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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Pronounced Dielectric and Hydration/Dehydration Behaviors of Monopolar Poly( N -alkylglycine)s in Aqueous Solution

Poly(N-methylglycine) (NMG n ) and poly(N-ethylglycine) (NEG n ) obtained by polymerization reactions initiated by benzylamine have no carboxy termini, such as those in normal polyamides, but have only amino termini, which exist primarily as cations in aqueous media at a pH value of ca. 9.5, observed in aqueous solutions without any buffer reagents. Therefore, polypeptoids, such as NMG n and NEG n , possessing a degree of polymerization (DP) higher than a certain value behave as cationic monopolar polymeric chain molecules in aqueous solution. It has not been clarified so far whether such a monopolar chain molecule exhibits dielectric relaxation (DR) behavior resulting from its molecular motions in aqueous media as dipolar chain molecules. DR measurements revealed that NMG 19 and NEG 17 , possessing DPs of 19 and 17, respectively, dissolved in pure water clearly demonstrated pronounced DR behavior caused by fluctuating molecular motions of cationic termini at relaxation times of ca. 4 and 9 ns at 10 °C (283 K). The hydration numbers of NMG 19 and NEG 17 per monomeric residue (nm) in aqueous solution were also evaluated via DR data as functions of temperature, and the nm value of ca. 4.5 at 10 °C showed a remarkable reduction to ca. 2.0 around 40 °C (313 K) and 30 °C (303 K), depending on differences in the substituted group: methyl and ethyl groups. Furthermore, this temperature-dependent hydration/dehydration behavior found in NMG 19 and NEG 17 slightly influenced the sizes and molecular dynamics of the monopolar chain molecules in aqueous solution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Stable Aqueous Dispersions of Hydrophobically Modified Titanium Dioxide Pigments through Polyanion Adsorption: Synthesis, Characterization, and Application in Coatings

Polyanion dispersants stabilize aqueous dispersions of hydrophilic (native) inorganic oxide particles, including pigments currently used in paints, which are used at an annual scale of 3 million metric tons. While obtaining stable aqueous dispersions of hydrophobically modified particles has been desired for the promise of improved film performance and water barrier properties, it has until now required either prohibitively complex polyanions, which represent a departure from conventional dispersants, or multistep syntheses based on hybrid-material constructs. Here, we demonstrate the aqueous dispersion of alkylsilane-capped inorganic oxide pigments with conventional polycarboxylate dispersants, such as carboxymethylcellulose (CMC) and polyacrylate, as well as a commercial anionic copolymer. Contact-angle measurements demonstrate that the hydrophobically modified pigments retain significant hydrophobic character even after adsorbing polyanion dispersants. CMC adsorption isotherms demonstrate 92% greater polyanion loading on trimethylsilyl modified hydrophobic particles relative to native oxide at pH 8. However, consistent with prior literature, hydrophobically modified silica particles adsorb polyanions very weakly under these conditions. These data suggest that Lewis acidic heteroatoms such as Al 3+ sites on the pigment surface are necessary for polyanion adsorption. The adsorbed polyanions increase the dispersion stability and zeta potential of the particles. Based on particle sedimentation under centrifugal force, the hydrophobically modified pigments possess greater dispersion stability with polyanions than the corresponding native hydroxylated particles. The polyanions also assist in the aqueous wetting of the hydrophobic particles, facilitating the transition from a dry powder into an aqueous dispersion of primary particles using less agitation than the native hydroxylated pigment. The application of aqueous dispersions of hydrophobically modified oxide particles to waterborne coatings leads to films that display lower water uptake at high relative humidities and greater hydrophilic stain resistances. Finally, this improved film performance with hydrophobically modified pigments is the result of better association between latex polymer and pigment in the dry film.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stabilizing Aqueous Three-Dimensional Printed Constructs Using Chitosan-Cellulose Nanocrystal Assemblies

