EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2009
Cristina Núñez
Abstract Lanthanide complexes of a hexaaza macrocyclic ligand containing a pyridine head unit (L) were synthesized (Ln = La,Lu, except Pm). The solid-state structures of the corresponding La, Ce, Pr, Nd, and Lu complexes were determined by single-crystal X-ray crystallography, and they reveal the presence of three different mononuclear complexes with three different conformations of the macrocycle and coordination environments around the metal ions. In all complexes the lanthanide ion is coordinated in an endomacrocyclic manner to the six nitrogen donor atoms of the ligand. In the La, Ce, and Pr complexes the metal ions show a 12-coordinate mononuclear environment in which 3 nitrate anions coordinate in a bidentate fashion. However, in the Nd analogue the metal ion displays a 10-coordinated environment with the coordination of 2 bidentate nitrate groups, whereas Lu shows a 9-coordinate environment interacting with 2 nitrate ligands, one of them acting as bidentate and the second one coordinating in a monodentate fashion. The 1H and 13C NMR spectra of the complexes recorded in CD3CN suggest that the complexes adopt in solution a similar structure to that observed for the Nd complex in the solid state. The [Ln(L)(NO3)3] and [Ln(L)(NO3)2]+ complexes were characterized by density functional theory (DFT) calculations (B3LYP model). The structures obtained from these calculations for La, Ce, Pr, and Nd are in good agreement with the experimental solid-state structures. The relative stabilities of the [Ln(L)(NO3)2]+ complexes with respect to the [Ln(L)(NO3)3] ones (Ln = La, Nd, Gd, Ho, or Lu) were studied both in vacuo and in acetonitrile solution (PCM model) at the same computational level. Our calculations indicate that in solution the [Ln(L)(NO3)2]+ species is the most stable one along the whole lanthanide series, in agreement with the NMR spectroscopic data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Solid-State Adducts between C60 and Decamethylferrocene

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2003
Aldo Arrais
Abstract Co-deposition from concentrated solutions of C60 and Fe[C5(CH3)5]2 affords two solid products in different yields. The major product 1, in the form of regular shaped crystals, has been investigated by X-ray diffraction, 13C CPMAS NMR and vibrational spectroscopy, which showed it to be a co-crystalline adduct of C60 and Fe[C5(CH3)5]2 with no significant electron charge transfer between the two building blocks. The minor product 2, in the form of an amorphous powder, has been investigated by vibrational techniques. Both IR and Raman spectra are consistent with a solid structure in which electron transfer between the two units appears to be possible. ((© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Solid-State and Solution Structural Studies of 4-{[C(E)]-1H -Azol-1-ylimino)methyl}pyridin-3-ols

HELVETICA CHIMICA ACTA, Issue 7 2006
Dionisia Sanz
Abstract The new N -salicylideneheteroarenamines 1,4 were prepared by reacting the biologically relevant 3-hydroxy-4-pyridinecarboxaldehyde (5) with 1H -imidazol-1-amine (6), 1H -pyrazol-1-amine (7), 1H -1,2,4-triazol-1-amine (8), and 1H -1,3,4-triazol-1-amine (9). Solution 1H-, 13C-, and 15N-NMR were used to establish that the hydroxyimino form A is the predominant tautomer. A combination of 13C- and 15N-CPMAS-NMR with X-ray crystallographic studies confirms that the same form is present in the solid state. The stabilities and H-bond geometries of the different forms, tautomers and rotamers, are discussed by using B3LYP/6-31G** calculations. [source]

Solid-State Induced Heterocyclization under Microwave Irradiation: Synthesis of 2-Phenyl-3-hydroxy-quinolin-4(1H)-one (IV).

CHEMINFORM, Issue 26 2006
Majid M. Heravi
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Solid-State and Solution Studies of {Lnn(SiW11O39)} Polyoxoanions: An Example of Building Block Condensation Dependent on the Nature of the Rare Earth.

