Hydrated Electron Research Articles

Optical properties of water relaxing after intense laser exposure

The dynamics of the optical properties of water bulk exposed to femtosecond radiation (Ti-sapphire laser, wavelength 800 nm, intensity ∼ 10 13 W / c m 2 ) was studied in the time window of ≈ 1.5 n s using a pump–probe technique. Both the refractive index and absorbance were measured by femtosecond interferometric microscopy, which allowed us to gather deconvoluting quantitative data about the induced processes: solvation of excess electrons, geminate recombination, and development of cavitation. We found that the number of electrons produced by a strong, near infrared (NIR) field in the cavitation regime ( < 10 19 c m − 3 ) is much lower than was previously thought. The obtained data clarify the mechanisms of laser energy deposition in water and are of crucial importance to understand intensive light action on aqueous-based systems.

Abstract 482: Multiple chemical action cancer therapeutics

Abstract Radiation-produced quasi-free electrons (i.e., low energy electrons in solutions) causes DNA damage. However, there are no evidence that radiation-produced partially solvated electrons (i.e., presolvated or, prehydrated electrons) and fully solvated electrons (i.e., aqueous or solvated electrons) cause strand breaks. However, recent work on azidoDNA-model systems show that radiation-produced electrons can be converted to highly damaging aminyl radicals (RNH•) which do have the potential to cause strand breaks. Experimental studies in our labs (both in vitro and in vivo) have shown that 2-deoxy-D-glucose (2-DG), a glucose mimic and glycolytic inhibitor, enhances radiation-induced damage selectively in tumor cells while protecting normal cells and against infection. Thereby suggesting that 2-DG can be used as a differential radiomodifier to improve the efficacy of cancer radiotherapy. Based on these experimental results and data mining models, we show that the azido derivative of 2DG; 2-Azido-2-deoxy-D-glucose (2-AZ-2-DG) has unique azido chemistries. The neutral aminyl radical produced from 2-AZ-2-DG under reductive environment undergoes facile conformational change from the stable chair form to the reactive boat form. Subsequently, this aminyl radical causes H-atom abstraction from C5 of the sugar moiety via proton-coupled electron transfer process. Further, a promise as multivalent drug to augment multipronged cellular damage including site-specific DNA radiation damage and also counter infections persisting in several cancer cases. Our long range goals are to harness these unique chemistries in gold based nanotools for X-PDT (X-ray induced photodynamic therapy). Citation Format: Rao Papineni, Amithava Adhikary. Multiple chemical action cancer therapeutics [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 482.

Water mediated electron attachment to nucleobases: Surface-bound vs bulk solvated electrons.

We have presented a mechanism for electron attachment to solvated nucleobases using accurate wave-function based hybrid quantum/classical (QM/MM) simulations and uracil as a test case. The initial electron attached state is found to be localized in the bulk water, and this water-bound state acts as a doorway to the formation of the final nucleobase bound state. The electron transfer from water to uracil takes place because of the mixing of electronic and nuclear degrees of freedom. The water molecules around the uracil stabilize the uracil-bound anion by creating an extensive hydrogen-bonding network and accelerate the rate of electron attachment to uracil. The complete transfer of the electron from water to the uracil occurs in a picosecond time scale, which is consistent with the experimentally observed rate of reduction of nucleobases in the presence of water. The degree of solvation of the aqueous electron can lead to a difference in the initial stabilization of the uracil-bound anion. However, the anions formed due to the attachment of both surface-bound and bulk-solvated electrons behave similarly to each other at a longer time scale.

Ab Initio Molecular Dynamics Simulations of Solvated Electrons in Ammonia Clusters.

