High Dielectric Constant Of Water Research Articles

Density functional theory study of Fe(CO)5 and [Fe(CO)6]2+ complexes catalyzed the water gas shift reaction extended to the aqueous phase

The WGSR with Fe(CO)5 and [Fe(CO)6]2+ complexes were investigated using DFT in both gaseous and aqueous phases. Thermodynamic analyses indicated that the high dielectric constant of water inhibits the activity of OH− and [Fe(CO)6]2+ ions, leading to a substantial decrease in the energy released during the nucleophilic attack of OH− on Fe(CO)5 and [Fe(CO)6]2+ in the aqueous phase. In addition, a potential low energy pathway has been discovered by designing new transition states for the final step of Fe(CO)5-catalyzed WGSR: 1 → 6 → 2 → 3 → 4 → 5(a) → 5(b) → 6. According to the results of the ESM, [Fe(CO)6]2+ possesses the highest gaseous phase TOF value (1.27×10−18 s–1), both Fe(CO)5 and [Fe(CO)6]2+ have higher TOF values in the gaseous phase compared to the aqueous phase, which increases with rising temperature. Therefore, these results suggest that [Fe(CO)6]2+ serves as the advantageous catalyst involved WGSR in the aqueous phase.

A computational design of X24Y24 (X = B, Al, and Y = N, P) nanoclusters as effective drug carriers for metformin anticancer drug: A DFT insight

• B 24 N 24 nanocluster can be a good candidate for the use of drug delivery systems compared whit Al 24 N 24 , Al 24 P 24 , and B 24 P 24 . • The high dielectric constant of water makes the nanocluster/drug complex in the aqueous solvent more stable than in the gas phase. • The amount of adsorption energies in the liquid phase was higher than the gas phase due to the presence of polar water solvent. • The drug molecule can be chemically adsorbed on the surface of nanoclusters with the negative amounts of Gibbs free energy and enthalpy. • It is expected that in an acidic environment, drug molecule binding to the nanocluster is getting weaker, thereby able to be released faster and benefits from a short recovery time. The present study aimed to investigate the adsorption of metformin (MF) drug on the boron nitride (B 24 N 24 ), aluminum nitride (Al 24 N 24 ), aluminum phosphide (Al 24 P 24 ), and boron phosphide (B 24 P 24 ) fullerene-like nanoclusters in the gas and solvent (water) at the B3PW91/6-311G(d, p) theoretical level. The anticancer MF drug can generally be adsorbed on the evaluated nanoclusters through its 5 N and 7 N in the imine functional groups. The polarizable continuum model (PCM) was used to investigate the solvent effects on the adsorption energies. The chemisorption of MF drug on the nanoclusters in all configuration states of A to H was observed with the adsorption energy above −0.6 eV in the gas and water environment. Comparison of the HOMO-LUMO energy gap in pure nanoclusters showed that the electronic properties of B 24 N 24 nanocluster compared to other nanoclusters studied can be enhanced by doping with aluminum and phosphorus atoms. Thermodynamic analysis showed that the interaction between MF and nanoclusters is exothermic and spontaneous. Among all drug adsorption states on the tested nanoclusters, state A in the B 24 N 24 nanocluster showed the highest reduction in HOMO-LUMO energy gap (∼20%) and the shortest recovery time (∼39 ms under UV radiation). Therefore, it is predicted that the B 24 N 24 nanoclusters could be industrially developed as a drug delivery system for MF.

Enabling Better Electrochemical Activity Studies of H2O‐Soluble Au Clusters by Phase Transfer and a Case Study of Lipoic‐Acid‐Stabilized Au22

AbstractIn stark contrast to organic systems, insight of the electrochemical properties is rather limited in aqueous solution for Au clusters, which have received extensive research attention recently. We demonstrate phase transfer as an efficient strategy to shuttle the Au nanoclusters between aqueous and organic solvents cyclically. The ability to phase transfer the Au clusters circumvents the limitations of potential window and high dielectric constant of water for electrochemistry studies. Two types of ligand molecular structures were employed with different hydrophilicity/hydrophobicity: mercaptosuccinic acid and lipoic acid, the latter featuring a longer hydrophobic portion and disulfide group (for Au bonding). The transfer efficiency was evaluated at different pHs. Additional redox activities from the Au22LA12 cluster that could not be seen from aqueous measurements were successfully resolved. Reversible and controllable transfer between aqueous and organic phases is believed to be a generalizable approach that could enable broader applications.