CHEMINFORM, Issue 24 2003
Pierre Mialane
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Pentacene-Based Polycyclic Aromatic Hydrocarbon Dyads with Cofacial Solid-State ,-Stacking

CHEMISTRY - A EUROPEAN JOURNAL, Issue 46 2009
Dan Lehnherr
Give me five! Pentacene-based polycyclic aromatic hydrocarbon (PAH) dyads are synthesized via an unsymmetrical pentacene building block. These molecules exhibit cofacial solid-state ,-stacking as a result of the large aromatic chromophores. The choice of the PAH attached to the pentacene (see picture) influences the electronic properties as determined by UV/Vis absorption/emission spectroscopy and cyclic voltammetry. [source]

TROSY effects in MAS solid-state NMR

CONCEPTS IN MAGNETIC RESONANCE, Issue 2 2008
Veniamin Chevelkov
Abstract Use of transverse relaxation-optimized spectroscopy (TROSY) type techniques had a dramatic impact on the study of large proteins with a molecular weight >30kDa for solution-state NMR. In the solid-state, such an effect would not be expected a prior, as the investigated molecules are immobilized. However, local motions induce fluctuations of the local fields experienced by the nuclear spins and, this way, are effective for relaxation. We demonstrate that protein dynamics can significantly influence the resonance line width in ultra high resolution MAS (magic angle spinning) solid-state NMR experiments. Averaging of the 15NH,/, multiplet components as a consequence of 1H decoupling induces effective broadening of the 15N resonance. Application of TROSY type techniques that select only the narrow component of the multiplet pattern results in an increased resolution and, thus, will be of benefit for MAS solid-state NMR spectroscopy. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part A 32A: 143,156, 2008. [source]

Spin-lattice relaxation of spin-½ nuclei in solids containing diluted paramagnetic impurity centers.

CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003

Abstract Dynamic nuclear polarization of nuclear spins via the solid-state and thermal mixing effects is discussed. Continuous-wave S- and X-band microwave radiation have been employed to measure 13C signal enhancements and polarization times for 13C nuclei in a natural type Ib diamond as a function of magnetic field. It was found that thermal mixing plays an important role in the 13C signal enhancement because the central electron spin resonance (ESR) line width HL , H0,C/,e, resulting in flip-flip and flip-flop forbidden transitions taking place simultaneously. On the other hand, the 13C spin-lattice relaxation rate is determined to a large extent by the solid-state effect (forbidden transitions). 13C polarization rates have also been measured for a suite of natural diamonds. It is shown that the polarization rate is proportional to the paramagnetic impurity concentration, in agreement with the theory. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 19A: 36,43, 2003. [source]

Tris(2,2,-bipyridyl)ruthenium(II) Electrogenerated Chemiluminescence Sensor Based on Platinized Carbon Nanotube,Zirconia,Nafion Composite Films

ELECTROANALYSIS, Issue 12 2010
Hyun Yoon
Abstract Mesoporous films of platinized carbon nanotube,zirconia,Nafion composite have been used for the immobilization of tris(2,2,-bipyridyl)ruthenium (II) (Ru(bpy)32+) on an electrode surface to yield a solid-state electrogenerated chemiluminescence (ECL) sensor. The composite films of Pt,CNT,zirconia,Nafion exhibit much larger pore diameter (3.55,nm) than that of Nafion (2.82,nm) and thus leading to much larger ECL response for tripropylamine (TPA) because of the fast diffusion of the analyte within the films. Due to the conducting and electrocatalytic features of CNTs and Pt nanoparticles, their incorporation into the zirconia,Nafion composite films resulted in the decreased electron transfer resistance within the films. The present ECL sensor based on the Pt,CNT,zirconia,Nafion gave a linear response (R2=0.999) for TPA concentration from 3.0,nM to 1.0,mM with a remarkable detection limit (S/N=3) of 1.0,nM, which is much lower compared to those obtained with the ECL sensors based on other types of sol-gel ceramic,Nafion composite films such as silica,Nafion and titania,Nafion. [source]

A New Donor-Stabilized Ditungsten Amido Alkoxido Species: Synthesis, Crystal Structure, Fluxionality, and Grafting onto Silica

