Removal Of Water Molecules Research Articles

Formation of Silica Particles by Dc Voltage

In the present study, dc high voltage was applied to produce droplets with controlled diameter in wide range. The dc voltage was ranged from 0 to several kV. Water glass was atomized in alcohol solution into diameters of several ten μm, depending on dc voltage applied between nozzle and ground electrode. The atomized water glass droplets were solidified by removing water molecules from the water glass. When the dc voltage was raised, nozzle diameter and electrode distance were decreased, the diameter of silica particles was decreased.

The first observation of emission of electronically-excited states of the divalent Eu2+⁎ ion in the new chemiluminescent system EuCl3·6H2O–Bui2AlH–O2 and the energy transfer from Eu2+⁎ ion to the trivalent ion, Tb3+

We have discovered a new bright blue chemiluminescence (CL) in the title system, visible to the naked eye, caused by broadband fd emission of electronically-excited divalent europium ion, Eu2+⁎ (λmax=465nm). This is the first example in which a divalent lanthanide ion acts as a emitter and enhancer of liquid-phase CL. The CL was produced by adding the diisobutylaluminum hydride Bui2AlH to a suspension of EuCl3·6H2O crystalline hydrate in THF. Bui2AlH removes water molecules from the coordination sphere of Eu3+, and reduces Eu3+ to Eu2+. As a result, aluminoxane, isobutane, hydrogen and the complex EuCl2·(THF)x, where x≈2, are formed. And simultaneously excess of Bui2AlH is oxidized by oxygen traces generating a primary emitter, triplet-excited molecule, isobutyric aldehyde. The energy of the latter is transferred to the europium complex, EuCl2·(THF)x (x≈2), which emits blue light. The divalent Eu2+ ion is a much more efficient enhancer of CL in oxidation of Bui2AlH than the trivalent lanthanide ion Tb3+.

Highly photoluminescent Eu(III) complexes of the new 1-triphenylen-2-yl-3-trifluoroacetylacetone

The new triphenylene 1,3-diketone (1-triphenylen-2-yl-3-trifluoroacetylacetone (TphTA)) and its europium complexes were synthesized. The preliminary data on photophysical properties of Eu(TphTA)3(H2O)(C2H5OH) (1), Eu(TphTA)3(TOPO)(H2O) (2), Eu(TphTA)3(TOPO)2 (3) and Eu(TphTA)2NO3(TOPO)2 (4) are reported. Addition of a tri-n-octylphosphine oxide (TOPO) co-ligand to the europium diketonate complex removes water molecules from the coordination sphere, that leads to a significant increase of the photoluminescence quantum yield. The behavior of complexes 3 and 4 in nematic liquid crystal was investigated.

Structure of Alginate Gels: Interaction of Diuronate Units with Divalent Cations from Density Functional Calculations

The complexation of (1→4) linked α-L-guluronate (G) and β-D-mannuronate (M) disaccharides with Mg(2+), Ca(2+), Sr(2+), Mn(2+), Co(2+), Cu(2+), and Zn(2+) cations have been studied with quantum chemical density functional theory (DFT)-based method. A large number of possible cation-diuronate complexes, with one and two GG or MM disaccharide units and with or without water molecules in the inner coordination shells have been considered. The computed bond distances, cation interaction energies, and molecular orbital composition analysis revealed that the complexation of the transition metal (TM) ions to the disaccharides occurs via the formation of strong coordination-covalent bonds. On the contrary, the alkaline earth cations form ionic bonds with the uronates. The unidentate binding is found to be the most favored one in the TM hydrated and water-free complexes. By removing water molecules, the bidentate chelating binding also occurs, although it is found to be energetically less favored by 1 to 1.5 eV than the unidentate one. A good correlation is obtained between the alginate affinity trend toward TM cations and the interaction energies of the TM cations in all studied complexes, which suggests that the alginate affinities are strongly related to the chemical interaction strength of TM cations-uronate complexes. The trend of the interaction energies of the alkaline earth cations in the ionic complexes is opposite to the alginate affinity order. The binding strength is thus not a limiting factor in the alginate gelation in the presence of alkaline earth cations at variance with the TM cations.

