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  1. Ionic Liquid-Enhanced Interfaces to Boost Reactive CO2 Capture

    Thorat, Amey S. ; Sartape, Rohan ; Chauhan, Rohit ; ... - Journal of Physical Chemistry. B
    The addition of ionic liquids (ILs) to a mixture containing a molecular solvent and other ionic species can induce the heterogeneous redistribution of cations and anions at the gas–liquid interface. This nonuniform redistribution of cations and anions driven by the differences in the solvophilicity of ions can improve the thermophysical and interfacial properties of such mixtures, creating a local chemical environment that is conducive to some reactions. In this work, ILs are added to a mixture of potassium hydroxide (KOH) and ethylene glycol (EG), used as a reactive absorbent and electrolyte in the migration-assisted moisture-gradient (MAMG) process for CO2 capture.more » Molecular dynamics (MD) simulations are employed to probe into the effects of complex ion–ion and ion–solvent interactions and to examine the chemical composition at the gas–liquid interface. A total of 12 systems are investigated using molecular simulations to identify trends in the performance of IL additives based on the choice of cation, anion, and IL concentration. The cation effects are studied using IL additives based on 1-ethyl-3-methylimidazolium ([EMIM]+) and 1-butyl-3-methylimidazolium ([BMIM]+), while the impact of anions is examined using additives based on dicyanamide [DCA]−, triflate [TfO]−, bistriflimide [NTf2]−, and hexafluorophosphate [PF6]− anions, respectively. The influence of the IL concentration is also evaluated at molar concentrations between 1% and 4%. The simulation results indicate that the use of IL additives can affect the physical CO2 solubility, surface tension, and the localization of CO2 around the [OH]− ions at the gas–liquid interface. It is also evident that the choice of cations, anions, and IL concentration determines the extent to which the IL additives impact the local physicochemical properties. Physical dissolution, diffusive transport, and interaction with [OH]− are critical intermediate steps toward reactive CO2 capture using a liquid absorbent. Hence, the improvement in one or more of these properties, aided by IL additives, is expected to improve the overall CO2 capture performance. Experiments reaffirmed the impact of IL additives on CO2 capture performance and the sensitivity to the choice of the cation, anion, and concentration of the IL additive.« less

  2. Neutron skins: A perspective from dispersive optical models

    Atkinson, M. C. ; Dickhoff, W. H. - Frontiers in Physics
    An overview of neutron skin predictions obtained using an empirical nonlocal dispersive optical model (DOM) is presented. The DOM links both scattering and bound-state experimental data through a subtracted dispersion relation which allows for fully consistent, data-informed predictions for nuclei where such data exist. Large skins were predicted for both 48Ca ( R$$^{48}_{skin}$$ = 0.25 ± 0.023 fm in 2017) and 208Pb (R$$^{208}_{skin}$$) = 0.25 ± 0.05 fm in 2020). Whereas the DOM prediction in 208Pb is within 1σ of the subsequent PREX-2 measurement, the DOM prediction in 48Ca is over 2σ larger than the thin neutron skin resulting frommore » CREX. From the moment it was revealed, the thin skin in 48Ca has puzzled the nuclear-physics community as no adequate theories simultaneously predict both a large skin in 208Pb and a small skin in 48Ca. The DOM is unique in its ability to treat both structure and reaction data on the same footing, providing a unique perspective on this Rskin puzzle. It appears vital that more neutron data be measured in both the scattering and bound-state domain for 48Ca to clarify the situation.« less

  3. Elucidating the Mechanism of Large Phosphate Molecule Intercalation Through Graphene-Substrate Heterointerfaces

    Liang, Jiayun ; Ma, Ke ; Zhao, Xiao ; ... - ACS Applied Materials and Interfaces

  4. Spectroscopic and Chemical Properties of Ionic Liquids: Computational Study

    Kim, Hyung J. - Chemical Record
    A brief account is given of highlights of our computational efforts – often in collaboration with experimental groups – to understand spectroscopic and chemical properties of ionic liquids (ILs). Molecular dynamics, including their inhomogeneous character, responsible for key spectral features observed in dielectric absorption, infra-red (IR) and fluorescence correlation spectroscopy (FCS) measurements are elucidated. Mechanisms of chemical processes involving imidazolium-based ILs are illustrated for CO2 capture and related reactions, transesterification of cellulose, and Au nanocluster-catalyzed Suzuki cross-coupling reaction with attention paid to differing roles of IL ions. A comparison with experiments is also made.