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2007
Olivier Coutelier
Abstract A new dimeric tungsten(III) complex containing amidoand chelating pyridine,alkoxido ligands was synthesized through protonolysis of [W2(NMe2)6] by 2-(2-pyridyl)propan-2-ol and fully characterized by X-ray diffraction and infrared and NMR spectroscopy. Intramolecular exchange processes were studied by variable-temperature NMR spectroscopy. The compound was grafted onto dehydroxylated silica by protonolysis of an amido,tungsten bond, and the structure of the supported species was investigated by infrared and solid-state (bidimensional) NMR spectroscopy. The reactivity of the molecular and grafted species toward alkynes was probed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Conformational Flexibility in a Carbobicyclic Diphosphinite Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2007
Ian J. S. Fairlamb
Abstract An unsymmetrical bicyclo[3.2.0]heptanyl diphosphinite ligand, FLEXIphosO, shows flexible coordination modes to palladium centres. The X-ray crystal structure for [Pd02(P,P,)3] has been determined which reveals that the bicyclic backbone of the FLEXIphosO ligand exists in an exo -envelope conformation. The change in conformation stands in stark contrast to that observed in mononuclear neutral and cationic palladium(II) complexes containing the FLEXIphosO ligand, where an endo -envelope is observed in solution and in the solid-state. Theoretical studies provide an insight into the relative stability of palladium(0) complexes containing the FLEXIphosO ligand. Another large spanning angle ligand, SPANphos, does not form a similar palladium(0) dimer complex under identical reaction conditions, highlighting the unusual behaviour of the FLEXIphosO ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Studies of Pyridinyl-Containing 14-Membered Macrocyclic Copper(II) Complexes

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2003
Sabrina Autzen
Abstract Six copper(II) complexes of tetracoordinating, pyridinyl-containing 14-membered macrocycles with varying ratios of nitrogen and oxygen donor atoms were prepared and characterized by IR, UV/Vis, and EPR spectroscopy and cyclic voltammetry. A distorted tetragonal coordination of the copper center in the solid-state was established by X-ray crystallography for the tetraazamacrocyclic complex Cu-3 carrying a methoxybenzyl pendent arm and the trioxaaza complex Cu-6. The superoxide dismutase-like activity of the CuII complexes was investigated by inhibition of NADH oxidation. Although the UV/Vis and EPR spectra of the complexes were strongly affected when the coordinating nitrogen atoms were successively replaced by oxygen atoms, no significant change in their reactivity towards superoxide was observed. In all cases a 1:1 or 1:2 stoichiometry for the reaction with superoxide was found, with the exception of the methoxybenzyl-substituted tetraaza complex, which showed a low catalytic activity with a turnover number of about 10. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Microstructure Evolution and Mechanical Properties of Linear Friction Welded 45 Steel Joint

ADVANCED ENGINEERING MATERIALS, Issue 8 2007
J. Ma
Linear friction welding (LFW) is an emerging solid-state joining process to extend the current applications of welding. The microstructure evolution and mechanical properties of LFW 45 steel joint were investigated. The microstructures from the weld center to the parent metal were the superfine ferrite+pearlite in the weld center, the deformed fine ferrite + pearlite in the thermomechanically affected zone, the tempered sorbite, troosite and martensite in the heat affected zone. The microhardness of the joint decreased gradually from the parent metal to the weld center. The tensile properties of the joint were significantly improved in both the strength and ductility. The microstructure evolution, microhardness variation and fracture position are attributed to the various thermal histories of different positions. [source]

Control of Solid-State Dye-Sensitized Solar Cell Performance by Block-Copolymer-Directed TiO2 Synthesis

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
Pablo Docampo
Abstract Hybrid dye-sensitized solar cells are typically composed of mesoporous titania (TiO2), light-harvesting dyes, and organic molecular hole-transporters. Correctly matching the electronic properties of the materials is critical to ensure efficient device operation. In this study, TiO2 is synthesized in a well-defined morphological confinement that arises from the self-assembly of a diblock copolymer,poly(isoprene- b -ethylene oxide) (PI- b -PEO). The crystallization environment, tuned by the inorganic (TiO2 mass) to organic (polymer) ratio, is shown to be a decisive factor in determining the distribution of sub-bandgap electronic states and the associated electronic function in solid-state dye-sensitized solar cells. Interestingly, the tuning of the sub-bandgap states does not appear to strongly influence the charge transport and recombination in the devices. However, increasing the depth and breadth of the density of sub-bandgap states correlates well with an increase in photocurrent generation, suggesting that a high density of these sub-bandgap states is critical for efficient photo-induced electron transfer and charge separation. [source]