We investigated excess electron solvation dynamics in (NH3)n– ammonia clusters in the n = 8–32 size range by performing finite temperature molecular dynamics simulations. In particular, we focused on three possible scenarios. The first case is designed to model electron attachment to small neutral ammonia clusters (n ≤ ∼10) that form hydrogen-bonded chains. The excess electron is bound to the clusters via dipole bound states, and persists with a VDE of ∼160 meV at 100 K for the n = 8 cluster. The coupled nuclear and electronic relaxation is fast (within ∼100 fs) and takes place predominantly by intermolecular librational motions and the intramolecular umbrella mode. The second scenario illustrates the mechanism of excess electron attachment to cold compact neutral clusters of medium size (8 ≤ n ≤ 32). The neutral clusters show increasing tendency with size to bind the excess electron on the surface of the clusters in weakly bound, diffuse, and highly delocalized states. Anionic relaxation trajectories launched from these initial states provide no indication for excess electron stabilization for sizes n < 24. Excess electrons are likely to autodetach from these clusters. The two largest investigated clusters (n = 24 and 32) can accommodate the excess electron in electronic states that are mainly localized on the surface, but they may be partly embedded in the cluster. In the last 500 fs of the simulated trajectories, the VDE of the solvated electron fluctuates around ∼200 meV for n = 24 and ∼500 meV for n = 32, consistent with the values extrapolated from the experimentally observed linear VDE–n–1/3 trend. In the third case, we prepared neutral ammonia cluster configurations, including an n = 48 cluster, that contain possible electron localization sites within the interior of the cluster. Excess electrons added to these clusters localize in cavities with high VDEs up to 1.9 eV for n = 48. The computed VDE values for larger clusters are considerably higher than the experimentally observed photoelectric threshold energy for the solvated electron in bulk ammonia (∼1.4 eV). Molecular dynamics simulations launched from these initial cavity states strongly indicate, however, that these cavity structures exist only for ∼200 fs. During the relaxation the electron leaves the cavity and becomes delocalized, while the cluster loses its initial compactness.

Organocatalyzed Birch Reduction Driven by Visible Light.

The Birch reduction is a powerful synthetic methodology that uses solvated electrons to convert inert arenes to 1,4-cyclohexadienes-valuable intermediates for building molecular complexity. Birch reductions traditionally employ alkali metals dissolved in ammonia to produce a solvated electron for the reduction of unactivated arenes such as benzene (Ered < -3.42 V vs SCE). Photoredox catalysts have been gaining popularity in highly reducing applications, but none have been reported to demonstrate reduction potentials powerful enough to reduce benzene. Here, we introduce benzo[ghi]perylene imides as new organic photoredox catalysts for Birch reductions performed at ambient temperature and driven by visible light from commercially available LEDs. Using low catalyst loadings (<1 mol percent), benzene and other functionalized arenes were selectively transformed to 1,4-cyclohexadienes in moderate to good yields in a completely metal-free reaction. Mechanistic studies support that this unprecedented visible-light-induced reactivity is enabled by the ability of the organic photoredox catalyst to harness the energy from two visible-light photons to affect a single, high-energy chemical transformation.

Ultrafast Dynamics of Water Radiolysis: Hydrated Electron Formation, Solvation, Recombination, and Scavenging.

The ultrafast formation, solvation, and geminate recombination of hydrated electrons upon vacuum ultraviolet photoexcitation of liquid water and the static and dynamic scavenging by NO3- are investigated using femtosecond time-resolved photoelectron spectroscopy. The solvation time constant for excess electrons is typical of that for liquid water but increases slightly with increasing excitation energy. The electron survival probability for geminate recombination is found to be much lower than the literature values owing to previously unobserved ultrafast geminate recombination in a period of 5 ps. NO3- induces the ultrafast (static) scavenging of photoexcited electronic states of liquid water and the dynamic scavenging of detached electrons with a reaction rate that is dependent on the excitation energy. The formation of hydrated electrons at 7.7 eV is ascribed to a H-atom-transfer process, but it is plausible that additional formation channels open at higher energies.

Photoexcitation of Ge9- Clusters in THF: New Insights into the Ultrafast Relaxation Dynamics and the Influence of the Cation.

