Effect of amount of hydrated water and mobility of hydrated poly(2-methoxyethyl acrylate) on denaturation of adsorbed fibrinogen

In this study, a blood-compatible polymer, poly(2-methoxyethyl acrylate) (PMEA), was grafted onto a gold substrate with various grafting densities (σ) (σ = 0–0.18 chains nm⁻²), and the amount of hydrated water and mobility of the polymer chain interacting with water molecules were quantitatively evaluated using a quartz crystal microbalance with an admittance system. The amount of hydrated water decreased with increasing σ. By contrast, the mobility of the hydrated PMEA was maximum at σ ≈ 0.12 chains nm⁻², revealing that the amount of high-mobility water at σ = 0.12 was higher than that at other densities. The degree of denaturation of the adsorbed fibrinogen was evaluated based on the hydrodynamic water ratio and viscoelasticity, and was found to increase with increasing σ. The denaturation of adsorbed fibrinogen was suppressed when both the amount of hydrated water and the mobility of hydrated PMEA were high. This study demonstrates that the interfacial state of the polymer chains hydrated in water is important for blood compatibility.     

Reaction kinetics of hydrated electrons in a quaternary micro emulsion system: A pulse radiolysis study

The pulse-radiolysis technique has been employed to produce and study the kinetics of hydrated electrons (e_aq⁻) in a quaternary micro emulsion (Sodium Lauryl Sulfate (NaLS)/water/cyclohexane/1-pentanol) system. Two orders of magnitude higher life time (20 μs) of the e_aq⁻ has been obtained as compared to that in reverse micelles reported earlier. Several probes including a biomolecule have been used to determine the water pool concentrations and quenching constants (k_q). The observed yield and half life (t_1/2) of the hydrated electrons vary smoothly as the water droplet sizes are changed. The bimolecular rate constants for the reaction of e_aq⁻ with different solutes have been determined. It has been observed that the measured bimolecular rate constants for the reaction of hydrated electrons with different solutes are indicative of the solubilization sites, the water core sizes, and the surrounding environment. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 699–705, 1998     

Realizing both High Energy and High Power Densities by Twisting Three Carbon‐Nanotube‐Based Hybrid Fibers

Energy storage devices, such as lithium‐ion batteries and supercapacitors, are required for the modern electronics. However, the intrinsic characteristics of low power densities in batteries and low energy densities in supercapacitors have limited their applications. How to simultaneously realize high energy and power densities in one device remains a challenge. Herein a fiber‐shaped hybrid energy‐storage device (FESD) formed by twisting three carbon nanotube hybrid fibers demonstrates both high energy and power densities. For the FESD, the energy density (50 mWh cm^?3 or 90 Wh kg^?1) many times higher than for other forms of supercapacitors and approximately 3 times that of thin‐film batteries; the power density (1 W cm^?3 or 5970 W kg^?1) is approximately 140 times of thin‐film lithium‐ion battery. The FESD is flexible, weaveable and wearable, which offers promising advantages in the modern electronics.     

Neutron and beta/gamma radiolysis of water up to supercritical conditions. 1. beta/gamma yields for H(2), H(.) atom, and hydrated electron

Yields for H2, H(.) atom, and hydrated electron production in beta/gamma radiolysis of water have been measured from room temperature up to 400 degrees C on a 250 bar isobar, and also as a function of pressure (density) at 380 and 400 degrees C. Radiolysis was carried out using a beam of 2-3 MeV electrons from a van de Graaff accelerator, and detection was by mass spectrometer analysis of gases sparged from the irradiated water. N2O was used as a specific scavenger for hydrated electrons giving N2 as product. Ethanol-d(6) was used to scavenge H(.) atoms, giving HD as a stable product. It is found that the hydrated electron yield decreases and the H(.) atom yield increases dramatically at lower densities in supercritical water, and the overall escape yield increases. The yield of molecular H2 increases with temperature and does not tend toward zero at low density, indicating that it is formed promptly rather than in spur recombination. A minimum in both the radical and H2 yields is observed around 0.4 kg/dm(3) density in supercritical water.     

