. Because of the magnetic properties of the products, libraries of product grains can be sorted by means of magnetic separation techniques. For materials with a large magnetization, the separation efficiency is so high that traces of products can be isolated. The SSC concept was tested experimentally to prepare Fe-based oxides (N=17, 24, 30). The large yields (<75 wt %, N=17) of product grains agree with the literature data, which indicate that 3d metal magnetic oxide phases (Tc>300 K) are most probably Fe oxides. In combination with magnetic separation techniques, SSC seems particularly adapted for exploring the solid-state chemistry of metallic lead elements that form ferri-/ferromagnetic or superconducting oxide phases difficult to detect systematically within the large phase space of theoretically existing compounds.     

Optical sensors with molecularly imprinted nanospheres: a promising approach for robust and label-free detection of small molecules

Molecularly imprinted nanospheres obtained by miniemulsion polymerization have been applied as the sensitive layer for label-free direct optical sensing of small molecules. Using these particles as the sensitive layer allowed for improving response times in comparison to sensors using MIP layers. As a model compound, well-characterized nanospheres imprinted against l-Boc-phenylalanine anilide (l-BFA) were chosen. For immobilization, a simple concept based on electrostatic adsorption was used, showing its applicability to different types of surfaces, leading to a good surface coverage. The sensor showed short response times, good selectivity, and high reversibility with a limit of detection down to 60 μM and a limit of quantitation of 94 μM. Furthermore, reproducibility, selectivity, and long-term stability of the sensitive layers were tested. The best results were achieved with an adsorption on aminopropylsilane layers, showing a chip-to-chip reproducibility of 22%. Furthermore, the sensors showed no loss in signal after a storage time of 1 year.     

Photosynthetic reaction center mimicry of a "special pair" dimer linked to electron acceptors by a supramolecular approach: self-assembled cofacial zinc porphyrin dimer complexed with fullerene(s)

Biomimetic bacterial photosynthetic reaction center complexes have been constructed using well-defined self-assembled supramolecular approaches. The "special pair" donor, a cofacial porphyrin dimer, was formed via potassium ion induced dimerization of meso-(benzo-[15]crown-5)porphyrinatozinc. The dimer was subsequently self-assembled with functionalized fullerenes via axial coordination and crown ether-alkyl ammonium cation complexation to form the donor-acceptor pairs, mimicking the noncovalently bound entities of the photosynthetic reaction center. The adopted self-assembly methodology yielded supramolecular complexes of higher stability, with defined geometry and orientation. Efficient forward electron transfer from the singlet excited zinc porphyrin dimer to the fullerene entity and relatively slow reverse electron transfer, important steps in the photosynthetic light energy conversion have been achieved in these novel biomimetic model systems.     

Combining chemoenzymatic monomer transformation with ATRP: a facile "one-pot" approach to functional polymers

A facile "one-pot" chemoenzymatic-ATRP has been successfully developed through the combination of copper-catalytic ATRP and enzyme-catalytic monomer transformation reactions.     

Metal–insulator transition in the Hubbard model on a triangular lattice with disorders: Renormalization group approach

A multistages block renormalization group approach to study the metal–insulator transition in the Hubbard model on a triangular lattice with hexagonal blocks is presented and implemented. A second‐order phase transition with a critical point at U/t = 12.5 is obtained (the coupling parameters U and t correspond to the repulsive charging energy and to the nearest‐neighbor exchange coupling terms, respectively). In the presence of disorder the phase diagram for the system exhibits a metallic phase, an insulating phase, and a domain‐localized phase that separates them in the Mott regime. The subtle influence of electron–electron interactions upon inverse participation rate in the Anderson regime is also investigated. The results are discussed in light of experimental evidence for arrays of metalic quantum dots and exact numerical diagonalization of the Hubbard Hamiltonian. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 360–374, 2003     

Control of self-assembly of a 3-hexen-1,5-diyne derivative: toward soft materials with an aggregation-induced enhancement in emission

The supramolecular architectures of a fluorophore are controlled through the design of a conjugated polycatenar molecule, the self-assembly of which can be addressed toward a columnar liquid-crystalline phase and organogels. Thus, depending on the environmental conditions for self-assembly, compound CA9 organizes into an unprecedented hexagonal columnar mesophase in the condensed state, in which half a molecule constitutes the slice of the column, or into a rectangular mesomorphic-like organization in the presence of apolar solvents such as cyclohexane and dodecane, at a concentration in which fibers form and gelling conditions are fulfilled. In this Col(r)-type arrangement, the organization within the columns depends on the solvent. All of the materials prepared show luminescence, and moreover, a remarkable 3-fold increase in fluorescence intensity was observed in going from the solution to the gel state.     