We present a comprehensive femtosecond (fs) transient absorption study of the [Ge9(Hyp)3]− (Hyp = Si(SiMe3)3) cluster solvated in tetrahydrofuran (THF) with special emphasis on intra- and intermolecular charge transfer mechanisms which can be tuned by exchange of the counterion and by dimerization of the cluster. The examination of the visible and the near infrared (NIR) spectral range reveals four different processes of cluster dynamics after UV (267/258 nm) photoexcitation related to charge transfer to solvent and localized excited states in the cluster. The resulting transient absorption is mainly observed in the NIR region. In the UV-Vis range transient absorption of the (neutral) cluster core with similar dynamics can be observed. By transferring concepts of: (i) charge transfer to the solvent known from solvated Na− in THF and (ii) charge transfer in bulk-like materials on metalloid cluster systems containing [Ge9(Hyp)3]− moieties, we can nicely interpret the experimental findings for the different compounds. The first process occurs on a fs timescale and is attributed to localization of the excited electron in the quasi-conduction band/excited state which competes with a charge transfer to the solvent. The latter leads to an excess electron initially located in the vicinity of the parent cluster within the same solvent shell. In a second step, it can recombine with the cluster core with time constants in the picosecond (ps) timescale. Some electrons can escape the influence of the cluster leading to a solvated electron or after interaction with a cation to a contact pair both with lifetimes exceeding our experimentally accessible time window of 1 nanosecond (ns). An additional time constant on a tens of ps timescale is pronounced in the UV-Vis range which can be attributed to the recombination rate of the excited state or quasi conduction band of Ge9−. In the dimer, the excess electron cannot escape the molecule due to strong trapping by the Zn cation that links the two cluster cores.

The link between electrolytes and metals.

Photoelectron spectroscopy maps a gradual transition for solvated electrons in ammonia

Important components for accurate hyperfine coupling constants: electron correlation, dynamic contributions, and solvation effects

ABSTRACT The calculation of hyperfine coupling constants is a challenging task in balancing accuracy and computational effort. While previous work has shown the importance of electron correlation and molecular dynamic contributions, we present a systematic study simultaneously analyzing the influence of both effects on hyperfine coupling constants. To this end, we thoroughly study two organic radicals, namely the dimethylamino radical and ethanal radical cation, proving the need to account for conformational flexibility as well as the large influence of electron correlation. Based on these results, we analyse the effect of electron correlation and dynamic simulations on a set of 12 organic radicals, illustrating that both effects are vital for an accurate in silico description on the same scale. Furthermore, we study the influence of solvation using the efficient nuclei-selected algorithm to obtain hyperfine coupling constants with electron correlation for large systems, indicating the necessity to include explicit solvent molecules. Finally, we introduce a composite approach to incorporate all contributions for hyperfine coupling of radicals in solution at comparatively low computational cost. This is successfully tested on the hydroxylated TEMPO radical in aqueous solution, where we are able to compute a 14 N-HFCC of 44.4 MHz compared to the experimentally measured 47.6 MHz.

Consecutive Photoinduced Electron Transfer (conPET): The Mechanism of the Photocatalyst Rhodamine 6G.

The dye rhodamine 6G can act as a photocatalyst through photoinduced electron transfer. After electronic excitation with green light, rhodamine 6G takes an electron from an electron donor, such as N,N‐diisopropylethylamine, and forms the rhodamine 6G radical. This radical has a reduction potential of around −0.90 V and can split phenyl iodide into iodine anions and phenyl radicals. Recently, it has been reported that photoexcitation of the radical at 420 nm splits aryl bromides into bromide anions and aryl radicals. This requires an increase in reduction potential, hence the electronically excited rhodamine 6G radical was proposed as the reducing agent. Here, we present a study of the mechanism of the formation and photoreactions of the rhodamine 6G radical by transient absorption spectroscopy in the time range from femtoseconds to minutes in combination with quantum chemical calculations. We conclude that one photon of 540 nm light produces two rhodamine 6G radicals. The lifetime of the photoexcited radicals of around 350 fs is too short to allow diffusion‐controlled interaction with a substrate. A fraction of the excited radicals ionize spontaneously, presumably producing solvated electrons. This decay produces hot rhodamine 6G and hot rhodamine 6G radicals, which cool with a time constant of around 10 ps. In the absence of a substrate, the ejected electrons recombine with rhodamine 6G and recover the radical on a timescale of nanoseconds. Photocatalytic reactions occur only upon excitation of the rhodamine 6G radical, and due to its short excited‐state lifetime, the electron transfer to the substrate probably takes place through the generation of solvated electrons as an additional step in the proposed photochemical mechanism.