On-chip Feedthrough Cancellation Technique for Enhanced Electrical Characterization of a Piezoelectric MEMS Resonator in Water

In this work, we report a unique on-chip approach of cancelling feedthrough applied to a Thin-film Piezoelectric-on-Silicon (TPoS) MEMS resonator fully immersed in deionized (DI) water to enhance the signal-to-background ratio (SBR) in the context of full electrical characterization. We experimentally validate the proposed technique by demonstrating an SBR as high as 25dB despite a reasonably low quality factor (Q) of 162 and high dielectric constant of water from a reference SBR of 3.45dB. The proposed technique employs a pair of differential inputs where one input actuates the device while the other input cancels feedthrough and targets package-level parasitic elements associated with measuring in water. The resulting net feedthrough capacitance is reduced from 185fF to just 2.04fF in DI water. These results are based on a simple practical setup where the fabricated device is interfaced with a customized printed circuit board (PCB) by wire-bonds.

UV resonance Raman investigation of the aqueous solvation dependence of primary amide vibrations.

We investigated the normal mode composition and the aqueous solvation dependence of the primary amide vibrations of propanamide. Infrared, normal Raman, and UV resonance Raman (UVRR) spectroscopy were applied in conjunction with density functional theory (DFT) to assign the vibrations of crystalline propanamide. We examined the aqueous solvation dependence of the primary amide UVRR bands by measuring spectra in different acetonitrile/water mixtures. As previously observed in the UVRR spectra of N-methylacetamide, all of the resonance enhanced primary amide bands, except for the Amide I (AmI), show increased UVRR cross sections as the solvent becomes water-rich. These spectral trends are rationalized by a model wherein the hydrogen bonding and the high dielectric constant of water stabilizes the ground state dipolar (-)O-C═NH2(+) resonance structure over the neutral O═C-NH2 resonance structure. Thus, vibrations with large C-N stretching show increased UVRR cross sections because the C-N displacement between the electronic ground and excited state increases along the C-N bond. In contrast, vibrations dominated by C═O stretching, such as the AmI, show a decreased displacement between the electronic ground and excited state, which result in a decreased UVRR cross section upon aqueous solvation. The UVRR primary amide vibrations can be used as sensitive spectroscopic markers to study the local dielectric constant and hydrogen bonding environments of the primary amide side chains of glutamine (Gln) and asparagine (Asn).

Determination of saturated and unsaturated hydraulic conductivity using diviner 2000 capacitance probe

The estimation of hydraulic conductivity indicates how fluids flow through a substance and thus determine the water balance in the soil profile. In determining the saturated and unsaturated hydraulic conductivity of soil, five plots of 5.0 x 4.0 m were prepared with a PVC access tube installed in each plot. The plots were ponded profusely and surface covered with grass to prevent water loss by evaporation or water input by rain. The readings were taken twice daily for over a period of 5 days using capacitance probe with trade name Diviner 2000. The Diviner 2000 uses the method that utilizes the high dielectric constant of water compare to soil and air to determine water content of the soil. The trend lines of hydraulic conductivity has its linear regression r = 0.8296 - 0.9273 and its saturated hydraulic conductivity in the range of 5.09 cmh-1 – 14.03cmh-1 and unsaturated hydraulic conductivity in the range of 0.700 cmh-1 – 0.785 cmh-1. This reveals that soil water content can be obtained reasonably well from a capacitance probe which will allow for a determination of the pattern and use of the referred soil.

A comparative study of in-flow and micro-patterning biofunctionalization protocols for nanophotonic silicon-based biosensors

Reliable immobilization of bioreceptors over any sensor surface is the most crucial step for achieving high performance, selective and sensitive biosensor devices able to analyze human samples without the need of previous processing. With this aim, we have implemented an optimized scheme to covalently biofunctionalize the sensor area of a novel nanophotonic interferometric biosensor. The proposed method is based on the ex-situ silanization of the silicon nitride transducer surface by the use of a carboxyl water soluble silane, the carboxyethylsilanetriol sodium salt (CTES). The use of an organosilane stable in water entails advantages in comparison with usual trialkoxysilanes such as avoiding the generation of organic waste and leading to the assembly of compact monolayers due to the high dielectric constant of water. Additionally, cross-linking is prevented when the conditions (e.g. immersion time, concentration of silane) are optimized. This covalent strategy is followed by the bioreceptor linkage on the sensor area surface using two different approaches: an in-flow patterning and a microcontact printing using a biodeposition system. The performance of the different bioreceptor layers assembled is compared by the real-time and label-free immunosensing of the proteins BSA/mAb BSA, employed as a model molecular pair. Although the results demonstrated that both strategies provide the biosensor with a stable biological interface, the performance of the bioreceptor layer assembled by microcontact printing slightly improves the biosensing capabilities of the photonic biosensor.