The assembly and binding of nanoparticles at the interfaces of aqueous two-phase systems enable the three-dimensional (3D) printing of all-aqueous naturally occurring materials. When a dispersion of cellulose nanocrystals (CNCs) in an aqueous solution of polyethylene glycol (PEG) is brought into contact with chitosan dissolved in an aqueous solution of dextran, the CNCs and chitosan diffuse to the interface between the two immiscible aqueous solutions, electrostatically interact, and form a solid, membranous layer sufficiently rapidly to 3D print tubules of one liquid in the other. Additionally, the diameter, length, spatial arrangement, and stability of the printed tubules can be broadly controlled. Adsorption and directional diffusion of ionic species across the membranous layer make heavy metal ion removal possible. The results present a platform for fabricating and developing all-aqueous compartmentalized systems where function can be independently coupled to the inherent functionality of the nanoparticles or ligands.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Polyanionic insertion hosts for aqueous rechargeable batteries

Safety concerns and costs of present-day lithium-ion batteries (LIBs) are prompting the development of alternate battery technologies with different types of electrolyte ( e.g. , solid-state, gel-polymer, aqueous, etc. ); notably, systems based on aqueous electrolytes have emerged as a promising alternative, especially for grid storage applications. The last decade has witnessed a considerable spike in the research carried out on aqueous batteries. However, the narrow operating voltage window of aqueous electrolytes and the structural instability of materials in aqueous media demand proper selection of cathode materials to achieve desirable energy density. Polyanionic materials can be an ideal choice as they are structurally more stable and exhibit tunable redox potentials. This class of materials is considered as a storehouse in which many materials can be realized by substituting different polyanionic subunits. Here, this review highlights some of the recent advances made in the polyanionic class of cathode materials for rechargeable aqueous batteries (Li-, Na- and Zn-ion batteries). The challenges facing the field, possible remedies to overcome them and future perspectives are also presented.

25 ENERGY STORAGE↗
DOE OSTI2025

Spectroscopic investigation of cation effects in U(VI)-NO3- complexation in aqueous solutions

Understanding and manipulating uranyl speciation in aqueous solutions is critical for advancing chemical separation, sensing, and understanding environmental transport of uranyl. We report on the significant enhancement in the complexation of uranyl with nitrate in aqueous solutions containing quaternary ammonium cations leading to the formation of anionic complexes. We base this on the comparative study of the effect of monovalent cations (Na+, Li+, NH4+, and N(CH3)4+) on the complexation equilibria of uranyl-nitrate in solutions, probed by time-resolved laser induced fluorescence spectroscopy (TRLFS). Lifetime-corrected spectra, obtained by extrapolating the time-resolved spectra to t = 0, were used to study speciation to mitigate the effects of variations in the fluorescence lifetimes that depend on extraneous factors such as dynamic quenching. We demonstrate that the lifetime-corrected spectra can be used to determine uranyl speciation in aqueous solutions where the mono-nitrate complex forms, and in acetonitrile with N(CH3)4NO3 where di-nitrate and tris-nitrato species are formed. Aqueous solutions containing N(CH3)4+ are shown to promote the formation of higher complexes of uranyl compared to other inorganic nitrate salts based on the higher redshift in the spectra, poor fits to the two-component model, and the higher apparent formation constants. Comparing the trends in uranyl speciation in the presence of N(CH3)4+ in aqueous and acetonitrile solutions, it is proposed that the quaternary ammonium cations (quats) promote the formation of anionic complexes of uranyl by the ion-association mechanism. These results provide a basis for designing quat-assisted separation systems that target anionic actinide species in aqueous solutions.

Nayak, Srikanth (ORCID:0000000302135796)↗
DOE OSTI2011

Atomistic insights into aqueous corrosion of copper.

