New Regioselective Intercalation Reactions

Abstract

The ordered layered double hydroxide, [LiA1₂(OH)₆]CI. 2H₂O exhibits shape-selective ion-exchange intercalation of dicarboxylate anions. Specific isomeric preferences can be controlled by varying the reaction temperatures. The intercalated guests can be quantitatively recovered from the host lattice with concomitant regeneration of the host offering a novel approach in separation science. To illustrate the potential of this new material in separation science, we describe the isolation of pure 1,4-benzenedicarboxylate and 2, 6-naphthalenedicarboxylate from mixtures of their isomers. The neutral organic acids are both monomers in the synthesis of a range of important polyesters.     

The study on the phosphate glass melted by microwave irradiation

In this study, NH₄H₂PO₄, Li₂CO₃, and Ca(OH)₂ raw materials were mixed with and without adding water or pressing pressure. The three types of mixture (i.e., raw mixtures, waterish mixtures, and dense mixtures) were then subjected to microwave irradiation. The samples were characterized by various methods of analysis method. With adding water, the particles changed from irregularity into aggregation. Simultaneously, the existence of H₃PO₄ and increase in hydroxyl group of waterish mixtures is due to the decomposition of NH₄H₂PO₄, which could promote microwave absorption. In addition, dense mixtures could change into glass after microwave irradiation with increasing pressing pressure. The connection between mixtures with and without adding water or pressing pressure and degree of microwave absorption, and how they are influenced on glass formation is discussed.     

Effects of organic content and H2O/TEOS molar ratio on the porosity and pore size distribution of hybrid naphthaleneaminepropylsilica xerogel

The hybrid naphthaleneaminepropylsilica material was obtained by a sol-gel route, varying the organic loading and the water/TEOS molar ratio. Infrared spectroscopy was used to identify the organic and inorganic phases. The morphology of the hybrid material was studied by using scanning electron microscopy and N₂ adsorption-desorption isotherms. It was observed that the increase in the organic content produces a decrease in the size and volume of the pores as well as in the surface area of the xerogel. The best porosity was obtained for water/TEOS molar ratio between 4 and 6.     

Synthesis,growth and characterization of single crystals of pure and thiourea doped L‐glutamic acid hydrochloride

L(+)Glutamic acid hydrochloride [HOOC (CH₂)₂CH(NH₂) COOH·HCl], a monoamino dicarboxylic acid salt of L‐Glutamic acid was synthesized and the synthesis was confirmed by FTIR analysis. Solubility of the material in water was determined. Pure and Thiourea doped L‐Glutamic acid hydrochloride crystals were grown by low temperature solution growth using solvent evaporation technique. XRD, UV‐Vis‐NIR analyses were carried out for both pure and thiourea doped crystals. The crystals were qualitatively analyzed by EDAX analysis and the presence of thiourea was confirmed. The cell parameters of L‐Glutamic acid hydrochloride have been determined as a = 5.151 Å, b = 11.79 Å, c = 13.35 Å by X‐ray diffraction analysis and it crystallizes in orthorhombic space group P2₁2₁2₁. UV‐Vis‐NIR spectra analysis showed good optical transmission in the entire visible region for both pure and doped crystals. Micro hardness of both pure and doped crystals has been determined using Vickers micro hardness tester. The SHG efficiencies of both pure and doped crystals were determined using Kurtz powder test and pure L‐Glutamic acid hydrochloride crystal was found to possess better efficiency than thiourea doped L‐Glutamic acid hydrochloride crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mechanical and thermal properties of SiO2–PMMA monoliths

