Reaction Of Solvated Electrons Research Articles

Creation and Reaction of Solvated Electrons at and near the Surface of Water.

Solvated electrons (es-) are among nature's most powerful reactants, with over 2600 reactions investigated in bulk water. These electrons can also be created at and near the surface of water by exposing an aqueous microjet in vacuum to gas-phase sodium atoms, which ionize into es- and Na+ within the top few layers. When a reactive surfactant is added to the jet, the surfactant and es- become coreactants localized in the interfacial region. We report the reaction of es- with the surfactant benzyltrimethylammonium in a 6.7 M LiBr/water microjet at 235 K and pH = 2. The reaction intermediates trimethylamine (TMA) and benzyl radical are identified by mass spectrometry after they evaporate from solution into the gas phase. Their detection demonstrates that TMA can escape before it is protonated and benzyl before it combines with itself or a H atom. Diffusion-reaction calculations indicate that es- reacts on average within 20 Å of the surface and perhaps within the surfactant monolayer itself, while unprotonated TMA evaporates from the top 40 Å. The escape depth exceeds 1300 Å for the more slowly reacting benzyl radical. These proof-of-principle experiments establish an approach for exploring the near-interfacial analogues of aqueous bulk-phase radical chemistry through the evaporation of reaction intermediates into the gas phase.

Direct Observation of Solvated Electrons in Deep Eutectic Solvents: Efficient Capture of Presolvated Electrons by DNA Base.

The solvated electron being the simplest form of an extremely reactive intermediate is of great fundamental interest in chemistry, physics, and biology since its discovery. Recently, deep eutectic solvents (DESs) have been in focus as biodegradable and cost-effective alternative to ionic liquids (ILs) for different applications. These include areas where electron transport and transfer processes are involved. Herein, we present the first report on the existence, yield, and properties of solvated electrons in three deep eutectic solvents, reline, ethaline, and glyceline, composed of choline chloride as a hydrogen bond acceptor and urea, ethylene glycol, and glycerol (Gly) as hydrogen bond donors, respectively, at a molar ratio of 1:2. The varied transient absorption spectra of solvated electrons in these DESs have been explained on the basis of polarity, hydrogen-bonding effect, and the moieties responsible for creating the environment for solvation. The yield and average lifetime follow the trends in viscosity as well as the reactivity of electrons with the components. The C37 value, a measure of the efficiency of scavenging presolvated electrons, is the highest in ethaline in the case of nitrate ions, which indicates the slowest solvation process in this DES. The presolvated electron capture by a DNA base, an aspect considered to be important in cancer radiotherapy, could be monitored conveniently in these liquids at a much longer time scale compared to that reported in aqueous solutions. Bimolecular rate constants for the reaction of solvated electrons with nitrate and the DNA base have been calculated and compared in the three DESs. Unlike in ILs, these experimentally obtained values are comparable to the diffusion-controlled rate constants in DESs.

A pulsed electron beam synthesis of PEDOT conducting polymers by using sulfate radicals as oxidizing species

In this study, an original radiolytic method, based on pulsed electron beam irradiation, is used for the synthesis of conducting PEDOT in an aqueous solution containing EDOT monomers in the presence of potassium persulfate, K2S2O8, at 0°C. At this low temperature, EDOT monomers are not chemically oxidized by S2O82− anions, initiating PEDOT polymerization, but are rather oxidized by sulfate radicals, SO4•−, which are radiolytically generated by the reaction of solvated electrons, produced by water radiolysis, with persulfate anions. Successfully, as demonstrated by UV–vis absorption spectrophotometry and ATR-FTIR spectroscopy, irradiating the aqueous solution, by using a series of accumulated electron pulses, enables complete EDOT oxidation and quantitative in situ PEDOT polymerization through a step-by-step oxidation mechanism. The morphology of PEDOT polymers, mixed with unreacted K2S2O8 salt, is characterized by Cryo-TEM microscopy in aqueous solution and by SEM after deposition. Successfully, in the absence of any washing step, high resolution AFM microscopy, coupled with infrared nanospectroscopy, is used to discriminate between the organic polymers and the inorganic salt and to probe the local chemical composition of PEDOT nanostructures. The results demonstrate that PEDOT polymers form globular self-assembled nanostructures which preferentially adsorb onto unreacted K2S2O8 solid nanoplates. The present results first demonstrate the efficiency of sulfate radicals as oxidizing species for the preparation of nanostructured PEDOT polymers and second highlight the promising potentiality of electron accelerators in the field of conducting polymers synthesis.

Pulse radiolysis and spectrophotometric studies on the binding of organic cations with heparin

Here we present the spectroscopic and pulse radiolysis studies of the interactions of heparin and some organic cations:methylene blue (MB), 1-methylnicotinamide (MNA+), and its dimer 1,3-bis(1-methylnicotinamide)propane (bis(MNA+)).The interaction between heparin and some cationic dyes (e.g. methylene blue) in aqueous solution leads to the changes in the absorption spectra of those dyes. This effect, called metachromasia, has been successfully used to study the interactions of a number of cationic dyes with heparin and other glycosaminoglycans.Using methylene blue, as a model compound, we have shown that the changes in the rate constant for the reaction of solvated electrons with cationic dye in the presence of heparin (pulse radiolysis) are well correlated with the accompanying changes in the absorption spectra (metachromasia). The same mathematical formalism was applied to absorption and rate constants changes. Using such formalism, we have determined the total number of binding sites per heparin molecule and the equilibrium constants for MNA+ and bis(MNA+).