Use of CF3,Br/Al,discharges for reactive ion etching of III-V semiconductors

The reactive ion etching of GaAs, InP, InGaAs, and InAlAs in CF₃Br/Ar discharges was investigated as a function of both plasma power density (0.56-1.3 W - cm^–2) and total pressure (10-40 mTorr) The etch rate of GaAs in 19CF₃Br:1Ar discharges at 10 m Torr increases linearly with power density, from 600 Å min^–1 at 0.56 W · cm^–2, to 1550 Å · min at 1.3 W · cm^–2. The in-based materials show linear increases in etch rates only for power densities above – 1.0 W · cm^–2. These etch rates are comparable to those obtained with CCI₂F₂:O₂ mixtures under the same conditions. Smooth surface morphologies and vertical sidewalls are obtained over a wide range of plasma parameters. Reductions in the near-surface carrier concentration in n-type GaAs are evident for etching with power densities of >0.8 W cm^–2, due to the introduction of deep level trapping centers. At 1.3 W· cm^–2, the Schottky barrier height of TiPtAu contacts on GaAs is reduced from 0.74 to 0.53 eV as a result of this damage, and the photoluminescent intensity from the material is degraded. Alter RIE, we detect the presence of both F and Br on the surface of all of the semiconductors. This contamination is worse than with CCl₂F₂-based mixtures. High-power etching with CF₃Br/Ar together with Al-containing electrodes can lead to the presence of a substantial layer of aluminum oxide on the samples if the moisture content in the reactor is appreciable.     

On the nature of solubilized water clusters in aerosol OT/alkane solutions. A study of the formation of hydrated electrons and 1,8-anilinonaphthalene sulphonate fluorescence

The pulse radiolysis of dioctyl sulphosuccinate (aerosol-OT) H₂O/heptane solutions leads to formation of hydrated electrons in the aqueous core of the inverted aerosol-OT micelles. The hydrated electrons are produced via direct interaction of the radiation with the aqueous regions and scavenging of electrons formed initially in the hydrocarbon phase by the water bubbles. The scavenging efficiency decreases with decreasing radius of the water cluster. Hydrated electrons are not formed below a critical size of the solubilized water particles.The quantum yield and wavelength of the maximum of the aniline-naphthalene sulphonate (ANS) fluorescence are strongly dependent on the water content of aerosol-OT inverted micelles. The fluorescence behavior indicates an increase of polarity with increasing cluster radius. The polarity of very large water clusters (r ≈ 73 Å) is still lower than that of bulk water. Water which is bound to Na⁺ counterions cannot effectively participate in the solvation of the dipolar ANS excited states.     

Potassium halide adducts as reagent ions in infrared laser desorption/ionization fourier transform ion cyclotron resonance mass spectrometry

Potassium halide adducts of the form K₂X⁺ (X = F, CI, Br, and I) desorbed from neutral salts by high power, pulsed, infrared laser radiation are detected in abundance by Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry. FT-ICR detection of the K₂X⁺ adduct is favored at increased laser power densities (> 10⁸ W/cm²) and at trapping potentials below 3 V, independent of X. In contrast, detection of K⁺ is promoted at laser power densities below 10⁸ W/cm² or at higher trapping potentials, with a threshold for trapping that is strongly dependent on X. When laser desorption/ionization (LDI)/FT-ICR is performed on 1:1 mixtures of KX and organic molecules, ejection pulses applied continuously at the cyclotron resonance frequency of K₂X⁺ inhibit formation of the cation-attached product, [M + K]⁺. Conversely, resonance ejection of K⁺ enhances [M + K]⁺, apparently by reducing the matrix ion population trapped in the cell. In evaluating higher molecular weight adducts, only K₃F ₂ ⁺ formed in abundance by laser desorption of KF is found through double resonance experiments to contribute significantly to formation of [M + K]⁺. Finally, among the potassium halides, KI generates the highest ratio of detected K₂X⁺ to K⁺ at low trapping potentials and is therefore best suited for cation-transfer reactions in infrared LDI/FT-ICR experiments performed at power densities in the 10⁸ W/cm² range.     