Enhanced-Light-Harvesting Amphiphilic Ruthenium Dye for Efficient Solid-State Dye-Sensitized Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
Mingkui Wang
Abstract A ruthenium sensitizer (coded C101, NaRu (4,4,-bis(5-hexylthiophen-2-yl)-2,2,-bipyridine) (4-carboxylic acid-4,-caboxylate-2,2,-bipyridine) (NCS)2) containing a hexylthiophene-conjugated bipyridyl group as an ancillary ligand is presented for use in solid-state dye-sensitized solar cells (SSDSCs). The high molar-extinction coefficient of this dye is advantageous compared to the widely used Z907 dye, (NaRu (4-carboxylic acid-4,-carboxylate) (4,4,-dinonyl-2,2,-bipyridine) (NCS)2). In combination with an organic hole-transporting material (spiro-MeOTAD, 2,2,,7,7,-tetrakis-(N,N -di- p -methoxyphenylamine) 9, 9,-spirobifluorene), the C101 sensitizer exhibits an excellent power-conversion efficiency of 4.5% under AM 1.5 solar (100 mW cm,2) irradiation in a SSDSC. From electronic-absorption, transient-photovoltage-decay, and impedance measurements it is inferred that extending the ,-conjugation of spectator ligands induces an enhanced light harvesting and retards the charge recombination, thus favoring the photovoltaic performance of a SSDSC. [source]

Aspergillus oryzae in solid-state and submerged fermentations

FEMS YEAST RESEARCH, Issue 2 2002
Progress report on a multi-disciplinary project
Abstract We report the progress of a multi-disciplinary research project on solid-state fermentation (SSF) of the filamentous fungus Aspergillus oryzae. The molecular and physiological aspects of the fungus in submerged fermentation (SmF) and SSF are compared and we observe a number of differences correlated with the different growth conditions. First, the aerial hyphae which occur only in SSFs are mainly responsible for oxygen uptake. Second, SSF is characterised by gradients in temperature, water activity and nutrient concentration, and inside the hyphae different polyols are accumulating. Third, pelleted growth in SmF and mycelial growth in SSF show different gene expression and protein secretion patterns. With this approach we aim to expand our knowledge of mechanisms of fungal growth on solid substrates and to exploit the biotechnological applications. [source]

DNA Sensing Using Nanocrystalline Surface-Enhanced Al2O3 Nanopore Sensors

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010
Bala Murali Venkatesan
Abstract A new solid-state, Al2O3 nanopore sensor with enhanced surface properties for the real-time detection and analysis of individual DNA molecules is reported. Nanopore formation using electron-beam-based decomposition transforms the local nanostructure and morphology of the pore from an amorphous, stoichiometric structure (O to Al ratio of 1.5) to a heterophase crystalline network, deficient in O (O to Al ratio of ,0.6). Direct metallization of the pore region is observed during irradiation, thereby permitting the potential fabrication of nanoscale metallic contacts in the pore region with application to nanopore-based DNA sequencing. Dose-dependent phase transformations to purely , and/or ,-phase nanocrystallites are also observed during pore formation, allowing for surface-charge engineering at the nanopore/fluid interface. DNA transport studies reveal an order-of-magnitude reduction in translocation velocities relative to alternate solid-state architectures, accredited to high surface-charge density and the nucleation of charged nanocrystalline domains. The unique surface properties of Al2O3 nanopore sensors make them ideal for the detection and analysis of single-stranded DNA, double-stranded DNA, RNA secondary structures, and small proteins. These nanoscale sensors may also serve as useful tools in studying the mechanisms driving biological processes including DNA,protein interactions and enzyme activity at the single-molecule level. [source]

Charge Generation and Photovoltaic Operation of Solid-State Dye-Sensitized Solar Cells Incorporating a High Extinction Coefficient Indolene-Based Sensitizer