Organic–inorganic hybrid monoliths of cross-linked polymethylmethacrylate (PMMA) and silica (SiO₂) were prepared by sol–gel, using tetraethoxysilane (TEOS) and methylmethacrylate (MMA) as precursors and 3-(trimethoxysilyl) propylmethacrylate (TMSPM) to make compatible the organic and inorganic components. Two types of monoliths were prepared, H1-type using a molar ratio composition of 16:1:4 for water:TEOS:ethanol and 1:0.1:0.1 for TEOS:TMSPM:MMA and H2-type using 6.3:1:2.52 for water:TEOS:ethanol and 1:0.25:0.25 for TEOS:TMSPM:MMA. Semi-transparent monoliths were obtained in both cases after the gelation–solidification and drying processes, which took about seven days. Thermal properties of the samples were obtained by applying thermal lens spectroscopy and their mechanical properties were measured by depth sensing indentation and Vickers microhardness. FTIR spectroscopy measurements were performed to complement the characterization. We found that the hardness of the hybrid monoliths have values between those of commercial PMMA and a sol–gel SiO₂ monolith. This result is a consequence of the reinforcement produced by the SiO₂ component in the organic–inorganic hybrid matrix. The thermal diffusivity of the hybrid monoliths shows an appreciable increasing in the hybrid system with respect to the pure SiO₂ monolith. Mechanical behavior of monoliths is strong influenced by the SiO₂–PMMA ratio or changing the water:TEOS:ethanol contents.     

In situ studies of order–disorder phenomena in the synthesis of mesoporous silica

The initial hydrolysis of a silicon alkoxide in the presence of a suitable structural directing agent (template) so as to form a mesoporous silica powder exhibiting long-range hexagonal ordering was monitored using in situ XRD (X-ray diffraction), SAXS (small angle X-ray scattering) and SANS (small angle neutron scattering). The non-ionic triblock copolymer P123 (EO₂₀PO₆₉EO₂₀) was employed as the organic templating agent and tetramethoxysilane (TMOS) was used as the silica source in the presence of a water/acid catalyst. The synthesis method described herein is based around a high volume concentration ratio of surfactant to TMOS. The formation of a long-range mesoscopically ordered organic–inorganic hybrid that could be subsequently calcined to form a hexagonally structured mesoporous oxide material was monitored over 6 days using the characteristic (1 0 0) reflection. It was seen that during this ‘maturation’ period the reaction is not progressive and SANS and SAXS data together with XRD experiments show that there is an initial kinetically rapid organic ordering process which provides a template for the formation of an ordered metastable organic–inorganic oxide phase which then becomes progressively more disordered before a final kinetically slow stable long-range ordered phase is formed. Discussions of the origin of the unexpected order–disorder phenomena are made.     

Synthesis and Judd-Ofelt analysis of a sol-gel material doped with a Ln2(Benzoate)6(Phen)2 (Ln = Er/Yb) complex

In this work, we have prepared a sol-gel derived hybrid material directly doped with Er_1.4Yb_0.6(Benzoate)₆(Phen)₂ (Phen = 1,10-phenanthroline) complex, which was reported with intramolecular Yb-Er energy-transfer process in our previous work. The infrared (IR) spectra of the pure complex and hybrid gel material were investigated. The NIR photoluminescence (PL) spectrum of hybrid gel material shows strong characteristic emission of Er³⁺ with broad full width at half-maximum (FWHM) of 70 nm. Judd-Ofelt theory was used in order to analyze the optical properties of Er³⁺ ions in the hybrid gel material.     

Quenched glasses containing lanthanum and other trivalent sulfates

A wide glass-forming region has been observed in the Li₂SO₄-La₂(SO₄)₃ system with essentially pure glass produced by roller quenching compositions of 20 to 90% Li. Even water or air quenching produced glasses. Many of these glasses showed double exotherms during crystallization and some showed glass transitions. Limited experiments also showed some glass-formation in other alkali-La sulfates, in compositions containing Y and Sc sulfates and in mixtures. Ionic conductivities and some infrared measurements are also reported.     