Environmental effects in kelvin force microscopy of modified diamond surfaces

We have explored the effects of atmospheric environment on Kelvin force microscopy (KFM) measurements of potential difference between different regions of test polycrystalline diamond surfaces. The diamond films were deposited by microwave plasma-assisted chemical vapor deposition, which naturally produces hydrogen terminations on the surface of the films formed. Selected regions were patterned by electron-beam lithography and chemical terminations of oxygen or fluorine were created by exposure to an oxygen or fluorine plasma source. For KFM imaging, the samples were mounted in a hood with a constant flow of helium gas. Successive images were taken over a 5-h period showing the effect of the environment on KFM imaging. We conclude that the helium flow removes water molecules adsorbed on the surface of the samples, resulting in differences in surface potential between adjacent regions. The degree of water removal is different for surfaces with different terminations. The results highlight the importance of taking into account the atmospheric environment when carrying out KFM analysis.

Effect of Zn substitution on magnetic properties of nanocrystalline cobalt ferrite

The Zn substituted cobalt ferrite nanoparticles having the generic formula Co1−xZnxFe2O4 (x=0.0–0.7) were prepared by wet chemical coprecipitation technique using analytical reagent (AR) grade sulphates. The prepared samples were heated at 150 °C to remove water molecules and then annealed at 725 °C for 16 h. Investigation of the structural properties were carried out using x-ray diffraction, transmission electron microscopy (TEM), and scanning electron microscopy techniques. The nanocrystalline nature of the samples is confirmed by TEM data. Substitution of the nonmagnetic Zn2+ ions considerably changes the magnetic properties. Néel’s model fails to explain the observed magnetic behavior above x=0.2. For x≥0.2 the Yafet–Kittel model can be fitted. AC susceptibility measurements confirm the decrease in Curie temperature.

Ligand Migration and Cavities within Scapharca Dimeric HbI: Studies by Time-Resolved Crystallo- graphy, Xe Binding, and Computational Analysis

As in many other hemoglobins, no direct route for migration of ligands between solvent and active site is evident from crystal structures of Scapharca inaequivalvis dimeric HbI. Xenon (Xe) and organic halide binding experiments, along with computational analysis presented here, reveal protein cavities as potential ligand migration routes. Time-resolved crystallographic experiments show that photodissociated carbon monoxide (CO) docks within 5 ns at the distal pocket B site and at more remote Xe4 and Xe2 cavities. CO rebinding is not affected by the presence of dichloroethane within the major Xe4 protein cavity, demonstrating that this cavity is not on the major exit pathway. The crystal lattice has a substantial influence on ligand migration, suggesting that significant conformational rearrangements may be required for ligand exit. Taken together, these results are consistent with a distal histidine gate as one important ligand entry and exit route, despite its participation in the dimeric interface.

Dielectric liquid-in-liquid dispersion by applying pulsed voltage

Liquid-in-liquid dispersion, such as organic liquid in water or water in organic liquid, has been performed using dc or ac voltage applied between nozzle and ground electrode. In the present study, pulsed high voltage was applied to produce droplets with controlled diameter in wide range. The high voltage pulse source was capacitor discharge type with 20 - 50 Hz and ranged from 0 to several kV. Water glass was atomized in alcohol solution into diameters ranging from several mum to sub-mm, depending on applied voltage. The atomized water glass droplets were solidified by removing water molecules from the water glass. Synchronized droplet formation with pulse frequency was possible by controlling pulse voltage, width and frequency, which produced uniform sized droplets successively. When the pulse voltage was raised, the droplet formation mode changed from the synchronized formation to dispersion mode through transient mode. In the dispersion mode, droplets of several mum diameter having high uniformity were produced. Utilization of high voltage and high-speed pulse to liquid-liquid dispersion could make it possible to atomize in a conductive liquid without electrolysis.

The TiO2 nanoparticle effect on the performance of a conducting polymer Schottky diode