Damage by radicals and photons during plasma cleaning of porous low-k SiOCH. II. Water uptake and change in dielectric constant

Porous dielectric materials provide lower capacitances that reduce RC time delays in integrated circuits. Typical low-k materials include porous SiOCH—silicon dioxide with carbon groups, principally CH3, lining the pores. With a high porosity, internally connected pores provide pathways for reactive species to enter into the material. Fluorocarbon plasmas are often used to etch SiOCH, a process that leaves a fluorocarbon polymer on the surface that must later be removed. During cleaning using Ar/O2 or He/H2plasmas,reactions of radicals that diffuse into the SiOCH and photons that penetrate into the SiOCH can remove –CH3 groups. Due to its higher reactivity, cleaning with Ar/O2plasmas removes more –CH3 groups than He/H2 plasmas, and so produce more free radical sites, such as –SiO2• (a –SiO2–CH3 site with the –CH3 group removed).Upon exposure to humid air, these free radical sites can chemisorb H2O to form hydrophilic Si–OH which can further physisorb H2O through hydrogen bonding to form Si–OH(H2O). With the high dielectric constant of water, even a small percentage of water uptake can significantly increase the effective dielectric constant of SiOCH. In this paper, we report on results from a computational investigation of the cleaning of SiOCH using Ar/O2 or He/H2plasmas and subsequent exposure to humid air. The authors found that plasma cleaning with He/H2 mixtures produce less demethylation than cleaning with Ar/O2plasmas, as so results in less water uptake, and a smaller increase in dielectric constant. The water that produces the increase in dielectric constant is roughly half chemisorbed and half physisorbed, the latter of which can be removed with mild heating. Sealing the pores with NH3plasma treatment reduces water uptake and helps prevent the increase in dielectric constant.

In-lab and on-site measurements of hot mix asphalt density: Convergence and divergence hypotheses

The life cycle of hot mix asphalt (HMA) depends on the material density. Bulk specific gravity and air void content are crucial factors for quality control and quality assurance (QC/QA) procedures used to evaluate contract specifications. Densities measured in the laboratory are reliable and accurate but are obtained very slowly. On-site measurements are made using non-nuclear portable devices and are often considered biased and unreliable. The object of this work was to evaluate a proposed theoretical framework for interpreting in-lab and on-site measurements and to propose strategies for using non-nuclear portable devices in QC/QA. A decrease in porosity yielded in-lab specific gravities that converged. In contrast, due to the high dielectric constant of water the divergence of in-site measures was observed. A conceptual framework and two practical equations are provided.

Electrochemical synthesis of ZnO coatings from water–isopropanol mixed baths: control over oriented crystallization

Electroreduction of an aqueous solution of a soluble Zn salt results in the deposition of ZnO crystallites with hexagonal columnar morphology. The crystallites grow with their long axes normal to the substrate resulting in adherent coatings with a strong c-axis orientation. This phenomenon is on account of the polarity of the 001 crystal face combined with the high dielectric constant of water. When the dielectric constant of the solvent is changed by making a mixture of water and isopropanol, there is a change in the direction of orientation of the coating. The switch takes place in the sequence [001] → [102], [103] → unoriented → [100], [110] as the isopropanol concentration is raised in a step-wise manner to 60% (v/v). The switch in orientation is caused by the tilt of the long axes of the hexagonal columns of ZnO with respect to the normal to the substrate. Above 60% isopropanol concentration, ZnO deposition is suppressed. This work demonstrates solution-mediated control over oriented crystallization.

Utilizing the high dielectric constant of water: efficient synthesis of amino acid-derivatized cyclobutenones

This work reports the use of water as a solvent to facilitate an efficient syntheses of amino acid-derivatized cyclobutenone. Kinetics studies in different solvents reveals that high dielectric constants of the solvents are the primary attribute for the high yielding and fast rate for this reaction. This class of substitution reactions in water also proceeds efficiently with a wide range of amino acids.