Uniform TiO2 thin films with anatase nanocrystallites synthesized through evaporation-induced assembly

Uniform nanocrystalline anatase (nc-TiO₂) thin films have been synthesized in a ternary copolymer-ethanol–water system through evaporation-induced assembly (EIA) method. The EIA method combines sol–gel and organic–inorganic cooperative assembly technique. The resulting materials were characterized by X-ray diffraction, Fourier transform (FT) Raman spectroscopy, atomic force microscopy, scanning electron microscope, and ellipsometer measurements. The results showed uniform, spherical, and pure anatase crystallites were present in the calcined sample. Moreover, the prepared nc-TiO₂ thin films are smooth and exhibit crack-free nature. A reasonable formation mechanism of uniform nc-TiO₂ thin films is also presented in this work.     

Incorporation of Lithium into TiO2 Host and its Application in Photocatalysis

Abstract

In this work we prepared the stable photocatalyst by the incorporation of lithium into TiO₂ host. Lithium hydroxide was used as the modifier. Titanium host material was in two forms: commercial titanium dioxide (anatase. Police Chemical Factory, Poland) and titanium slurry that was slightly crystallized. The prepared materials have been characterized by XRD. FTIR and UV-Vis/DR methods. The XRD analysis showed that the main component of these samples was lithium titanate—Li₂TiO₃. The photocatalytic activity of prepared materials was tested in the photocatalytic reactions of oil and phenol decomposition in water. It was found that both oil and phenol undergo the photocatalytic decomposition over lithium-TiO₂ and the activity of these materials was higher in comparison with that of pure anatase host.     

Electrical conductivity and crystal structure of pure and SrCO3-doped Na2CO3

The electrical conductivity of pure and SrCO₃-doped sodium carbonate has been measured in the temperature range 310–800 °C in air using a dc technique. Its concentration dependency is similar to that of the K₂CO₃–SrCO₃ system described recently (GUTH et al. 1986). The maximum conductivity could be observed at ≈ 20 mol.% SrCO₃. At temperatures > 440 °C, the conductivity of Na₂CO₃–SrCO₃ mixtures containing up to 80 mol.% SrCO₃ is larger than that of pure Na₂CO₃. X-ray investigations of slowly cooled samples show the mixtures to be heterogeneous. X-ray diffraction patterns of quenched mixtures containing 10 mol.% SrCO₃ show reflexes of a high temperature compound. SrCO₃, however, could not be detected. The lattice constants of this hexagonal compound Na₂Sr₄(CO₃)₅ which is isotyp with Na₂Ca₂Sr₂(CO₃)₅ described by CHEN and CHAO are a₀ = (1066.1 ± 0.4) pm and c₀ = (653.2 ± 0.2) pm.     

Growth and high frequency dielectric study of pure and thiourea doped KDP crystals

Non linear optical (NLO) materials have acquired new significance with the advent of a large number of devices utilizing solid‐state laser sources. Several NLO materials have been used for this kind of technological applications. The Potassium di‐hydrogen phosphate (KDP) one of NLO material having superior non linear optical properties has been exploited for variety of applications. In the present investigation we have grown KDP crystals from aqous solution with thiourea, an organic non linear optical material. We could enhance the SHG efficiency of thiourea doped KDP crystal. It was 1.99 times more that of pure KDP. We observed more enhancements in nonlinearity for low concentration of thiourea.The crystal structure and cell parameters of grown crystal were determined from Powder XRD.The incorporation of thiourea in the grown crystals was qualitatively analyzed from FT‐IR study. The absorption spectra of pure and thiourea doped KDP crystal reveal that thiourea doped KDP crystals would be a better nonlinear optical (NLO) material for second harmonic generation (SHG) than pure KDP. The thermal decomposition and weight loss of pure and thiourea doped KDP crystal was observed by thermogravimetric (TGA) analysis and Differential Scanning Calorimetry (DSC). The high frequency dielectric study of pure KDP crystal, thiourea doped KDP crystals and organic additive thiourea was carried out using X‐band at frequency 8GHZ and 12GHZ by transmission line wave guide method. We observed low dielectric constant of thiourea doped KDP crystal when it is doped with 2mole% of thiourea. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrical Conductivity of Liquid Crystal Mixtures with Induced Smectic Phases