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009
Henry J. Snaith
Abstract An investigation of the function of an indolene-based organic dye, termed D149, incorporated in to solid-state dye-sensitized solar cells using 2,2,,7,7,-tetrakis(N,N -di- p -methoxypheny-amine)-9,9,-spirobifluorene (spiro-OMeTAD) as the hole transport material is reported. Solar cell performance characteristics are unprecedented under low light levels, with the solar cells delivering up to 70% incident photon-to-current efficiency (IPCE) and over 6% power conversion efficiency, as measured under simulated air mass (AM) 1.5 sun light at 1 and 10,mW cm,2. However, a considerable nonlinearity in the photocurrent as intensities approach "full sun" conditions is observed and the devices deliver up to 4.2% power conversion efficiency under simulated sun light of 100,mW cm,2. The influence of dye-loading upon solar cell operation is investigated and the thin films are probed via photoinduced absorption (PIA) spectroscopy, time-correlated single-photon counting (TCSPC), and photoluminescence quantum efficiency (PLQE) measurements in order to deduce the cause for the non ideal solar cell performance. The data suggest that electron transfer from the photoexcited sensitizer into the TiO2 is only between 10 to 50% efficient and that ionization of the photo excited dye via hole transfer directly to spiro-OMeTAD dominates the charge generation process. A persistent dye bleaching signal is also observed, and assigned to a remarkably high density of electrons "trapped" within the dye phase, equivalent to 1.8,×,1017,cm,3 under full sun illumination. it is believed that this localized space charge build-up upon the sensitizer is responsible for the non-linearity of photocurrent with intensity and nonoptimum solar cell performance under full sun conditions. [source]

UV-vis-Induced Vitrification of a Molecular Crystal,

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2007
T. Naito
Abstract A charge-transfer complex of 2,5-dimethyl- N,N,-dicyanoquinonediimine (DM) with silver (crystalline Ag(DM)2, defined as ,) is irreversibly transformed by UV-vis illumination. Depending on the illumination conditions, three new types of solids (defined as ,, ,, and ,) with different structural and physical properties are obtained and examined by a variety of analytical techniques, including solid-state, high-resolution, cross-polarization magic angle spinning (CP-MAS) 13C,NMR, elemental analysis (EA), mass spectrometry (MS), X-ray absorption fine structure (XAFS), and powder X-ray diffraction (XRD). The CP-MAS, EA, MS, and XAFS results indicate that compound , is a glass state of Ag(DM)2. The transformation from crystalline (,) to amorphous (,) solid Ag(DM)2 is an irreversible exothermic glass transition (glass-transition temperature 155.2,°C; ,H,=,,126.8,kJ,mol,1), which implies that the glass form is thermodynamically more stable than the crystalline form. Compound , (Ag(DM)1.5) consists of silver nanoparticles (diameter (7,±,2),nm ) dispersed in a glassy matrix of neutral DM molecules. The N,CN,Ag coordination bonds of the , form are not maintained in the , form. Decomposition of , by intense illumination results in a white solid (,), identified as being composed of silver nanoparticles (diameter (60,±,10),nm). Physical and spectroscopic (XAFS) measurements, together with XRD analysis, indicate that the silver nanoparticles in both , and , are crystalline with lattice parameters similar to bulk silver; however, the magnetic susceptibilities differ from bulk silver. [source]

Bright and Efficient, Non-Doped, Phosphorescent Organic Red-Light-Emitting Diodes,

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2004
Y.-H. Song
Abstract Ir(III) metal complexes with formula [(nazo)2Ir(Fppz)] (1), [(nazo)2Ir(Bppz)] (2), and [(nazo)2Ir(Fptz)] (3) [(nazo)H,= 4-phenyl quinazoline, (Fppz)H,=,3-trifluoromethyl-5-(2-pyridyl) pyrazole, (Bppz)H,=,3- t -butyl-5-(2-pyridyl) pyrazole, and (Fptz)H,=,3-trifluoromethyl-5-(2-pyridyl) triazole] were synthesized, among which the exact configuration of 1 was confirmed using single-crystal X-ray diffraction analysis. These complexes exhibited bright red phosphorescence with relatively short lifetimes of 0.4,1.05,,s in both solution and the solid-state at room temperature. Non-doped organic light-emitting diodes (OLEDs) were fabricated using complexes 1 and 2 in the absence of a host matrix. Saturated red electroluminescence was observed at ,max,=,626,nm (host-emitter complex,1) and 652,nm (host-emitter complex,2), which corresponds to coordinates (0.66,0.34) and (0.69,0.31), respectively, on the 1931 Commission Internationale de l'Eclairage (CIE) chromaticity diagram. The non-doped devices employing complex,1 showed electroluminance as high as 5780,cd,m,2, an external quantum efficiency of 5.5,% at 8,V, and a current density of 20,mA,cm,2. The short phosphorescence lifetime of 1 in the solid state, coupled with its modest ,,, stacking interactions, appear to be the determining factors for its unusual success as a non-doped host-emitter. [source]