Corrosion is a fundamental problem in electrochemistry and represents a mode of failure of technologically important materials. Understanding the basic mechanism of aqueous corrosion of metals such as Cu in presence of halide ions is hence essential. Using molecular dynamics simulations incorporating reactive force-field (ReaxFF), the interaction of copper substrates and chlorine under aqueous conditions has been investigated. These simulations incorporate effects of proton transfer in the aqueous media and are suitable for modeling the bond formation and bond breakage phenomenon that is associated with complex aqueous corrosion phenomena. Systematic investigation of the corrosion process has been carried out by simulating different chlorine concentration and solution states. The structural and morphological differences associated with metal dissolution in the presence of chloride ions are evaluated using dynamical correlation functions. The simulated atomic trajectories are used to analyze the charged states, molecular structure and ion density distribution which are utilized to understand the atomic scale mechanism of corrosion of copper substrates under aqueous conditions. Increased concentration of chlorine and higher ambient temperature were found to expedite the corrosion of copper. In order to study the effect of solution states on the corrosion resistance of Cu, partial fractions of proton or hydroxide in water were configured, and higher corrosion rate at partial fraction hydroxide environment was observed. When the Cl{sup -} concentration is low, oxygen or hydroxide ion adsorption onto Cu surface has been confirmed in partial fraction hydroxide environment. Our study provides new atomic scale insights into the early stages of aqueous corrosion of metals such as copper.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Trivalent Lanthanide/Actinide Separation Using Aqueous-Modified TALSPEAK Chemistry

TALSPEAK is a liquid/liquid extraction process designed to separate trivalent lanthanides (Ln3+) from minor actinides (MAs) Am3+ and Cm3+. Traditional TALSPEAK organic phase is comprised of a monoacidic dialkyl bis(2-ethylhexyl)phosphoric acid extractant (HDEHP) in diisopropyl benzene (DIPB). The aqueous phase contains a soluble aminopolycarboxylate diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (DTPA) in a concentrated (1.0-2.0 M) lactic acid (HL) buffer with the aqueous acidity typically adjusted to pH 3.0. TALSPEAK balances the selective complexation of the actinides by DTPA against the electrostatic attraction of the lanthanides by the HDEHP extractant to achieve the desired trivalent lanthanide/actinide group separation. Although TALSPEAK is considered a successful separations scheme, recent fundamental studies have highlighted complex chemical interactions occurring in the aqueous and organic phases during the extraction process. Previous attempts to model the system have shown thermodynamic models do not accurately predict the observed extraction trends in the p[H+] range 2.5-4.8. In this study, the aqueous phase is modified by replacing the lactic acid buffer with a variety of simple and longer-chain amino acid buffers. The results show successful trivalent lanthanide/actinide group separation with the aqueous-modified TALSPEAK process at pH 2. The amino acid buffer concentrations were reduced to 0.5 M (at pH 2) and separations were performed without any effect on phase transfer kinetics. Successful modeling of the aqueous-modified TALSPEAK process (p[H+] 1.6-3.1) using a simplified thermodynamic model and an internally consistent set of thermodynamic data is presented.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1992

ASRM Process Development in Aqueous Cleaning

Viewgraphs are included on process development in aqueous cleaning which is taking place at the Aerojet Advanced Solid Rocket Motor (ASRM) Division under a NASA Marshall Space and Flight Center contract for design, development, test, and evaluation of the ASRM including new production facilities. The ASRM will utilize aqueous cleaning in several manufacturing process steps to clean case segments, nozzle metal components, and igniter closures. ASRM manufacturing process development is underway, including agent selection, agent characterization, subscale process optimization, bonding verification, and scale-up validation. Process parameters are currently being tested for optimization utilizing a Taguci Matrix, including agent concentration, cleaning solution temperature, agitation and immersion time, rinse water amount and temperature, and use/non-use of drying air. Based on results of process development testing to date, several observations are offered: aqueous cleaning appears effective for steels and SermeTel-coated metals in ASRM processing; aqueous cleaning agents may stain and/or attack bare aluminum metals to various extents; aqueous cleaning appears unsuitable for thermal sprayed aluminum-coated steel; aqueous cleaning appears to adequately remove a wide range of contaminants from flat metal surfaces, but supplementary assistance may be needed to remove clumps of tenacious contaminants embedded in holes, etc.; and hot rinse water appears to be beneficial to aid in drying of bare steel and retarding oxidation rate.