The electrical conductivity of the two liquid crystal mixtures N-(4-ethoxybenzylidene)-4′-amino benzonitrile (PEBAB)/4,4′-di-n-hexyloxy-azoxybenze (HEXOAB) and 4-n-heptyloxy-4′-cyanobiphenyl (7 CBP)/HEXOAB, which exhibit induced smectic A phases is investigated. In the smectic phases, the conductivity anisotropy of the PEBAB/HEXOAB mixtures is negative at the lowest PEBAB concentrations; this behaviour is usually expected for a smectic layer structure. With increasing PEBAB concentration the anisotropy increases and becomes positive. Possibly, this is an indication for a growing double layer structure, which was observed in polar smectic phases. In the nematic phases the conductivity anisotropy of the pure HEXOAB is considerably reduced by adding a relatively small amount of the polar component. An addition of 10 mole% 7 CBP reduces the anisotropy ratio of the electrical conductivity to V = K_∥/K ₁ ≈ 0.2, which probably is the lowest value observed in a nematic phase so far. Besides the negative conductivity anisotropy, these mixtures also exhibit a positive anisotropy of the dielectric constant. They thus fulfil the conditions for inverse dynamic scattering.     

Synthesis and characterization of PbI2 polycrystals

Single‐phase PbI₂ polycrystalline material for single crystal growth was synthesized by two‐temperature vapor‐transporting method (TVM), directly from highly pure lead and iodine with excess lead without according to the PbI₂ stoichiometry. It is found that there is an immiscible phenomenon of two melts in the synthesis experiment, and the melts solidified until cooled down to room temperature. X‐ray diffraction (XRD) analysis and Energy dispersive X‐ray (EDX) microanalysis indicate that the solidified materials are single‐phase PbI₂ polycrystal and nearly pure lead. Considering the observed immiscible phenomenon and the data given in paper [1], it is able to confirm that there is a new immiscible region L₂+L₃ in Pb‐I phase diagram, which is very important to PbI₂ polycrystal synthesis and single crystal growth. Using single‐phase PbI₂ polycrystalline material synthesized by our method, PbI₂ single crystal with size of ?15mm×30mm was grown by vertical Bridgman method. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Synthesis, spectroscopic characterization and X-ray structure determination of tetrabutylammonium trans-diamminetetranitrocobaltate(III)

The cobalt(III) complex salt [(C₄H₉)₄N][trans-Co(NH₃)₂(NO₂)₄] has been synthesized in high yield by reacting equimolar quantities of [(C₄H₉)₄N]Br and K[trans-Co(NH₃)₂(NO₂)₄] in aqueous medium at room temperature. The product thus formed has been re-crystallised from acetone-water mixture, in the monoclinic space group P 2₁/n, with cell dimensions a=11.651(3) ?, b=19.005(4) ?, c=11.733(5) ?, β=90.28(3)°. The X-ray structure determination revealed the presence of discrete ions, [(C₄H₉)₄N]⁺ and [trans-Co(NH₃)₂(NO₂)₄]⁻. The central metal ion cobalt(III) in the anion is found in octahedral environment, in trans geometry, while the organic counterion is a quaternary alkylammonium cation. The crystal lattice is stabilized by electrostatic interactions between the cations and anions.Supplementary material Crystallographic data (excluding structure factors) for the structure(s) reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC 291300. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (44) 1223 336-033; e-mail: deposit@ccdc.cam.ac.uk.     

Evolution of hierarchical‐structured CaCO3 in binary mixed solvent

Calcium carbonate with hierarchical structure was synthesized in water/organic compound binary soluvent by a chemical solution process within CaCl₂/NaCO₃ reaction system. Acetone, isopropanol, glycol, tetrahydrofuran were selected as the organic compound. Evolution of the hierarchical structure of CaCO₃ was investigated. The as‐prepared products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). CaCO₃ aggregations with spicate hierarchical structure were obtained with a high volume fraction of the organic solvent. Aspect ratio of the hierarchical structure increases to the highest when the volume fraction was 50%. Solvent with low dielectric constant was conducive to the oriented aggregation of the CaCO₃ grains.     