Novel low voltage EHD spray nozzle for atomization of water in the cone jet mode

Due to the high surface tension and high conductivity, water is unsuitable for electrohydrodynamic (EHD) atomization using a DC electric field in air. The high local electric field, that is required to atomize water, is likely to generate corona discharge and consequently destabilize the atomization process. This study describes a novel low voltage EHD spray nozzle that can be used to atomize water and weak saline solutions in the stable cone jet mode. The properties of the atomization have been investigated together with the generated droplet size distribution. The nozzle operates at very low flow rates (0.5–4.0 μl/min). Due to the high dielectric constant of water and the low flow rate, the atomization takes place outside the applicability range of the scaling laws. The experimental results show that the droplet size is approximately constant when the flow rate is increased from 0.5 to 4.0 μl/min. The atomization of water was numerically simulated using computational fluid dynamics (CFD). The simulation results agree reasonably well with the experimental results with respect to the liquid cone shape and droplet size.

Suitable Paper for Erasable Toner and the Role of Water in the Erasing Process

The authors have revealed that paper having high smoothness, small pore size, and low drying ability is suitable for discoloring decolorable toner. In the heat erasing process, water accelerates the dissociation of leuco dye and developer and/or the diffusion of developer, considering the high dielectric constant of water and the solubility of developer in water. The authors have confirmed diffusion of the developer into paper from the toner in the heat erasing process by the direct evidence and results of energy dispersive x ray and time-of-flight-secondary ion mass spectrometry.

Calibration cell for E-field sensors in water environment

Compact and nonperturbing E-field sensors are used for antenna near field measurements. For application in the research area of hyperthermia these sensors are used in a water environment. Owing to the high dielectric constant of water in the frequency range from DC to ~1 GHz the sensitivity is changed. To perform a calibration of E-field sensors, a water-filled TEM-cell has been developed. The technique employs a transverse electromagnetic (TEM) transmission cell that operates as a 50 Ω impedance-matched system. A uniform TEM-field is established inside the cell.

A Capacitance Sensor with Planar Sensitivity for Monitoring Soil Water Content

AbstractA pair of isolated parallel wires in a frame were used as a capacitance sensor for soil water content determination. Due to the high dielectric constant of water, rising water content of th esoil between the wires increases the capacitance. As the frame and the wires have a horizontal position in the soil, no preferential vertical water flow is induced by the sensor. The total wire diameter of 1.1 mm and the separation of 2.5 mm leave enough space for undisturbed natural water flow. The sensitive volume has a thickness given by the wire separation of 2.5 mm and the open frame area of 5 by 5 cm. Measurements in two soil types (loamy sand and loamy silt) showed a rise of the capacitance from 15 to 65 pF when the water content increases from 0 to 0.45. A theoretical consideration exhibits the relationship between the measured dielectric constant εM and the volumetric water content θ given by εM = A(θ + Z)/(θ + N) with three parameters A, Z, and N depending only on the sensor geometry and dielectric constants. The corresponding fit function determined the parameters and approximated the calibration curve with a root mean square (RMS) deviation of 0.024, indicating the accuracy of the method. No significant difference in the εM‐θ relationship could be obtained between the two soils. Measurements with eight sensors at depths between 1 and 15 cm yield the time‐dependent water content profile with a resolution of 1 cm during the watering and drying of the soil.

Point specific measurement and monitoring of soil water content with an emphasis on TDR

During the past decade, a number of developments have improved the possibilities for real-time, in situ monitoring of soil water content, providing potential for much improved testing and validation of soil water models Brief reviews of the principles and procedures are presented for the gravimetric and gamma ray attenuation methods. A summary of the developments of time-domain reflectometry (TDR) demonstrates its high capability for continuous monitoring of soil water content. Portable dielectric probes (PDP) and capacitance instruments also use the high dielectric constant of water as an indicator of soil water content. Commercially available TDR instruments offer a choice of options that allow this method to be fitted to a variety of specific measurement requirements. The ease of use and portability of TDR instruments and the flexibility of design for the TDR probes has made possible the rapid measurement of surface and near surface water contents on a field scale. Multiplexers and data loggers now allow the efficient monitoring of water content to record both spatial and temporal patterns not previously detectable. Fine resolution and analyses within the electric field of a TDR probe has allowed us to measure and record the diurnal patterns of water uptake from, and its release to, relatively dry sod adjacent to growing corn roots Water distribution calculations show that the water measured as moving in and out of roots daily is sufficient to hydrate and stabilize the sheaths of soil that surround the root growing in dry soil. Key words: Soil water content, TDR, root uptake, root exudation, field measurement, water balance

Humidity and autoclave pressure effect on the interfacial shear strength of a microwave cured epoxy-glass fibre composite