Secondary Metabolites from the Fungus Chaetomium brasiliense

HELVETICA CHIMICA ACTA, Issue 1 2008
Guo-You Li
Abstract Two new depsidones, mollicellins I and J (1 and 2, resp.), and a new chromone, 2-(hydroxymethyl)-6-methylmethyleugenin (3), along with six known compounds, 4,9, were isolated from the ethyl acetate extract of a solid-state fermented culture of Chaetomium brasiliense. Their structures were elucidated based on spectroscopic analysis. Mollicellins I and H (5) exhibited significant growth inhibitory activity against human breast cancer (Bre04), human lung (Lu04), and human neuroma (N04) cell lines with GI50 values between 2.5,8.6,,g/ml. [source]

Towards Optimization of Materials for Dye-Sensitized Solar Cells

ADVANCED MATERIALS, Issue 45 2009
Yanhong Luo
Abstract Dye-sensitized solar cells (DSCs) have received widespread attention owing to their low cost, easy fabrication, and relatively high solar-to-electricity conversion efficiency. Based on the nanocrystalline TiO2 electrode, Ru-polypyridyl-complex dye, liquid electrolyte with I,/I3, redox couple, and Pt counter electrode, DSCs have already exhibited an efficiency above 11% and offer an appealing alternative to conventional solar cells. However, further improvements in the efficiency and stability are still required to drive forward practical application. These improvements require the cooperative optimization of the component materials, structures, and processing techniques. In this Research News article, recent progress in DSCs made by our group are reviewed, including some novel approaches to the synthesis of solid-state and environmentally friendly electrolytes, the fabrication of alternative low-cost nanostructural electrodes, and the control of recombination at the interfaces. [source]

The Coming of Advanced Materials: A Personal View of the Contributions by Cambridge Scientists,

ADVANCED MATERIALS, Issue 38-39 2009
John Meurig Thomas
Abstract The highly significant contributions both directly and indirectly made to the study of condensed matter in general and to advanced materials in particular by a succession of Cambridge scientists over the early years of the past half century are adumbrated in the light of the conjunction of the 21st anniversary of the founding of this journal and the 800th anniversary of the University of Cambridge. So also are the reasons for the burgeoning growth in the last few decades of the preparation, characterization, and use of various kinds of advanced materials. A summary is also given of the author's own work in solid-state and materials science, including a brief appraisal of recent strategies for the design of advanced catalysts for the production (under environmentally benign conditions) of a number of industrially important chemicals ranging from vitamins to commodities, such as adipic acid and terephthalic acid, and building blocks, such as styrene oxide, that are utilized in the manufacture of cosmetics and perfumes. [source]

Cell growth and Trametes versicolor laccase production in transformed Pichia pastoris cultured by solid-state or submerged fermentations

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2010
Marcos López
Abstract BACKGROUND: Growth kinetics of Pichia pastoris and heterologous expression of Trametes versicolor laccase were compared. This is the first study of its kind between solid-state yeast cultures done on polyurethane foam (PUF) and submerged liquid fermentations (SmF). RESULTS: The maximum values of biomass were similar for SSF (solid-state fermentation) and SmF experiments when the BOD (biochemical oxygen demand) was lower than 100 g L,1. For higher BOD levels, the maximum values of biomass were 55 g L,1 (SSF) and 35 g L,1 (SmF). Micrographs of PUF preparations showed yeast growing within liquid lamellae, thinner than 100 µm, forming large horizontal aggregates. Yeast aggregates were much smaller in SmF than in SSF experiments; however, laccase expression was lower in PUF than in SmF, unless the methanol concentration was increased to 63 g L,1, which was inhibitory only to the SmF system. CONCLUSION: The results show that oxygen mass transfer is more efficient in SSF, which is related to the higher area/volume ratio compared with SmF. Induction differences may also be due to hindered diffusion of methanol within large yeast aggregates. Copyright © 2009 Society of Chemical Industry [source]