The Influence of Tribophysical Activation on Solid-State Reaction during Thermal Treatment of ZnO-Cr2O3

Tribophysical (mechanical) activation is used as a method for modification of physico-chemical properties of dispersed systems such as polycrystalline mixture of ZnO and Cr₂O₃ powders, obtained by conventional ceramic powder processing wet technique. Conventional mixtures were tribophysically activated by grinding in a vibro-mill with a continual regime in air. Conventional mixture and tribophysically activated mixtures, with activation times of 40 and 80 minutes, were thermally treated in non-isothermal and isothermal conditions. Solid-state reactions in non-isothermal conditions were examined by X-ray diffraction, differential thermal analysis and dilatometric measurements. The influences of tribophysical activation on solid-state reaction between ZnO and Cr₂O₃, during thermal treatment in isothermal conditions were investigated by X-ray diffraction line broadening theory. As a Fourier method for the pure physical line profile analysis a double-Voigt method is used. Mechanism of mass transport during solid-state reaction in ZnO-Cr₂O₃ system is proposed.     

On the deposition mechanism of boron in silicon CVD epitaxy

The deposition mechanism of boron doping in CVD silicon epitaxy has been investigated by exposing silicon substrates to B₂H₆ H₂ doping gas mixtures at epitaxy temperatures and examining the effect by dopant profile measuring in an afterwards intrinsically in-situ deposited epitaxial silicon layer. It has been shown that boron is deposited increasing its concentration on the surface linearly with prolonged exposition time and desorbed by purging the surface in pure hydrogen. In the latter case its content decreases linearly proportional to the predeposited concentration. The desorbed boron builds up a secondary doping source which maintains a parasitic boron flow for reincorporation during following layer growth.     

Crystal Growth and Structure of 4-Aminobenzophenone (ABP)

4-aminobenzophenone C₆H₅COC₆H₄NH₂ (ABP) is a good organic Nonlinear Optical (NLO) material. The bulk crystal has been grown by cooling method from organic solution, and the crystal structure determined by X-ray diffraction.     

The role of primitive relaxation in the dynamics of aqueous mixtures, nano-confined water and hydrated proteins

The relaxation scenario in aqueous systems, such as mixtures of water with hydrophilic solutes, nano-confined water and hydrated biomolecules, has been shown to exhibit general features, in spite of the huge differences in structure, chemical composition and complexity. Dynamics, in all these systems, invariably shows at least two relaxations: (i) a slower process, related to cooperative and structural motions of water and solute molecules (in the case of mixtures) or related to interfacial processes in the case of confined water and (ii) a faster process, with non-cooperative character originating from water. The latter has properties including timescale and temperature dependence similar or related in all the aqueous systems. This water-specific relaxation can be identified as the primitive relaxation, or the Johari-Goldstein β-relaxation. The primitive process is the precursor of the many-body relaxation process which increases in length-scale with time until the terminal α-relaxation is reached.Using new experimental data (at atmospheric and high pressure) along with a revision of most of the recent literature on the dynamics of confined water and aqueous mixtures, we show that the two abovementioned relaxation processes are inter-related as evidenced by correlations in their properties. For instance, both relaxation time and dielectric strength of the water-specific relaxation exhibit a crossover from a stronger to a weaker dependence with decreasing T, at the temperature where the slow process attains a very long timescale (> 1 ks) and becomes structurally arrested, exactly analogous to that found for β-relaxation in van der Waals liquids. Moreover, the primitive relaxation of water is shown to play a pivotal role in determining the dynamics of hydrated biomolecules in general, including the “dynamic transition” observed by neutron scattering and Mössbauer spectroscopy. We show that the primitive relaxation of the solvent is responsible for the dynamic transition, even in the case that the solvent is not pure water or an aqueous mixture.