Microwave radiation curing of thermoset composite has been shown to achieve higher strengths and stiffness than conventional thermal curing, due to a higher Interfacial Shear Strength (ISS). Industrial processing of critical composite components requires the application of additional pressure to reduce the final composite void content. The nucleation and growth of voids is dominantly driven by vaporisation of moisture content, which is particularly accelerated in the microwave process, due to the high dielectric constant of water. This paper examines the effect of humidity content and pressure on the Interfacial Shear Strength of a hot curing epoxy/fibre glass composite that was microwave cured. Results indicate that the ISS decreased with higher humidity % for different microwave power settings from 500–75 W. Application of a 8 bar pressure during cure increased the ISS values for all humidity levels significantly. This was attributed to the reduction in the interfacial voids, so that the effective interface between the fibre and matrix is increased.

Phospholipid interactions in model membrane systems. II. Theory

We describe statistical thermodynamic theory for the lateral interactions among phospholipid head groups in monolayers and bilayers. Extensive monolayer experiments show that at low surface densities, PC head groups have strong lateral repulsions which increase considerably with temperature, whereas PE interactions are much weaker and have no significant temperature dependence (see the preceding paper). In previous work, we showed that the second virial coefficients for these interactions can be explained by: (a) steric repulsions among the head groups, and (b) a tilting of the P-N+ dipole of PC so that the N+ end enters the oil phase, to an extent that increases with temperature. It was also predicted that PE interactions should be weaker and less temperature dependent because the N+ terminal of the PE head-group is hydrophilic, hence, it is tilted into the water phase, so dipolar contributions among PE's are negligible due to the high dielectric constant of water. In the present work, we broaden the theory to treat phospholipid interactions up to higher lateral surface densities. We generalize the Hill interfacial virial expansion to account for dipoles and to include the third virial term. We show that to account for the large third virial coefficients for both PC and PE requires that the short range lateral attractions among the head groups also be taken into account. In addition, the third virial coefficient includes fluctuating head group dipoles, computed by Monte Carlo integration assuming pairwise additivity of the instantaneous pair potentials. We find that because the dipole fluctuations are correlated, the average triplet interactions do not equal the sum of the average dipole pair potentials. This is important for predicting, the magnitude and the independence of temperature of the third virial coefficients for PC. The consistency of the theory with data of both the second and the third virial coefficients extends the applicability of the head-group model to semiconcentrated monolayers, in agreement with the surface potential data in the foregoing paper.

Electrophoresis of small particles and fluid globules in weak electrolytes

The electrical double layer plays an essential role in the electrokinetic behavior of both rigid and fluid spheres. One of the assumptions woven into the formulation of the classical balance laws of electrokinetics is that the ionogenic solutes are fully ionized. In aqueous media, common inorganic electrolytes such as KCl and NaOH dissociate completely into their constituent ions; the high dielectric constant of water favors dissociation by lowering the energy required to ionize a solute. Not all ionic solutions are aqueous, however, and electrokinetic effects are important in these media, too. Less polar liquids have a much lower dielectric constant, and so they are unable to sustain a high degree of solute ionization; in fact ionogenic solutes may dissociate less than a percent. Here we examine the influence of partial ionization on the electrophoresis of small particles and fluid globules, with a view toward understanding how, and under what conditions, dissociation-association alters the electrokinetics. We find generally that mass-action, consistent with Le Chatelier's principle, works to minimize disturbances to the electrical double layer, resisting polarization of the diffuse ion cloud. Thus, dissociation-association processes are quantitatively important in cases where double layer polarization and relaxation would otherwise prevail. Consequently, the predicted impact on the electrophoretic mobility is greatest for drops and bubbles, since their surfaces are fluid and convection within the interface is a factor. Mass-action can reduce the mobility of a conducting drop by an order of magnitude, and sizeable decreases (50% and more) in drop mobility are even found at ζ-potentials below 50 mV. Rigid particles are affected less dramatically and quantitative effects rarely exceed 10%; particles are markedly insensitive to partial solute ionization unless the ζ-potential is high (above ca. 100 mV) and aκ > 1. The computation scheme employed applies strictly to situations in which the magnitude of the forcing-field is small. Nevertheless, the results imply that for electrokinetic phenomena driven by strong forcing-fields, dissociation-association processes involving ionogenic solutes may be significant in apolar liquids.

The dielectric constant of water: influence of the quadrupole moment

We examine the suggestion that the very high dielectric constant of water is associated with the absence of a significant component of the quadrupole tensor along the direction of the dipole moment. We find that although ⊖ zz ≈ 0, there is a large “effective axial” moment ⊖ eff zz.