Ultrafast dynamics for electron photodetachment from aqueous hydroxide

Charge-transfer-to-solvent reactions of hydroxide induced by 200 nm monophotonic or 337 and 389 nm biphotonic excitation of this anion in aqueous solution have been studied by means of pump-probe ultrafast laser spectroscopy. Transient absorption kinetics of the hydrated electron, e(aq) (-), have been observed, from a few hundred femtoseconds out to 600 ps, and studied as function of hydroxide concentration and temperature. The geminate decay kinetics are bimodal, with a fast exponential component ( approximately 13 ps) and a slower power "tail" due to the diffusional escape of the electrons. For the biphotonic excitation, the extrapolated fraction of escaped electrons is 1.8 times higher than for the monophotonic 200 nm excitation (31% versus 17.5% at 25 degrees C, respectively), due to the broadening of the electron distribution. The biphotonic electron detachment is very inefficient; the corresponding absorption coefficient at 400 nm is <4 cm TW(-1) M(-1) (assuming unity quantum efficiency for the photodetachment). For [OH(-)] between 10 mM and 10 M, almost no concentration dependence of the time profiles of solvated electron kinetics was observed. At higher temperature, the escape fraction of the electrons increases with a slope of 3x10(-3) K(-1) and the recombination and diffusion-controlled dissociation of the close pairs become faster. Activation energies of 8.3 and 22.3 kJ/mol for these two processes were obtained. The semianalytical theory of Shushin for diffusion controlled reactions in the central force field was used to model the geminate dynamics. The implications of these results for photoionization of water are discussed.     

Computational study of carbon monooxide absorption by ultradisperse systems. Emission spectra

Molecular dynamics was used to study absorption of carbon monoxide molecules by water clusters combined into two groups (2–10 and 11–20 water molecules) on the basis of their statistical weights. Spectral characteristics of the clusters in the frequency range 0 ≤ ω ≤ 1000 cm^?1 were established. Within this range, the integral IR adsorption intensity of both systems increases with addition of CO molecules. The IR emission power increases significantly after a cluster has absorbed one CO molecule but decreases with the absorption of a further CO molecule. A similar situation is observed with the number of electrons “active” toward external electromagnetic radiation. As the smallest clusters containing two CO molecules grow by adding water molecules, the IR emission power decreases. In other cases, these changes are of a periodical character.     

Preparation,Characterization and Permeation Study of Topical Gel Loaded with Transfersomes Containing Asiatic Acid

The objective of this study is to investigate the in vitro permeation of asiatic acid (AA) in the form of a topical gel after entrapment in transfersomes by Franz diffusion cells. Transfersomes composed of soybean lecithin and three different edge activators including Tween 80 (TW80), Span 80 (SP80) and sodium deoxycholate (SDC) at the ratio of 50:50, 90:10 and 90:10, respectively, together with 0.3% w/w of AA, were prepared by a high-pressure homogenization technique and further incorporated in gels (TW80AATG, SP80AATG and SDCAATG). All transfersomal gels were characterized for their AA contents, dynamic viscosity, pH and homogeneity. Results revealed that the AA content, dynamic viscosity and pH of the prepared transfersomal gels ranged from 0.272 ± 0.006 to 0.280 ± 0.005% w/w, 812.21 ± 20.22 to 1222.76 ± 131.99 Pa.s and 5.94 ± 0.03 to 7.53 ± 0.03, respectively. TW80AATG gave the highest percentage of AA penetration and flux into the Strat-M^® membrane at 8 h (8.53 ± 1.42% and 0.024 ± 0.008 mg/cm²/h, respectively) compared to SP80AATG (8.00 ± 1.70% and 0.019 ± 0.010 mg/cm²/h, respectively), SDCAATG (4.80 ± 0.50% and 0.014 ± 0.004 mg/cm²/h, respectively), non-transfersomal gels (0.73 ± 0.44 to 3.13 ± 0.46% and 0.002 ± 0.001 to 0.010 ± 0.002 mg/cm²/h, respectively) and hydroethanolic AA solution in gel (1.18 ± 0.76% and 0.004 ± 0.003 mg/cm²/h, respectively). These findings indicate that the TW80AATG might serve as a lead formulation for further development toward scar prevention and many types of skin disorders.     