Ab initio X‐ray structural characterization of an inclusion compound with a compositionally disordered chiral guest: no prior knowledge of the crystal composition

The crystal structure and absolute configuration of a molecular host/guest/impurity inclusion complex were established unequivocally in spite of our having no prior knowledge of its chemical composition. The host (4R,5R)‐4,5‐bis(hydroxydiphenylmethyl)‐2,2‐dimethyl‐1,3‐dioxolane, (I), displays expected conformational features. The crystal‐disordered chiral guest 4,4a,5,6,7,8‐hexahydronaphthalen‐2(3H)‐one, (II), is present in the crystal 85.1 (4)% of the time. It shares a common site with 4a‐hydroperoxymethyl‐4,4a,5,6,7,8‐hexahydronaphthalen‐2(3H)‐one, (III), present 14.9 (4)% of the time, which is the product of autoxidation of (II). This minor peroxide impurity was isolated, and the results of nuclear magnetic resonance, mass spectrometry, and X‐ray fluorescence studies are consistent with the proposed structure of (III). The complete structure was therefore determined to be (4R,5R)‐4,5‐bis(hydroxydiphenylmethyl)‐2,2‐dimethyl‐1,3‐dioxolane–4,4a,5,6,7,8‐hexahydronaphthalen‐2(3H)‐one–4a‐hydroperoxymethyl‐4,4a,5,6,7,8‐hexahydronaphthalen‐2(3H)‐one (1/0.85/0.15), C₃₁H₃₀O₄·0.85C₁₀H₁₄O·0.15C₁₀H₁₄O₃, (IV). There are host–host, host–guest, and host–impurity hydrogen‐bonding interactions of types S and D in the solid state. We believe that the crystals of (IV) were originally prepared to establish the chirality of the guest (II) by means of X‐ray diffraction analysis of host/guest crystals obtained in the course of chiral resolution during cocrystallization of (II) with (I). In spite of the absence of `heavy' elements, the absolute configurations of all anomeric centres in the structure are assigned as R based on resonant scattering effects.     

A novel approach toward the prediction of the glass transition temperature: Application of the EVM model,a designer QSPR equation for the prediction of acrylate and methacrylate polymers

We describe an original QSPR model called the EVM model (Energy, Volume, Mass) to calculate the glass transition temperature (T_g) of aliphatic acrylate and methacrylate homopolymers using classical molecular mechanics and dynamics. The latter was used to calculate an energy density function related to the cylindrical volume of a 20 monomer unit polymer segment (TSSV, Total Space around a Standard deviation Volume). We then calculated the T_g as a function of this density function and the repeat unit molecular weight, although no interchain interactions were taken into account. For linear and branched aliphatic acrylate and methacrylate polymers, the standard deviation from linear regression was 12 K, and the r² was 0.96. The model allows calculation of the T_g with an average absolute error of error of 10% for linear and branched derivatives not included in the original linear regression analysis. The results obtained with the EVM model are compared with those obtained with Bicerano's model. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2579–2590, 1997     

A simple approach toward low‐dielectric polyimide nanocomposites: Blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane

This article describes a new and simple method for preparing polyimide nanocomposites that have very low dielectric constants and good thermal properties: simply through blending the polyimide precursor with a fluorinated polyhedral oligomeric silsesquioxane derivative, octakis(dimethylsiloxyhexafluoropropyl) silsesquioxane (OF). The low polarizability of OF is compatible with polyimide matrices, such that it can improve the dispersion and free volume of the resulting composites. Together, the higher free volume and lower polarizability of OF are responsible for the lower dielectric constants of the PI‐OF nanocomposites. This simple method for enhancing the properties of polyimides might have potential applicability in the electronics industry. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6296–6304, 2008     

On the origin of a permanent dipole moment in nanocrystals with a cubic crystal lattice: effects of truncation, stabilizers, and medium for CdS tetrahedral homologues

A large anomalous dipole moment has previously been reported for nanocrystals with a cubic crystal lattice. By considering truncations of a regular tetrahedral CdS nanocrystal, the hypothesis that shape asymmetry is responsible for the observed dipole moment was tested and verified. The location and degree of the truncations were systematically varied, and corresponding dipole moments were calculated by using a PM3 semiempirical quantum mechanical algorithm. The calculated dipole moment of 50-100 D is in good agreement with a variety of experimental data. This approach also affords simple evaluation of the potential effect of the media for aqueous dispersions of nanocrystals. The substitution of the truncated corner(s) by molecules of H2O typically results in a substantial increase of the dipole moment, and often, in the reversal of its direction. The molecular modeling approach presented here is suitable for detailed theoretical studies of the dipole moments of II-VI and other nanoparticles and interparticle interactions in fluids. The data obtained from these calculations can be the starting point for modeling of agglomeration and self-organization behavior of large nanoparticle ensembles.     