Origin of migmatites by deformation-enhanced melt infiltration of orthogneiss: a new model based on quantitative microstructural analysis

JOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2008
P. HASALOVÁ
Abstract A detailed field study reveals a gradual transition from high-grade solid-state banded orthogneiss via stromatic migmatite and schlieren migmatite to irregular, foliation-parallel bodies of nebulitic migmatite within the eastern part of the Gföhl Unit (Moldanubian domain, Bohemian Massif). The orthogneiss to nebulitic migmatite sequence is characterized by progressive destruction of well-equilibrated banded microstructure by crystallization of new interstitial phases (Kfs, Pl and Qtz) along feldspar boundaries and by resorption of relict feldspar and biotite. The grain size of all felsic phases decreases continuously, whereas the population density of new phases increases. The new phases preferentially nucleate along high-energy like,like boundaries causing the development of a regular distribution of individual phases. This evolutionary trend is accompanied by a decrease in grain shape preferred orientation of all felsic phases. To explain these data, a new petrogenetic model is proposed for the origin of felsic migmatites by melt infiltration from an external source into banded orthogneiss during deformation. In this model, infiltrating melt passes pervasively along grain boundaries through the whole-rock volume and changes completely its macro- and microscopic appearance. It is suggested that the individual migmatite types represent different degrees of equilibration between the host rock and migrating melt during exhumation. The melt topology mimicked by feldspar in banded orthogneiss forms elongate pockets oriented at a high angle to the compositional banding, indicating that the melt distribution was controlled by the deformation of the solid framework. The microstructure exhibits features compatible with a combination of dislocation creep and grain boundary sliding deformation mechanisms. The migmatite microstructures developed by granular flow accompanied by melt-enhanced diffusion and/or melt flow. However, an AMS study and quartz microfabrics suggest that the amount of melt present did not exceed a critical threshold during the deformation to allow free movements of grains. [source]

Water sorption induced transformations in crystalline solid surfaces: characterization by atomic force microscopy

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2010
Dabing Chen
Abstract The effect of water sorption on the mobility of molecules on the surface of a crystalline anhydrous solid was investigated to understand the mechanism of its transformation to the corresponding hydrate. Theophylline was chosen as the model compound. The transition water activity for anhydrate to hydrate transformation, RHT, and the deliquescence RH, RH0, was determined to be 62% and 99%, respectively (25°C). Atomic force microscopy (AFM) was used to study the surface changes of theophylline above and below the transition water activity. Contact-mode AFM showed that the jump-to-contact distance increased appreciably above RHT, suggesting formation of solution on the surface. At RHT,<,RH,<,RH0, using dynamic (AC/"tapping" mode) AFM, the movements of surface steps were visualized. These results from AFM indicated that, below RH0, the formation of a thin solution film significantly increased surface mobility. Furthermore, when the anhydrate crystal surface was seeded with the hydrate, the propagation of a new hydrate phase was observed by polarized light microscopy. In conclusion, atomic force microscopy provided direct evidence that the phase transformation of anhydrous theophylline to theophylline monohydrate in the solid-state is mediated by a surface solution as a result of water adsorption. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4032,4041, 2010 [source]

Solvent-free synthesis of pseudopolyrotaxane and polyrotaxane: Efficient threading complexation of a cyclodextrin wheel and a linear polymer axle to yield pseudopolyrotaxane and its fixation to polyrotaxane by the direct grinding of a solid mixture

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2007
Runtao Liu
Pseudopolyrotaxane was obtained through the grinding of a mixture of O -trimethyl-,-cyclodextrin and polytetrahydrofuran in a mortar by solvent-free synthesis, and it was fixed to stable polyrotaxane by a successive end-capping reaction with a bulky isocyanate by solid-state grinding in a mortar. Higher molecular weight polytetrahydrofurans (Mn > 1000) successfully produced corresponding polyrotaxanes in moderate yields and with moderate coverage ratios. O -Trimethyl-,-cyclodextrin and poly(ethylene glycol) also formed corresponding pseudopolyrotaxanes and polyrotaxanes by the grinding method. [source]