Infrared and near-infrared spectroscopic study of synthetic hydrotalcites with variable divalent/trivalent cationic ratios

Near-infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to hydrotalcites of the formula Mg₆ (Fe,Al)₂(OH)₁₆(CO₃)·4H₂O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio. Such hydrotalcites were found to show variation in the d-spacing attributed to the size of the cation. In the IR (1750–4000 cm⁻¹), the position of all bands except those at approximately 3060 cm⁻¹ shift to higher wavenumbers as the cation ratio increases. Conversely, at wavenumbers below 1000 cm⁻¹, the bands shift to lower wavenumbers as the cation ratio increases. A water bending mode at higher wavenumbers was also observed which indicates that the water is strongly hydrogen bonded. In the NIR spectrum between 8000 and 12,000 cm⁻¹, there is a broad feature which is attributed to electronic bands of the ferrous ion and low intensity sharp bands due to overtones of the OH stretching vibrations. It is also apparent from this region that Fe²⁺ substitutes for Mg²⁺. The intensity of bands at 7750 and 5200 cm⁻¹ increases as the cation ratio increases in the NIR spectrum. Hydrotalcites with a magnesium amount 3 and 4 times greater than that of aluminium and iron combined, in the lower wavenumber region of the NIR spectrum, have very similar spectral profiles. This work has shown that hydrotalcites with different divalent/trivalent ratios can be synthesised and characterised by infrared spectroscopy.     

Hydrated Eutectic Electrolytes Stabilizing Quasi-Underpotential Mg Plating/Stripping for High-Voltage Mg Batteries

Aqueous rechargeable Mg batteries (ARMBs) usually fail from severe anode passivation, alternatively, executing quasi-underpotential Mg plating/stripping chemistry (UPMC) on a proper heterogeneous metal substrate is a crucial remedy. Herein, a stable UPMC on Zn substrate is initially achieved in new hydrated eutectic electrolytes (HEEs), delivering an ultralow UPMC overpotential and high energy/voltage plateau of ARMBs. The unique eutectic property remarkably expands the lower limit of electrochemical stability window (ESW) of HEEs and undermines the competition between hydrogen evolution/corrosion reactions and UPMC, enabling a reversible UPMC. The UPMC is carefully revealed by multiple characterizations, which shows a low overpotential of 50 mV at 0.1 mA cm⁻² over 550 h. With sulfonic acid-doped polyaniline (SPANI) cathodes, UPMC-based full cells show high energy/power densities of 168.6 Wh kg⁻¹/2.1 kWh kg⁻¹ and voltage plateau of 1.3 V, far overwhelming conventional aqueous systems.     

NaYF4:Yb,Er/NaYF4 Core/Shell Nanocrystals with High Upconversion Luminescence Quantum Yield

Upconversion core/shell nanocrystals with different mean sizes ranging from 15 to 45 nm were prepared via a modified synthesis procedure based on anhydrous rare‐earth acetates. All particles consist of a core of NaYF₄:Yb,Er, doped with 18 % Yb³⁺ and 2 % Er³⁺, and an inert shell of NaYF₄, with the shell thickness being equal to the radius of the core particle. Absolute measurements of the photoluminescence quantum yield at a series of different excitation power densities show that the quantum yield of 45 nm core/shell particles is already very close to the quantum yield of microcrystalline upconversion phosphor powder. Smaller core/shell particles prepared by the same method show only a moderate decrease in quantum yield. The quantum yield of 15 nm core/shell particles, for instance, is reduced by a factor of three compared to the bulk upconversion phosphor at high power densities (100 W cm^?2) and by approximately a factor of 10 at low power densities (1 W cm^?2).     