  5. Tunable Repression of Key Photosynthetic Processes Using Cas12a CRISPR Interference in the Fast-Growing Cyanobacterium Synechococcus sp. UTEX 2973

    Knoot, Cory J. ; Biswas, Sandeep ; Pakrasi, Himadri B. - ACS Synthetic Biology
    Cyanobacteria are photoautotrophic prokaryotes that serve as key model organisms to study basic photosynthetic processes and are potential carbon-negative production chassis for commodity and high-value chemicals. The development of new synthetic biology tools and improvement of current ones is a requisite for furthering these organisms as models and production vehicles. CRISPR interference (CRISPRi) allows for targeted gene repression using a DNase-dead Cas nuclease (“dCas”). Here, we describe a titratable dCas12a (dCpf1) CRISPRi system and apply it to repress key photosynthetic processes in the fast-growing cyanobacterium Synechococcus sp. UTEX 2973 (S2973). The system relies on a lac repressor system that retainsmore » tight regulation in the absence of inducer (0–10% repression) while maintaining the capability for >90% repression of high-abundance gene targets. We determined that dCas12a is less toxic than dCas9. We tested the efficacy of the system toward eYFP and three native targets in S2973: the phycobilisome antenna, glycogen synthesis, and photosystem I (PSI), an essential part of the photosynthetic electron transport chain in oxygenic photoautotrophs. PSI was knocked down indirectly by repressing the protein factor BtpA involved in stabilizing core PSI proteins. We could reduce cellular PSI titer by 87% under photoautotrophic conditions, and we characterized these cells to gain insights into the response of the strain to the low PSI content. The ability to tightly regulate and time the (de)repression of essential genes in trans will allow for the study of photosynthetic processes that are not accessible using knockout mutants.« less

  6. Action levels for airborne uranium in the workplace: chemical and radiological assessments

    Leggett, Richard Wayne ; Meck, Robert A. - Journal of Radiological Protection
    In this study, a method is described for deriving two levels of action—an investigation level (IL) and an immediate action level (IAL)—for different forms and mixtures of the natural uranium (U) isotopes 234U, 235U, and 238U in air in the workplace. An IL indicates the need to confirm the validity of moderately elevated measurements of airborne U and adequacy of confinement controls and determine whether work limitations are appropriate. An IAL indicates that safeguards should be put into place immediately, including removal of workers from further exposure until conditions are acceptable. Derivations of ILs and IALs are based on latestmore » radiation protection guidance, information on chemical toxicity of U, and biokinetic models for U. An action level (IL or IAL) is the more restrictive of two derived values, the action level based on U as a chemical hazard and the action level based on U as a radiation hazard.« less

  7. Analytical transport network theory to guide the design of 3-D microstructural networks in energy materials: Part 2. Flow with reactions

    Cocco, Alex P. ; Chiu, Wilson K.S. - Journal of Power Sources
    Here we extend the fully analytical, heuristic “Analytical Transport Network Model” for steady-state, diffusive flow in a 3-D network to account for surface reactions. In the limit of negligible reactions, the model reduces to the conserved flow solution. The extension does not increase the time required to run the model, which in Part 1 was shown to be 0.5–1.5 and 5–6 orders of magnitude faster than electrochemical fin (ECF) theory and finite element analysis (FEA) for conserved flow, respectively. The model is compared to reacting-flow ECF and FEA as well as to experiments and is demonstrated as a potentially usefulmore » heuristic for understanding the influence of morphology and topology on reactive-diffusive flow through a 3-D microstructural network.« less
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