Preparation and characterization of poly(butylene terephthalate)/poly(ethylene terephthalate) copolymers via solid-state and melt polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2007
M. A. G. Jansen
Abstract To increase the Tg in combination with a retained crystallization rate, bis(2-hydroxyethyl)terephthalate (BHET) was incorporated into poly(butylene terephthalate) (PBT) via solid-state copolymerization (SSP). The incorporated BHET fraction depends on the miscibility of BHET in the amorphous phase of PBT prior to SSP. DSC measurements showed that BHET is only partially miscible. During SSP, the miscible BHET fraction reacts via transesterification reactions with the mobile amorphous PBT segments. The immiscible BHET fraction reacts by self-condensation, resulting in the formation of poly(ethylene terephthalate) (PET) homopolymer. 1H-NMR sequence distribution analysis showed that self-condensation of BHET proceeded faster than the transesterification with PBT. SAXS measurements showed an increase in the long period with increasing fraction BHET present in the mixtures used for SSP followed by a decrease due to the formation of small PET crystals. DSC confirmed the presence of separate PET crystals. Furthermore, the incorporation of BHET via SSP resulted in PBT-PET copolymers with an increased Tg compared to PBT. However, these copolymers showed a poorer crystallization behavior. The modified copolymer chain segments are apparently fully miscible with the unmodified PBT chains in the molten state. Consequently, the crystal growth process is retarded resulting in a decreased crystallization rate and crystallinity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 882,899, 2007. [source]

Dye-Sensitized Solar Cells Based on TiO2 Coatings with Dual Size-Scale Porosity

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2009
Lai Qi
Dye-sensitized solar cells (DSSC) with efficiencies greater than 4% were produced with templated "inverse opal" titania coatings. A novel one-step method produces uniform and crack-free coatings made using commercially available titania nanoparticles with high reproducibility and uniformity. In this research, a volatile solvent electrolyte was tested; however, it shows proof-of-concept that larger pore volumes can be created for increased penetration of more viscous electrolytes that can be utilized in high-efficiency cells. This dual size-scale porosity film is a promising structure for DSSC applications, especially for those solid-state or quasi-solid-state cells that require polymer electrolytes. [source]

Design of Ceramic Materials for Chemical Sensors: Effect of SmFeO3 Processing on Surface and Electrical Properties

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001
Hiromichi Aono
Perovskite-type SmFeO3 powders were prepared by the thermal decomposition of a heteronuclear complex, Sm(Fe(CN)6)·4H2O and by solid-state reaction between the corresponding single oxides, Sm2O3 and Fe2O3. The thermal decomposition behavior of the complex was studied by thermogravimetric analysis. X-ray diffractometry was used to investigate the structure of the products from the complex thermal decomposition and the formation of SmFeO3 from the oxide mixture. Powders prepared by both methods were used to deposit thick films onto alumina substrates with comb-type gold electrodes. The microstructure and chemical homogeneity of the film surfaces were investigated by scanning electron microscopy and Auger electron spectroscopy. Thick SmFeO3 single-phase films having a homogeneous elemental distribution on the surface were obtained when powder prepared by thermal decomposition of the complex was used for deposition, even when the powder was fired at low temperature (800°C). Surface chemical analysis was performed by X-ray photoelectron spectroscopy (XPS). The O 1s XPS line was deconvoluted into two peaks, attributed to adsorbed oxygen (Oad) and oxygen in the lattice (Olattice). Quantitative analysis showed that the surface coverage of iron, expressed as Fe/(Fe + Sm), was larger for the films prepared using the solid-state reacted powder. Although the Olattice/(Fe + Sm) atomic ratio was not influenced by the processing procedures (and, thus, by iron surface coverage), the amount of Oad decreased with increasing iron surface coverage. A model of the SmFeO3 surface was used to determine that the outermost layer of the perovskite-type SmFeO3 prepared from the complex consisted mainly of samarium ions that could each bond four adsorbed oxygen ions. A single oxygen ion could adsorb onto an iron ion, and therefore, the content of adsorbed oxygen was lower for the film prepared from the solid-state reacted powders, which showed larger iron surface coverage. Electrical conductance measurements, performed with increasing temperature in different gaseous environments, confirmed these findings. Higher conductances and lower activation energies were observed for the films with larger samarium surface coverage. [source]