Swisher, Bill↗
NASA NTRS1999

Aqueous Cleaning and Validation for Space Shuttle Propulsion Hardware at the White Sands Test Facility

The NASA White Sands Test Facility (WSTF) has developed an entirely aqueous final cleaning and verification process to replace the current chlorofluorocarbon (CFC) 113 based process. This process has been accepted for final cleaning and cleanliness verification of WSTF ground support equipment. The aqueous process relies on ultrapure water at 50 C (323 K) and ultrasonic agitation for removal of organic compounds and particulate. The cleanliness is verified bv determining the total organic carbon (TOC) content and filtration with particulate counting. The effectiveness of the aqueous methods for detecting hydrocarbon contamination and particulate was compared to the accepted CFC 113 sampling procedures. Testing with known contaminants, such as hydraulic fluid and cutting and lubricating oils, to establish a correlation between aqueous TOC and CFC 113 nonvolatile residue (NVR) was performed. Particulate sampling on cleaned batches of hardware that were randomly separated and sampled by the two methods was performed. This paper presents the approach and results, and discusses the issues in establishing the equivalence of aqueous sampling to CFC 113 sampling, while describing the approach for implementing aqueous techniques on Space Shuttle Propulsion hardware.

Hornung, Steven D.↗
NASA NTRS2004

Geochemical and Mineralogical Indicators for Aqueous Processes in Gusev Crater and on Meridiani Planum

The Athena Science Instrument Payload is providing geochemical and mineralogical information for determining the properties of rocks, soils, and outcrops at the Mars Exploration Rovers landing sites. These measurements indicate that a variety of aqueous processes as well as various degrees of alteration occurred at the two landing sites. Light-toned rocks around the Spirit landing site appear to have coatings or alteration rinds that may have resulted from limited aqueous alteration on the surfaces of basaltic rocks. Hematite and high Fe(III)lFe(total) occur at the surfaces of these rocks. High concentrations of elements highly mobile in water (i.e., S, Cl, and Br) occur in rock veins, vugs, and coatings and at the bottom of soil trenches in the "intercrater plains." One scenario for the formation of rock coatings or rinds and translocation of mobile elements is that water might have occurred briefly at the Martian surface during periods of high obliquity and thin films of water may have mobilized elements and altered the surfaces of rocks. Outcrops on the slopes of the Columbia Hills appear to be extensively altered as suggested by their relative "softness" (measured as resistance to abrasion) as compared to basalts on the adjacent plains, high Fe(III)lFe(total), iron mineralogy dominated by nanophase Fe(III) oxides and hematite, and high Br and CI concentrations beneath outcrop surfaces. These outcrops may have formed by the alteration of basaltic rocks and/or volcaniclastic materials by solutions that were rich in volatile elements (e.g., Br, CI, S). However, it is not clear whether aqueous alteration occurred at depth (e.g., metasomatism), by hydrothermal solutions (e.g., associated with volcanic or impact processes), by vapors rich in volcanic gases, or by low-temperature solutions. The occurrence of jarosite, hematite, and other sulfates (e.g., Mg sulfates) in Eagle and Endurance crater outcrops are strong indicators of aqueous processes at Meridiani Planum. These phases occur with siliciclastic materials in outcrops. Jarosite can only form by aqueous processes under very acidic conditions; e.g., acid sulfate weathering conditions resulting from the oxidation of Fe sulfides or by sulfuric acid alteration of basalts by solutions associated with S02-rich volcanic gases. It is plausible that acidic solutions rich in sulfur (and Fe(II)) reacted with basaltic sediments (which provided a host of soluble cations) under oxidizing conditions and then, through evaporation, formed sediments rich in jarosite and other sulfates along with siliciclastic materials. Hematite-rich spherules in outcrops may have formed by aqueous processes within the sedimentary layers, which promoted transport of Fe (II) solutions to nucleation sites where oxidation and precipitation occurred to form hematite-rich spherules.

Ming, Douglas W.↗
DOE OSTI2021

Lipophilic guanidinium compounds for removal of oxyanions from aqueous solutions

Methods for removing an oxyanion from an aqueous source containing said oxyanion, comprising contacting said aqueous source with an aqueous-insoluble hydrophobic solution containing an oxyanion extractant compound dissolved in an aqueous-insoluble hydrophobic solvent to result in formation of an oxyanion salt of said extractant compound and extraction of said oxyanion salt into said aqueous-insoluble hydrophobic solution, wherein said extraction results in an extraction affinity (D) of said oxyanion of at least 1, wherein D is the concentration ratio of said oxyanion in the organic phase divided by the concentration of said oxyanion in the aqueous phase; wherein said extractant compound has the following composition: wherein at least one of R1-R10 is or contains a hydrocarbon (R) group containing at least 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms.