Reactivity of solvated electrons in ionic liquid interacting with low-pressure plasmas

We employed charge transfer to the solvent (CTTS) transition to examine the reactivity of solvated electrons in ionic liquid interacting with plasmas. A dye laser pulse at 225 nm was injected into N,N,N-trimethyl-N-propylammonium bis (trifluoromethylsulfonyl) imide with the addition of potassium iodide, which was irradiated with low-pressure plasmas, and the reaction frequency of the solvated electrons produced by the CTTS transition was measured by optical absorption spectroscopy. It was observed that the reaction frequency of solvated electrons was enhanced by plasma irradiation. The enhanced reaction frequency was more remarkable by irradiation of a nitrogen plasma than argon and oxygen plasmas. In addition, a higher reaction frequency was observed at a closer distance from the plasma–liquid interface. The UV–vis absorbance spectrum of the ionic liquid was changed by plasma irradiation, indicating the production of unknown species which had a high reaction frequency with solvated electrons in the ionic liquid.

An electron-capture efficiency in femtosecond filamentation

This paper reveals one of the primary chemical processes in femtosecond filaments. Reduction yields from Eu3+ to Eu2+ by focused femtosecond 800 nm pulses in ethanol solution were determined to be 0.021 (Eu2+ molecule/800 nm photon absorbed) or 0.14 (micro mol/ absorbed laser energy(J)) under single filament conditions. The Eu3+ captured an electron which was formed by filamentation, leading to Eu2+. About half of the solvated electrons that initially survived were estimated to be captured by Eu3+. Halogen ions are found to make a contribution to femtosecond pulse absorption with an increasing tendency with Cl < Br < I.

(Invited) Mechanism of Formic Acid synthesis in low pH during CO2 Reduction via electrified plasma/liquid interface