Hydrogen Peroxide Solvates of 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane

Two polymorphic hydrogen peroxide solvates of 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20; wurtzitane is an alternative name to iceane) were obtained using hydrated α‐CL‐20 as a guide. These novel H₂O₂ solvates have high crystallographic densities (1.96 and 2.03 g cm^?3, respectively), high predicted detonation velocities/pressures (with one solvate performing better than ?‐CL‐20), and a sensitivity similar to that of ?‐CL‐20. The use of hydrated materials as a guide will be important in the development of other energetic materials with hydrogen peroxide. These solvates represent an area of energetic materials that has yet to be explored.     

Adsorption of ammonia by water clusters. Computer experiment

The method of molecular dynamics is used to study the adsorption of from one to six ammonia molecules by water clusters composed of 50 molecules. The adsorption of NH₃ molecules markedly increases the IR absorption spectrum intensity, substantially decreases emission power in the frequency range of 0 ≤ ω ≤ 3500 cm^?1, and transforms a continuous reflectance spectrum into a banded one. A rough surface formed by adsorbed ammonia molecules reduces the absorption coefficient and refractive index of the system of water-ammonia clusters in the entire frequency range. Adsorption of ammonia molecules by water clusters greatly diminishes the number of electrons that are active with respect to electromagnetic radiation.     

Scaling up Studies on PEMFC Using a Modified Serpentine Flow Field Incorporating Porous Sponge Inserts to Observe Water Molecules

Flooding of the cathode flow channel is a major hindrance in achieving maximum performance from Proton Exchange Membrane Fuel Cells (PEMFC) during the scaling up process. Water accumulated between the interface region of Gas Diffusion Layer (GDL) and rib of the cathode flow field can be removed by the use of Porous Sponge Inserts (PSI) on the ribs. In the present work, the experimental investigations are carried out on PEMFC for the various reaction areas, namely 25, 50 and 100 cm². Stoichiometry value of 2 is maintained for all experiments to avoid variations in power density obtained due to differences in fuel utilization. The experiments include two flow fields, namely Serpentine Flow Field (SFF) and Modified Serpentine with Staggered provisions of 4 mm PSI (4 mm × 2 mm × 2 mm) Flow Field (MSSFF). The peak power densities obtained on MSSFF are 0.420 W/cm², 0.298 W/cm² and 0.232 W/cm² compared to SFF which yields 0.242 W/cm², 0.213 W/cm² and 0.171 W/cm² for reaction areas of 25, 50 and 100 cm² respectively. Further, the reliability of experimental results is verified for SFF and MSSFF on 25 cm² PEMFC by using Electrochemical Impedance Spectroscopy (EIS). The use of 4 mm PSI is found to improve the performance of PEMFC through the better water management.     

Cyclometalated ruthenium complex as a promising sensitizer in dye-sensitized solar cells

Ruthenocycle bis(4,4′-dicarboxy-2,2′-bipyridine)(2-phenylpyridine-²C,N)ruthenium(II) hexafluorophosphate was used as a sensitizer in a dye-sensitized solar cell (DSSC) based on nanocrystalline TiO₂, which was applied onto a conducting substrate. Its electrochemical and spectral characteristics were studied. It was found that, when the DSSC was illuminated with visible light of power 35 mW/cm², the short-circuit current density was 11.6 mA cm^?2 and the open-circuit voltage was 0.49 V. The efficiency (η) of DSSC at a fill factor of 45% was 7.1%. Using the method of modulation spectroscopy of photocurrents and photopotentials, the life time and transit time of electrons were found to be 7 and 5 ms, respectively, and the diffusion coefficient of electrons was found to be 10^?5 cm² s^?1. Comparing the life and transit times of electron, it was concluded that the photogenerated electrons had time to reach the conducting substrate during their life time.     