Williams, Neil John↗
DOE OSTI2021

Enabling aqueous processing for LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA)-based lithium-ion battery cathodes using polyacrylic acid

Replacing N-methyl-2-pyrrolidone (NMP) with water in the production of lithium-ion battery cathodes is critical to realizing process cost savings and improved worker safety. LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) is a poor fit for aqueous processing due to destructive Al current collector corrosion resulting from highly basic slurries and detrimental surface reconstruction reactions that occur in water. In this study, polyacrylic acid (PAA, MW = 450,000 g·mol -1 ) is examined as a corrosion-mitigating and surface-stabilizing agent. Adding PAA to an aqueous NCA slurry can provide a stable pH (4.0–8.5) for at least 4 h, since the carboxyl groups from PAA dissociate and increase the proton concentration in the slurry. Further, these groups can also adsorb to the surface of NCA particles and provide electrostatic stability from active material particle agglomeration, as revealed by zeta potential measurements. Minor cracking does occur at the electrode surface; this cracking likely caused poorer adhesion to the Al current collector in the aqueous-processed film when compared to the NMP-processed baseline. Electrochemically, the leached Li does cause a lower initial capacity for the aqueous-processed cathode, though the capacity retention of the aqueous-processed cathode is better than the baseline. The cracks in the coating led to a rise in charge transfer resistance that hindered rate capability above 1C.

25 ENERGY STORAGE↗
DOE OSTI2018

Aqueous geochemistry at gigapascal pressures: NMR spectroscopy of fluoroborate solutions

Aqueous geochemistry could be extended considerably if nuclear-magnetic resonance (NMR) methods could be adapted to study solutions at elevated temperatures and pressures. We therefore designed an NMR probe that can be used to study aqueous solutions at gigapascal pressures. Fluoride solutions were chosen for study because 19 F couples to other nuclei in the solutions ( 31 P and 11 B) in ways that make peak assignments unequivocal. Correspondingly, NMR spectra of 19 F- and 11 B were collected on aqueous HBF 4 -NH 4 PF 6 solutions to pressures up to 2.0 GPa. At pressure, peaks in the 19 F spectra were clear and assignable to the BF 4 – (aq), F – (aq) and BF 3 OH – (aq) ions, and these aqueous complexes varied in signal intensity with pressure and time, for each solution. Peaks in the 11 B spectra at pressure could be assigned to the BF 4 – (aq) and BF 3 OH – (aq) species. Additionally, there is a single peak that is assignable to H 3 BO 3 o (aq) and B(OH) 4 – (aq) in rapid-exchange equilibria. These peaks broaden and move with pressure in ways that suggest reversible interconversion of borate and fluoroborate species. The PF 6 – ion was found to provide a suitable 19 F shift and intensity standard for high-pressure spectra because it was chemically inert. Here, the positions and intensities of the doublet peak also remains constant as a function of pressure and pH. Addition of electrolytes considerably distorts the phase diagram of water such that the stability region of the aqueous solution expands to well beyond the 0.8 GPa freezing pressure of pure water; some fluoroborate solutions remain liquid until almost 2.0 GPa.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Aqueous Processed All-Polymer Solar Cells with High Open-Circuit Voltage Based on Low-Cost Thiophene–Quinoxaline Polymers