Electrochemical discharger over liquid water enriched with dissolved carbon dioxide (CO2) is capable of synthesizes formate (HCO2 -) and oxalate (C2O4 2 -), although in very low faradaic selectivity toward organic molecules ca. 9% [1]. The efficient CO2 reduction (CO2-R) toward these organic molecules via electrochemical discharge remains a challenge. This contribution devotes to find possible ways to produce these products efficiently. In this context, the mechanism of electrosynthesis for both formate and oxalate is postulated and used from a theoretical perspective [2] to figure out which parameters are key to reach as maximum selectivity as possible.Figure 1a shows the chemical reaction network (CRN) postulated for CO2-R via electrochemical discharge over water. The discharge promotes a periodic perturbation on the local concentration of the solvated electron within the nanoreactor (volume of less than one nanoliter beneath the plasma liquid interface), firing the set of reaction displayed in this CRN. Three final products are formed, one volatile and two dissolved in the liquid phase. Gaseous hydrogen is a volatile product synthetized majorly via recombination of two solvated electrons, reaction (1); other two routes for hydrogen synthesis described in reference 2 are negligible over uninterrupted long lasting discharge. On the other hand, organic molecules requires the carboxyl radical anion {CO2 -∙ (aq)} as precursor. In view of this CRN, the generalist model in reference (2) were used for implement the algorithm related to the chemical dynamical system. The computational experiments employed Wolfram language, 10- 6 s step, a stationary current at level 9.5 mA (the same used by the researchers in ref 1) and the parameters displayed in table 1. The selectivity toward a given product is the ratio of its quantity of mole with respect to that of injected electrons. Figure 1b shows time evolution for the concentrations of the main reactants, the intermediate (carboxyl radical anion) and the final products. Figure 1c shows the selectivity toward each final product considering two span of continuous stationary discharge.The computational experiments demonstrated that the chemical dynamics driven by a stationary injection of electron (term qe in the model) in water is mostly governed by the formation reaction of CO2 -∙ (aq) within the early 43 ms span of time. Within this period, full content of CO2 in the nanoreactor depletes as result of the fastest reaction rate for the formation of CO2 -∙ (aq) . The large local concentration (“local” qualifies the concentration inside the nanoreactor) of CO2 -∙ (aq) favors the oxalate formation, being the oxalate the major final product. Formate is only synthetized at significant formation rate between 0.040 and 0.043 s, when the concentration of both solvated electrons and CO2 -∙ (aq) start to be less dissimilar as consequence of the depletions of the aqueous CO2 in the nanoreactor. Anytime thereafter, the solvated electrons has increased concentration, and the hydrogen passes to form majorly. Considering the 300,000 s (5 minutes used in reference 1), about 7.72% faradaic efficiency toward organic molecules is obtained, corroborating the low efficiency for experiments in real life.In conclusion, this work postulate the mechanism of CO2 reduction via electrochemical discharge, and it suggests the employment of short span of stationary discharge to obtain faradaic efficiency toward organic molecules of 98.46%, being 96.89% selective toward oxalate. Figure 1: (a) postulated chemical reaction network for CO2-R via electrochemical discharge over water, (b) time evolutions for the concentrations of either reactants or products , and (c) selectivity toward formate (yellow), oxalate (orange) and hydrogen (pink) at STP CO2 saturation. Table 1: parameters for solving the dynamical model [3] Parameter Value Unit Ref k1 6.0×109 L mol−1 s−1 3 k2 9.0×109 L mol−1 s−1 3 k3 1.0×1010 L mol−1 s−1 3 k4 1.26×109 L mol−1 s−1 3 qe (9.5 mA) 98.46×10-9 mol s- 1 1 V 2.36×10-9 L 2 [H+]0 1.00×10-7 mol L-1 [CO2]0 40.00×10-3 mol L-1 References [1]Rumbach, P., R. Xu, and D.B. Go, Electrochemical Production of Oxalate and Formate from CO2 by Solvated Electrons Produced Using an Atmospheric-Pressure Plasma. Journal of The Electrochemical Society, 2016. 163(10): p. F1157-F1161.[2] Mota-Lima, A., et al., Electrosynthesis via Plasma Electrochemistry: Generalist Dynamical Model To Explain Hydrogen Production Induced by a Discharge over Water. The Journal of Physical Chemistry C, 2019. 123(36): p. 21896-21912.[3] Neta, P., J. Grodkowski, and A.B. Ross, Rate Constants for Reactions of Aliphatic Carbon‐Centered Radicals in Aqueous Solution. Journal of Physical and Chemical Reference Data, 1996. 25(3): p. 709-1050. Figure 1

Isolating Organic Half-Reaction Products in Aqueous Solutions Exposed to Nonthermal Plasma