Single SOFC with Supporting Ni-YSZ Anode,Bilayer YSZ/GDC Film Electrolyte,and La<Subscript>2</Subscript>NiO<Subscript>4 + δ</Subscript> Cathode

Characteristics of fuel cells with supporting Ni-YSZ anode, bilayer YSZ/GDC electrolyte with the thickness of 10 μm, and La₂NiO_{4 + δ} cathode are studied. It is shown that when humid (3% water) hydrogen is supplied to the anode and air is supplied to the cathode, the maximum values of cell’s power density are 1.05 and 0.75 W/cm² at 900 and 800°С, respectively. After the introduction of praseodymium oxide and ceria into the cathode and the anode, respectively, the power density is ca. 1 W/cm² at 700°С. It is found that the power density of a cell with impregnated electrodes weakly increases with the increase in temperature to ca. 1.4 W/cm² at 900°С. The analysis of impedance spectra by the distribution of relaxation times shows that such behavior is associated with the gas-diffusion resistance of the SOFC anode. The latter is explained by the low porosity of the anode and the high rate of fuel consumption.     

Fabric‐based alkaline direct formate microfluidic fuel cells

Fabric‐based microfluidic fuel cells (MFCs) serve as a novel, cost‐efficient alternative to traditional FCs and batteries, since fluids naturally travel across fabric via capillary action, eliminating the need for an external pump and lowering production and operation costs. Building on previous research with Y‐shaped paper‐based MFCs, fabric‐based MFCs mitigate fragility and durability issues caused by long periods of fuel immersion. In this study, we describe a microfluidic fabric‐based direct formate fuel cell, with 5 M potassium formate and 30% hydrogen peroxide as the anode fuel and cathode oxidant, respectively. Using a two‐strip, stacked design, the optimized parameters include the type of encasement, the barrier, and the fabric type. Surface contact of the fabric and laminate sheet expedited flow and respective chemical reactions. The maximum current (22.83 mA/cm²) and power (4.40 mW/cm²) densities achieved with a 65% cotton/35% polyester blend material are a respective 8.7% and 32% higher than previous studies with Y‐shaped paper‐based MFCs. In series configuration, the MFCs generate sufficient energy to power a handheld calculator, a thermometer, and a spectrum of light‐emitting diodes.     

Breaking the nanosecond barrier in FTIR time-resolved spectroscopy

The state of the art in broad spectral bandwidth infrared time-resolved spectroscopy (IRTRS) is reviewed, with particular regard to time resolution in the nanosecond and sub-nanosecond regime. While step-scan Fourier transform infrared (S²FTIR) has been successful in pushing the time resolution of IRTRS to sub-microsecond limits, and is, in principle, applicable for monitoring time-dependent phenomena on any time scale, a practical limit for S²FTIR is currently about 1 ns, due to the limitations of parts of the instrument other than the interferometer itself. For the particular case of IRTRS of transient photo-excited states illustrated here and other photo-excitation studies, it is proposed that the most effective way to breach the nanosecond barrier and to push the time resolution limit of IRTRS to 10 ps, or even lower, while still maintaining the spectral bandwidth and resolution and the multiplex and throughput advantages of interferometry, is to turn to constant velocity, continuous-scan (CS) FTIR, in the pump–probe asynchronous sampling mode. In the method described, the pump is provided by the picosecond UV pulse of an electron storage ring-powered free electron laser and the infrared probe is the picosecond `white light' synchrotron pulse from the same storage ring. The design specifications of this system are 10 ps time resolution with 3 cm⁻¹ spectral resolution.