Eco-friendly solution processing and the low-cost synthesis of photoactive materials are important requirements for the commercialization of organic solar cells (OSCs). Although varieties of aqueous-soluble acceptors have been developed, the availability of aqueous-processable polymer donors remains quite limited. In particular, the generally shallow highest occupied molecular orbital (HOMO) energy levels of existing polymer donors limit further increases in the power conversion efficiency (PCE). Here, we design and synthesize two water/alcohol-processable polymer donors, poly[(thiophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-T)) and poly[(selenophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-Se)) with oligo(ethylene glycol) (OEG) side chains, having deep HOMO energy levels (~–5.4 eV). The synthesis of the polymers is achieved in a few synthetic and purification steps at reduced cost. The theoretical calculations uncover that the dielectric environmental variations are responsible for the observed band gap lowering in OEG-based polymers compared to their alkylated counterparts. Notably, the aqueous-processed all-polymer solar cells (aq-APSCs) based on P(Qx8O-T) and poly[(N,N'-bis(3-(2-(2-(2-methoxyethoxy)-ethoxy)ethoxy)-2-((2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-methyl)propyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-(2,5-thiophene)] (P(NDIDEG-T)) active layer exhibit a PCE of 2.27% and high open-circuit voltage (V OC ) approaching 0.8 V, which are among the highest values for aq-APSCs reported to date. This study provides important clues for the design of low-cost, aqueous-processable polymer donors and the fabrication of aqueous-processable OSCs with high V OC .

14 SOLAR ENERGY↗
DOE OSTI2019

Strategies to Valorize the Hydrothermal Liquefaction-Derived Aqueous Phase into Fuels and Chemicals

Valorization options for the aqueous fraction produced by the hydrothermal liquefaction of terrestrial feedstocks were developed. The processes focused on carboxylic acids, which are abundant in the aqueous fraction. A clean up process for the aqueous phase based on activated carbon absorption followed by liquid-liquid extraction was demonstrated that significantly reduces color bodies and inorganic contaminants while simultaneously concentrating desirable organic constituents. Conversion of the cleaned aqueous phase was then demonstrated for both a ketonization reaction and steam reforming. Condensed phase ketonization over LaxZryOz catalyst was found to exhibit both excellent hydrothermal stability and ketonization activity. Necessity for feedstock cleanup was established and stable condensed phase ketonization operation was demonstrated for ~100 hours with HTL-process derived material. Steam reforming was also demonstrated by employing a dual-bed catalyst configuration whereby carboxylic acids first undergo ketonization over CeO2 in the vapor phase followed by steam reforming of the ketone intermediates over Co/CeO2. The dual-bed approach reduced coke deposition and thus catalyst stability improved. Techno-economic analysis was used to assess economic viability for producing fuel from the bio-oil fraction and either propene (formed via hydrogenation and dehydration of acetone, the primary ketonization product) or hydrogen from the aqueous stream. The ketonization and steam reforming cases were separately modeled and benchmarked to a process utilizing anaerobic digestion. Resulting minimum fuel selling prices of $3.7, $4.2, and $4.3/GGE were obtained for the production of olefins via ketonization, reduction and dehydration; steam reforming; and anaerobic digestion processes, respectively. Both the steam reforming and anaerobic digestion processes benefited by avoiding the need for natural gas by producing the hydrogen on-site required for biocrude hydrotreatment. However, the condensed ketonization process had the lowest minimum fuel selling price because of the co-product olefins generated for sale.

Biomass, hydrothermal liquefaction, techno economi↗
DOE OSTI2014

First-principles Study of Phenol Hydrogenation on Pt and Ni Catalysts in Aqueous Phase

The effects of aqueous phase on the reactivity of phenol hydrogenation over Pt and Ni catalysts were investigated using density functional theory based ab initio molecular dynamics (AIMD) calculations. The adsorption of phenol and the first hydrogenation steps via three carbon positions (ortho, meta and para) with respect to the phenolic OH group were studied in both vacuum and liquid phase conditions. To gain insight into how the aqueous phase affects the metal catalyst surface, increasing water environments including singly adsorbed water molecule, mono- (9 water molecules), double layers (24 water molecules), and the bulk liquid water which (52 water molecules) on the Pt(111) and the Ni(111) surfaces were modeled. Compared to the vacuum/metal interfaces, AIMD simulation results suggest that the aqueous Pt(111) and Ni(111) interfaces have a lower metal work function in the order of 0.8 - 0.9 eV, thus, making the metals in aqueous phase stronger reducing agents and poorer oxidizing agents. Phenol adsorption from the aqueous phase is found to be slightly weaker that from the vapor phase. The first hydrogenation step of phenol at the ortho position of the phenolic ring is slightly favored over the other two positions. The polarization induced by the surrounding water molecules and the solvation effect play important roles in stabilizing the transition states associated with phenol hydrogenation by lowering the barriers of 0.1 - 0.4 eV. The detailed discussion on the basis of the interfacial electrostatics from the current study is very useful to understand the nature of a broader class of metal catalyzed reactions in liquid solution phase. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences and Office of Energy Efficiency and Renewable Energy. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) and by the National Energy Research Scientific Computing Center (NERSC). EMSL is a national scientific user facility located at Pacific Northwest National Laboratory (PNNL) and sponsored by DOE’s Office of Biological and Environmental Research.