Aqueous media that have been activated by nonthermal plasma operating at atmospheric pressure have attracted interest for biomedical, agricultural, and nanomaterial synthesis applications. Atmospheric pressure plasmas generated with noble gases have been shown to inject free electrons from the gas phase into the aqueous phase, wherein they become solvated. These solvated electrons can create a chemically reducing environment capable of promoting electrochemical reactions. In order to maintain charge neutrality within the solution, the observed reduction half-reaction must be balanced by an oxidation half-reaction occurring elsewhere in the solution. In applications where isolation of the reduction and/or oxidation products is important, such as pharmaceutical synthesis, mass transport between the two half-reactions must be controlled. Isolation of products is relatively straightforward for plasma-assisted electrochemistry, where the half-reactions occur in compartments that are separated by a salt bridge, and each compartment contains either a metal electrode or microplasma. Product separation becomes more complex in the case of electrodeless systems, such as those using plasma jets impinging upon aqueous solutions. Not only are the locations of the half-reactions ill-defined, but they are occurring in the same volume. In this work, the spatial reduction potential profile of solutions containing molecular probes in contact with an atmospheric pressure plasma jet is used to identify the boundary of the two half-reactions. The transport of a molecular probe through the boundary separating the electrodeless cathode from the electrodeless anode was controlled, and the concentration of oxidized and reduced forms of the molecule on either side of the boundary were quantified via a colorimetric assay. The efficacy of the product isolation strategy for electrodeless plasma electrochemical systems will be discussed.

(Invited) Catalyst-Free, Plasma-Driven Electrolytic Synthesis of Ammonia from Nitrogen and Water at Ambient Conditions

A plasma-driven electrolytic process has been developed to produce ammonia from nitrogen and water at ambient conditions. The system features a direct-current, atmospheric-pressure microplasma formed in a flow of nitrogen at the surface of an aqueous, acidic solution. By comparing ammonia yield against experimental controls, including argon gas, and measuring ammonia yield as a function of time, discharge current and solution pH, we show the faradaic efficiency reaches as high as 100%. We also uncover insights into the reaction mechanism by utilizing scavengers, which involves solvated electrons and hydrogen radicals preferentially reacting with nitrogenated species. We anticipate this technology will be promising for distributed ammonia production since it can operate at ambient conditions with only electricity, acidified water, and nitrogen gas as feedstocks.

Plasma-molten Metal and/or Liquid Interactions for Materials/Chemical Processing

Several grand challenges in energy storage and conversion need the discovery of functional materials that many agree will be composed of complex compositions at nanoscale. In this regard, plasma based materials processing has been shown to be promising for combinatorial techniques and scalable processing. The use of plasma oxidation of liquid precursors allows for creation of metastable complex oxide particles with compositional control.1 A number of examples will be discussed in which the above two techniques are currently being used for accelerating the development of a variety of catalysts including electrocatalysts and materials for storage applications.This talk will highlight our efforts to understand the role of plasmas under two categories: (a) the synergistic effects hydrogen and nitrogen plasma interactions with molten metals;2 and (b) the oxygen plasma-liquid droplet interactions.3 To gain insights into these mechanisms we have studied the interaction of hydrogen and nitrogen plasmas with low melting point metals, primarily with gallium. Absorption/desorption experiments as well as theoretical-computational calculations were performed. Experiments have shown an increment of adsorbed gaseous species into the molten metal in the presence of plasmas. In the case of oxygen plasma-liquid droplet interactions for creating complex oxides, the role of solvated electrons, oxygen radicals and heating effects will be discussed. Finally, the use of plasmas for achieving liquid phase epitaxial growth of GaN and related materials will be discussed.4 Author acknowledge primary funding support from NSF Solar Project (DMS 1125909), and NSF EPSCoR (1355438).

Understanding the Chemistry and Physics of Charge Transfer in Electrolysis with a Plasma Electrode

Plasma electrochemistry consists of an electrolytic cell where the cathode or the anode is replaced by a direct current (DC) plasma. Unlike conventional electrolysis, where reactions depend on the catalytic properties of the electrode, highly reactive species including solvated electrons (e- aq), hydroxyl radicals (•OH) and atomic hydrogen (H•) are introduced into, or are generated in, the volume of the liquid. This novel interfacial interaction has led to a variety of applications including the chemical analysis of dissolved elements in an aqueous sample, the synthesis of both nanomaterials and useful chemicals, and the destruction of organic contaminants for water purification. With reported faradaic efficiencies greater than 100%, plasma electrolysis is a compelling alternative to conventional electrolysis. However, there are many things that are not understood about the charge transfer process, particularly when the plasma serves as the anode in the electrolytic cell. This includes how these chemical species are generated and in what amounts, as well as how electrons are emitted from the liquid into the plasma (in a process called secondary emission) to complete the electrolytic circuit. In this work we use the plasma voltage and breakdown voltage to study electron emission and show that emitted electrons are never solvated, or even pre-solvated, and are independent of the liquid chemistry. We find that secondary emission is very inefficient, with roughly 1 out of a million electrons escaping the solution. Finally, reactions with chloroacetate and chloroacetic acid were used to narrow down the potential yields of each of the chemical species and refine our understanding of the faradaic efficiency.