Among the conjugate polymers, poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate)(PEDOT:PSS) has been paid a great deal of attention for various applicationfields. The absorption intensity of the whole UV–visible range increases linearly,as the concentration of PEDOT:PSS increases. When a small amount ofTiO2 nanoparticles are dispersed in the PEDOT:PSS solution, the absorptionin the visible range normally increases, but the UV range absorption(TiO2 absorption area) is greatly depressed as the concentration of PEDOT:PSS increases. Various weight ratiosof TiO2 nanoparticles in PEDOT:PSS were prepared. TheTiO2/PEDOT:PSS solution was spin-coated onto the Al electrode and thermally treated to remove water molecules anddensify the film. These thermal processes generated nanocracks and nanoholes on the surface of theTiO2/PEDOT:PSS film. As the heating temperature increased, wider and longer nanocracks were generated.These nanocracks and nanoholes can be removed by subsequent coating and heatingprocesses. Schottky diodes were fabricated using four different concentrations ofTiO2–PEDOT:PSS solution. The forward current increased nearly two orders of magnitude by doping approximately 1%of TiO2 nanoparticles in PEDOT:PSS. Increasing theTiO2 nanoparticles in the PEDOT:PSS matrix, the forward current was continuouslyenhanced. The enhancement of forward current is nearly four orders ofmagnitude with respect to the pristine PEDOT:PSS Schottky diode. Thepossible conduction mechanisms were examined by using various plotting andcurve-fitting methods including a space-charge-limited conduction mechanism[Ln(J) versusLn(V)], Schottky emissionmechanism [Ln(J) versusE1/2], and Poole–Frenkelemission mechanism [Ln(J/V) versus E1/2]. Theplot of Ln(J)versus Ln(V) shows a linear relationship, implying that the major conduction mechanism is SCLC. As the concentrationof TiO2 increased, the conduction mechanism slightly detracted from the ideal SCLC mechanism.

An infrared spectroscopy study of the hydrogen bonding and water restructuring as a trisiloxane superspreading surfactant adsorbs onto an aqueous–hydrophobic surface

Trisiloxanes are surfactants with a compact trisiloxane group ((CH 3) 3Si–O–Si(CH 3)(C 3H 6– E j )–O–Si(CH 3) 3) as the nonpolar moiety and an oligomeric polyethylene oxide chain, E j ((OCH 2CH 2) j –R) as the polar group. (“R” is the cap of the polar group.) Trisiloxane surfactants with four to eight ethoxylates facilitate the rapid and complete spreading of drops of their aqueous solutions on very hydrophobic surfaces not otherwise wet by water. This superspreading ability, which is not completely understood, is unique to these amphiphiles in that solutions of conventional alkyl chain surfactants do not wet out on very hydrophobic surfaces. In this study, in an effort to understand the origin of superspreading, we use Fourier transform infrared spectroscopy in total attenuated internal reflection mode (FTIR-ATR) to gain a molecular picture of the adsorption of a trisiloxane surfactant onto an aqueous/hydrophobic-solid interface, and for comparison a nonsuperspreading alkyl chain surfactant. We focus on the OH stretch of water molecules to detail the changes in the hydrogen bonding structure of water at the interface, and methyl and methylene stretches to measure the adsorption densities. We compare the trisiloxane superspreader TE 8 ((CH 3) 3Si–O–Si(CH 3)((C 3H 6)(OCH 2CH 2) 8OH)–O–Si(CH 3) 3) with a conventional non-superspreading n-dodecyl polyoxyethylene glycol surfactant with the same ethoxylate chain length C 12E 8 (CH 3(CH 2) 11(OCH 2CH 2) 8OH), at concentrations below and above their critical aggregate concentrations. The spectra of C 12E 8 indicates that the adsorption removes the water molecules in the molecular layers in the vicinity the water/hydrophobic interface which have been shown to have a hydrogen bond coordination greater than those of bulk water. The trisiloxane spectra initially show this same behavior, but for longer times demonstrate the ability to remove water molecules which immediately straddle the surface with a dangling OH bond, and reconfigure them into a tightly hydrogen bonded network. This water restructuring is unobserved in the adsorption of the conventional surfactant, and, as it maximizes hydrogen bonding, is energetically favorable and may provide the enhanced driving force for adsorption and superspreading. Measurements of the adsorption densities provide additional information on how the architectures of the trisiloxane and polyethoxylate molecules determine the adsorption geometry and hydrogen bonding with water. From the measured surface densities at maximum adsorption we infer that the compact hydrophobic trisiloxane groups of the TE 8 molecules pack tightly along the hydrophobic surface where they exclude water molecules. This close packing is unimpeded by the oligomeric ethoxylate chain which is of equal cross-section as the hydrophobe, and extends into the aqueous phase within the hydrophobic footprint. In the case of C 12E 8, the measured densities at maximum packing indicate that the slender alkyl chain, while extending down to the hydrophobic surface, is spaced apart by the larger ethoxylate chain, thereby leaving water molecules immediately adjacent to the hydrophobic surface.