aqueous phase↗
DOE OSTI2013

Atmospheric-pressure air microplasma jets in aqueous media for the inactivation of Pseudomonas fluorescens cells

The hollow fiber-based cold air microplasma jet array running at atmospheric pressure has been designed to inactivate Pseudomonas fluorescens (P. fluorescens) cells in vitro in aqueous media. The influences of electrode configurations, air flow rate, and applied voltage on the discharge characteristics of the single microplasma jet operating in aqueous media are presented, and the bactericidal efficiency of the hollow fibers-based and large-volume microplasma jet array is reported. Optical emission spectroscopy is utilized to identify excited species during the antibacterial testing of plasma in solutions. These well-aligned and rather stable air microplasma jets containing a variety of short-lived species, such as OH and O radicals and charged particles, are in direct contact with aqueous media and are very effective in killing P. fluorescens cells in aqueous media. This design shows its potential application for atmospheric pressure air plasma inactivation of bacteria cells in aqueous media.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Osmotic potential calculations of inorganic and organic aqueous solutions over wide solute concentration levels and temperatures

Purpose: To demonstrate that the authors’ new “aqueous solution vs pure water” equation to calculate osmotic potential may be used to calculate the osmotic potentials of inorganic and organic aqueous solutions over wide ranges of solute concentrations and temperatures. Currently, the osmotic potentials of solutions used for medical purposes are calculated from equations based on the thermodynamics of the gas laws which are only accurate at low temperature and solute concentration levels. Some solutions used in medicine may need their osmotic potentials calculated more accurately to take into account solute concentrations and temperatures. Methods: The authors experimented with their new equation for calculating the osmotic potentials of inorganic and organic aqueous solutions up to and beyond body temperatures by adjusting three of its factors; (a) the volume property of pure water, (b) the number of “free” water molecules per unit volume of solution, “N{sub f},” and (c) the “t” factor expressing the cooperative structural relaxation time of pure water at given temperatures. Adequate information on the volume property of pure water at different temperatures is available in the literature. However, as little information on the relative densities of inorganic and organic solutions, respectively, at varying temperatures needed to calculate N{sub f} was available, provisional equations were formulated to approximate values. Those values together with tentative t values for different temperatures chosen from values calculated by different workers were substituted into the authors’ equation to demonstrate how osmotic potentials could be estimated over temperatures up to and beyond bodily temperatures. Results: The provisional equations formulated to calculate N{sub f}, the number of free water molecules per unit volume of inorganic and organic solute solutions, respectively, over wide concentration ranges compared well with the calculations of N{sub f} using recorded relative density data at 20 °C. They were subsequently used to estimate N{sub f} values at temperatures up to and excess of body temperatures. Those values, together with t values at temperatures up to and in excess of body temperatures recorded in the literature, were substituted in the authors’ equation for the provisional calculation of osmotic potentials. The calculations indicated that solution temperatures and solute concentrations have a marked effect on osmotic potentials. Conclusions: Following work to measure the relative densities of aqueous solutions for the calculation of N{sub f} values and the determination of definitive t values up to and beyond bodily temperatures, the authors’ equation would enable the accurate estimations of the osmotic potentials of wide concentrations of aqueous solutions of inorganic and organic solutes over the temperature range. The study illustrates that not only solute concentrations but also temperatures have a marked effect on osmotic potentials, an observation of medical and biological significance.

62 RADIOLOGY AND NUCLEAR MEDICINE↗