Destruction of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment.

Ultraviolet photochemical reaction of sulfite (SO32-) photosensitizer generates strongly reducing hydrated electrons (eaq-; NHE = -2.9 V) that have been shown to effectively degrade individual per- and polyfluoroalkyl substances (PFASs), including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). However, treatment of complex PFAS mixtures in aqueous film-forming foam (AFFF) remains largely unknown. Here, UV-sulfite was applied to a diluted AFFF to characterize eaq- reactions with 15 PFASs identified by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) targeted analysis. Results show that reactivity varies widely among PFASs, but reaction rates observed for individual PFASs in AFFF are similar to rates observed in single-solute experiments. While some structures, including long-chain perfluoroalkyl sulfonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs) were readily degraded, other structures, most notably short-chain PFSAs and fluorotelomer sulfonic acids (FTSs), were more recalcitrant. This finding is consistent with results showing incomplete fluoride ion release (up to 53% of the F content in AFFF) during reactions. Furthermore, results show that selected PFSAs, PFCAs, and FTSs can form as transient intermediates or unreactive end-products via eaq- reactions with precursor structures in AFFF. These results indicate that while UV-sulfite treatment can be effective for treating PFOS and PFOA to meet health advisory levels, remediation of the wider range of PFASs in AFFF will prove more challenging.

Crucial role of cyanides for high-potential electrochemical reduction reaction

Despite the potential of organic materials for cathodes in lithium-ion batteries arising from their eco-friendly production processes and structural flexibility, their redox properties are not comprehensively unveiled. In this work, the redox properties and performances for chloranil derivatives with one to four cyano functional group(s) are studied to assess their potential as high-potential organic cathode materials. The well-designed computational protocol is employed to reliably predict the redox behaviors for the organic compounds. This investigation highlights synergistic effects of carbonyls and cyanides on improving the electrochemical properties, exhibiting the remarkably high open-circuit redox potential (4.50 ​V vs. Li/Li+) and theoretical performances (515 ​mA ​h/g and 1517 ​mWh/g) for the chloranil derivative with four cyano functionalities. Furthermore, this study emphasizes that the redox potential of a chloranil derivative strongly relies not only on its structural variation but also on the Li-involved discharging process, electronic properties, and, most importantly, “solvation energy”. A universal correlation of redox potential with electron affinity and solvation energy addresses that chloranils would experience two-stage transition behaviors during the discharging process, implying a critical role of solvation energy in their cathodic deactivation and thus suggesting a smart approach for the systematic design of high-performance organic cathodes. Electrostatic potential maps unambiguously describe the change in the reductive ability of a chloranil derivative during the Li-involved discharging process.

Interactions of Solvated Electrons with Nucleobases: The Effect of Base Pairing.

We have investigated the effect of base pairing on the electron attachment to nucleobases in bulk water, taking the guanine-cytosine (GC) base pair as a test case. The presence of the complementary base reinforces the stabilization effect provided by water and preferentially stabilizes the anion by hydrogen bonding. The electron attachment in bulk-solvated GC happens through a doorway mechanism, where the initial electron attached state is water bound, and it subsequently gets converted to a GC bound state. The additional electron in the final GC bound state is localized on the cytosine, similar to that in the gas phase. The transfer of the electron from the initial water-bound state to the final GC bound state happens due to the mixing of electronic and nuclear degrees of freedom and takes place at a picosecond time scale.