粘土鉱物モンモリロナイトへのアゾベンゼンの新規挿入法と分光学的評価

We tried to intercalate azobenzene into the interlayer spaces of montmorillonite by mixing fused azobenzene with solid montmorillonite after removing water molecules in the interlayer spaces by heating. The intercalation of azobenzene was confirmed by measuring the IR spectra and X-ray diffraction patterns. This is a new method of intercalation by use of the weak interaction between azobenzene and montmorillonite, which is different from previous methods of intercalation where either azobenzene is modified by an ionic substituent or montmorillonite is modified by an ionic surfactant. Reversible changes in the basal spacing of about 0.03-0.04 nm by UV or Vis irradiation were confirmed by the corresponding reversible changes in the electronic absorption spectra and the Xray diffraction patterns. A new model of intercalation is proposed, such that planar trans azobenzene molecules, which exist parallel to one another in the layers, dilate the interlayer by photoisomerization to non-planar cis azobenzene.

Punctual investigation of surface sites of HA and magnesium-HA

Abstract IR spectroscopy of adsorbed CO is used for the first time to characterize surface cationic centres of pure and magnesium doped hydroxyapatite (HA and MHA, respectively). In air, water molecules saturate the coordination sphere of exposed surface cations by a strong coordinative interaction. At first, the materials were outgassed at 300 °C in order to remove water molecules adsorbed on the surface. Following this treatment, surface sites able to adsorb CO are produced. The vibrational frequency of adsorbed CO is sensitive to the features of the adsorbing sites. The IR spectra of CO adsorbed on HA revealed the presence of surface Ca2+ ions differing for the degree of coordinative unsaturation and of P OH groups. On MHA, CO was able to monitor the presence of surface Mg2+ ions, the amount of which increased by aging the material in air.

Application of model-free kinetics to the study of dehydration of fly ash-based zeolite

In the present paper, dehydration kinetics of zeolite Na-A synthesized from fly ash was investigated by means of thermogravimetric analysis. Na-A zeolite was formed from coal fly fash by fusion with sodium hydroxide and succeeding hydrothermal treatment at 100°C after induction period. The model-free kinetic method was applied to calculate the activation energy of the dehydration process of fly ash-based zeolite as a function of conversion and temperature. The Vyazovkin model-free kinetic method also enabled the definition of time, necessary to remove water molecules from the zeolite structure for a given temperature.

Effect of Surface Acidity of Al2O3 on Its Interactions with Lubricant Additives

The effect of the surface acidities of various aluminum oxides on the energy of adsorption of selective organic species has been studied by means of flow adsorption microcalorimetry. The strength of interaction of dioctyl sebacate (one typical lubricant additive) with the surface of Al2O3 depends on the amount of surface water and on the charge of surface hydroxide groups, with the positive and neutral charges being favorable. Temperature affects dioctyl sebacate adsorption by partially removing water molecules from the surface and exposing active sites, which then become available for adsorptive interactions. Al2O3 surfaces of various acidities have also been characterized using flow microcalorimetry and 1-butanol as a probe molecule. The adsorption capacity of 1-butanol on acidic Al2O3 is twice as much as that on the neutral and basic oxides.

Methodology and Problems of Protein‐Ligand Docking: Case Study of Dihydroorotate Dehydrogenase, Thymidine Kinase, and Phosphodiesterase 4

The docking methodology was applied to three different therapeutically interesting enzymes: human dihydroorotate dehydrogenase (DHODH), Herpes simplex virus type I thymidine kinase (HSV1 TK) and human phosphodiesterase 4 (PDE4). Programs FlexX, AutoDock and DOCK where used. The three targets represent three distinct cases. For DHODH and HSV1 TK, the binding modes of substrate and inhibitors within the active site are known, while the binding orientation of cAMP within PDE4 has been solely hypothesized. Active site of DHODH is mainly hydrophobic and the binding mode of the inhibitor brequinar was used as a template for evaluating the docking strategies. The presence of cofactors revealed to be crucial for the definition of the docking site. The HSV1 TK active site is small and polar and contains crystal water molecules and ATP. Docking of thymidine and aciclovir (ACV) within the active site was analyzed by keeping or removing water molecules. It showed the crucial role of water in predicting the binding of pyrimidines and purines. The crystal structure of PDE4 contains magnesium and zinc cations as well as catalytic water molecule but no ligand. Several docking experiments of cAMP and rolipram were performed and the results showed clear‐cut dependence between the ligand orientation and the presence of metals in the active site. All three cases show specific problems of the docking methodology, depending on the character of the active site.