Morphological evolution of inorganic crystal into zigzag and helical architectures with an exquisite association of polymer: a novel approach for morphological complexity

The morphology of potassium sulfate (K(2)SO(4)) crystals grown in a viscous polymer solution of poly(acrylic acid) (PAA) was remarkably changed from the tilted columnar assembly into zigzag and helical architectures with increasing PAA concentration. The habit modification of orthorhombic K(2)SO(4) with adsorption of PAA molecules on a specified crystal face fundamentally led to the formation of tilted unit crystals. Concurrently with the habit modification, a diffusion-limited condition controlling the assembly of tilted units was achieved in the presence of PAA molecules in the matrix. Various complex morphologies, including zigzag and helical assembly, emerged through the formation of twinned crystals with the variation of the diffusion condition. Understanding the morphogenesis observed in this report would provide a novel approach for sophisticated crystal design by using an exquisite association of organic and inorganic materials.     

Cyclometallated compounds of palladium(II) with a 2,4-pentanedionate: the X-ray crystal structure of

The behaviour of solutions containing 3-(N-tris[hydroxymethyl]methylamine)-2-hydroxypropanesulfonic acid (TAPSO) and copper(II) was studied by two analytical techniques, direct current polarography (DCP) and glass electrode potentiometry (GEP), at fixed total TAPSO to total copper(II) concentration ratios and various pH values, at 25 °C and ionic strength 0.1 M KNO₃. DCP and GEP, when used independently, were not able to provide a final metal-ligand model. Combined interpretation of data from DCP and GEP indicated the formation of six main species, CuL⁺, CuL(OH), CuL(OH)₂⁻, CuL₂, CuL₂(OH)⁻ and CuL₂(OH)₂²⁻ for which stability constants (as log β) were found to be 4.41, 11.43, 17.55, 8.08, 14.3 and 20.3, respectively. Five of these complexes, CuL(OH), CuL(OH)₂⁻, CuL₂, CuL₂(OH)⁻ and CuL₂ (OH)₂²⁻ are reported for the first time.     

Challenges in modelling and optimisation of stability constants in the study of metal complexes with monoprotonated ligands: Part I. A glass electrode potentiometric and polarographic study of a Cu-TAPSO-OH system

The behaviour of solutions containing 3-(N-tris[hydroxymethyl]methylamine)-2-hydroxypropanesulfonic acid (TAPSO) and copper(II) was studied by two analytical techniques, direct current polarography (DCP) and glass electrode potentiometry (GEP), at fixed total TAPSO to total copper(II) concentration ratios and various pH values, at 25 °C and ionic strength 0.1 M KNO₃. DCP and GEP, when used independently, were not able to provide a final metal-ligand model. Combined interpretation of data from DCP and GEP indicated the formation of six main species, CuL⁺, CuL(OH), CuL(OH)₂⁻, CuL₂, CuL₂(OH)⁻ and CuL₂(OH)₂²⁻ for which stability constants (as log β) were found to be 4.41, 11.43, 17.55, 8.08, 14.3 and 20.3, respectively. Five of these complexes, CuL(OH), CuL(OH)₂⁻, CuL₂, CuL₂(OH)⁻ and CuL₂ (OH)₂²⁻ are reported for the first time.     

Preparation,properties and x-ray crystal structure of a complex of bis(triphenylphosphoranylidene)ammonium iodide with 7,7,8,8-tetracyano-P-quinodimethane: (PPN)2(TCNQ)3(CH3CN)2

Bis(triphenylphosphoranylidene)ammonium iodide (PPN⁺I^?) forms a 2:3 complex with TCNQ [(PPN)₂(TCNQ)₃(CH₃CN)₂] that provides an example of a TCNQ complex containing acetonitrile in the crystal lattice; the material is a semi-conductor with trimerised TCNQ stacks.