Preparation of todorokite-type manganese-based oxide and its application as lithium and magnesium rechargeable battery cathode

Todorokite type Mg x MnO 2· yH 2O which possesses 3×3 large tunnel structure was prepared through hydrothermal treatment of layer manganese dioxide, buserite, at 120–200°C. In non-aqueous Li and Mg cells, electrochemical insertion of Li + and Mg 2+ into the todorokite products occurred utilizing the preferable large tunnel for their diffusion. By heat-treatment up to 300°C, cycle performances in Li cell were improved by removing water molecules from the todorokite tunnel.

有機金属化学気相成長装置内の表面吸着水の高速除去

The chambers of Metal Organic Chemical Vapor Deposition (MOCVD) equipment are opened at regular intervals, in order to remove the by-products on the inner surface of the reactor chambers. After regular maintenance, it is difficult to remove water molecules adsorbed on the inner surface of chambers, so the through-put of wafers is difficult to improve. The purpose of this work is to present the method to remove adsorbed water molecules on the inner surface of chambers quickly. For this purpose, we use an in-situ and real-time moisture monitor based on near-infrared laser absorption spectroscopy and continuously measure the moisture concentration in MOCVD equipment exhaust gases at the experiment. It was clarified that the baking efficiency is improved by using the high thermal conductivity gases such as hydrogen (H2) gas and that the purge time is shorten by introducing trimethylaluminum (TMA) to purge gas under room temperature condition.

Deposition and characterization of Er+3-doped, Al co-doped sol-gel silica films on SOS

Up to 18 layers of crack-free Er-doped sol-gel silica films co-doped with Al were deposited on SOS (silica on silicon) by multiple spin-coating and rapid thermal processing (RTP). The properties of the films were studied using ellipsometry, FTIR (Fourier Transform Infrared) Spectroscopy, AFM (atomic force microscopy) and XRD (X-ray diffraction). The results showed that, compared with air environment, a moderate (45–50 mbar) vacuum annealing environment could remove water molecules (H2O) in the prepared film more effectively and yield smoother film surface.

Studies of cation binding in ZnCl2-regenerated bacteriorhodopsin by x-ray absorption fine structures: effects of removing water molecules and adding Cl- ions

The binding of Zn2+ in Zn2+-regenerated bacteriorhodopsin (bR) was studied under various conditions by x-ray absorption fine structures (XAFS). The 0.9:1 and 2:1 Zn2+:bR samples gave similar XAFS spectra, suggesting that Zn2+ might have only one strong binding site in bR. It was found that in aqueous bR solution, Zn2+ has an average of six oxygen or nitrogen ligands. Upon drying, two ligands are lost, suggesting the existence of two weakly bound water ligands near the cation-binding site in bacteriorhodopsin. When excess Cl- ions were present before drying in the Zn2+-regenerated bR samples, it was found that two of the ligands were replaced by Cl- ions in the dried film, whereas two remain unchanged. The above observations suggest that Zn2+ has three types of ligands in regenerated bR (referred to as types I, II, and III). Type I ligands are strongly bound. These ligands cannot be removed by drying or by exchanging with Cl- ions. Type II ligands cannot be removed by drying, but can be replaced by Cl- ligands. Type III ligands are weakly bound to the metal cation and are most likely water molecules that can be removed by evaporation under vacuum or by drying with anhydrous CaSO4. The results are discussed in terms of the possible structure of the strongly binding site of Zn2+ in bR.

The Effect of The Initiator Heat Treatment Temperature on the Quality of Manganese Phosphate Coatings

SUMMARYThe work shows that the quality of phosphate coatings can be substantially improved by raising the heat treatment temperature during the synthesis of the initiator powder. Heat treatment removes water molecules from the hureaulite structure, increases the activity of manganese (II) ions and facilitates their partial substitution by iron (II) ions. The results suggest that ion substitution acts to stabilise the hureaulite initiators during phosphating and enhance the nucleation rate of phosphate crystals.