Reactions of ligands from BT(B)P family with solvated electrons and benzophenone ketyl radicals in 1-octanol solutions. Pulse radiolysis study

Pulse radiolysis involving reactions of solvated electrons and benzophenone ketyl radicals in 1-octanol with selected compounds from bis-triazinyl pyridines and bis-triazinyl bipyridines, BT(B)P family, developed for extraction of trivalent actinides have been studied. The designated ligands were: 2,6-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo-[1,2,4]triazin-3-yl)pyridine, 6,6′-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo-[1,2,4-]triazin-3-yl)-[2,2′]bipyridine, 6,6′-bis(5,6-diethyl-[1,2,4]triazin-3-yl)-[2,2′]bipyridine and 6,6′-bis(5,6-dipentyl-[1,2,4]triazin-3-yl)-[2,2′]bipyridine. Reactions of the ligands with solvated electrons in 1-octanol are fast. The rate constants were determined as equal to: $$ k_{{{\text{CyMe}}_{4} {\text{BTP}}}} . $$ = (2.4 ± 0.2) × 109 dm3 mol−1 s−1, $$ k_{{{\text{CyMe}}_{ 4} {\text{BTBP}}}} $$ = (1.7 ± 0.3) × 109 dm3 mol−1 s−1, $$ k_{{{\text{C}}_{ 2} {\text{BTBP}}}} $$ = (1.3 ± 0.3) × 109 dm3 mol−1 s−1 and $$ k_{{{\text{C}}_{ 5} {\text{BTBP}}}} $$ = (1.7 ± 0.3) × 109 dm3 mol−1 s−1. Reactions of the ligands with benzophenone ketyl radicals are much slower and the measured rate constants were as follows: $$ k_{{{\text{CyMe}}_{ 4} {\text{BTP}}}} $$ = 6.7 × 107 dm3 mol−1 s−1 and $$ k_{{{\text{CyMe}}_{ 4} {\text{BTBP}}}} $$ = 3.2 × 107 dm3 mol−1 s−1.

Electron Beam Mediated Simple Synthetic Route to Preparing Layered Zinc Hydroxide

We have developed a novel and eco-friendly synthetic route for the preparation of a two-dimensional layered zinc hydroxide with intercalated nitrate anions. The layered zinc hydroxide nitrate, called 'zinc basic salt', was, in general, successfully synthesized, using an electron beam irradiation technique. The 2-propanol solutions containing hydrated zinc nitrate were directly irradiated with an electron-beam at room temperature, under atmospheric conditions, without stabilizers or base molecules. Under electron beam irradiation, the reactive OH radicals were generated by radiolysis of water molecules in precursor metal salts. After further radiolytic processes, the hydroxyl anions might be formed by the reaction of solvated electrons and the OH radical. Finally, the was precipitated by the reaction of zinc cation and hydroxyl anions. Structure and morphology of obtained compounds were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and high resolution transmission electron microscopy (HR-TEM). The chemical components of the products were determined by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA). The thermal behavior of products was studied by thermogravimetric (TG) and differential thermal analysis (DTA).

Reactions of Solvated Electrons Initiated by Sodium Atom Ionization at the Vacuum-Liquid Interface

Solvated electrons are powerful reagents in the liquid phase that break chemical bonds and thereby create additional reactive species, including hydrogen atoms. We explored the distinct chemistry that ensues when electrons are liberated near the liquid surface rather than within the bulk. Specifically, we detected the products resulting from exposure of liquid glycerol to a beam of sodium atoms. The Na atoms ionized in the surface region, generating electrons that reacted with deuterated glycerol, C(3)D(5)(OD)(3), to produce D atoms, D(2), D(2)O, and glycerol fragments. Surprisingly, 43 ± 4% of the D atoms traversed the interfacial region and desorbed into vacuum before attacking C-D bonds to produce D(2).

Trimethoprim: Kinetic and mechanistic considerations in photochemical environmental fate and AOP treatment

Trimethoprim (TMP), a bacteriostatic antibiotic, has recently been detected in wastewater and surface waters. In this study the sunlight mediated photochemical fate, and treatment using advanced oxidation and reduction (free radical) processes, have been investigated with respect to their effect on TMP. Photochemical fate, in the presence of humic acid, and advanced oxidation treatment both involve the hydroxyl radical ( OH) as one of the reactive species of interest. Another reactive oxygen species, singlet oxygen ( 1O 2), may also be important in the photochemical fate of TMP. The bimolecular reaction rate constants of TMP with 1O 2 and OH were evaluated to be (3.2 ± 0.2) × 10 6 M −1 s −1 and 8.66 × 10 9 M −1 s −1, respectively. The reaction kinetics for the sub-structural moieties of TMP, 1,2,3-trimethoxybenzene (TMBz) and 2,4-diaminoprimidine (DAP), was evaluated to facilitate an understanding of the loss mechanisms. For TMBz and DAP the reaction rate constants with 1O 2 were <1.0 × 10 4 and (3.0 ± 0.1) × 10 6 M −1 s −1, while with OH they were 8.12 × 10 9 and 1.64 × 10 9 M −1 s −1, respectively. The data suggests that the 1O 2 attacks the DAP and the OH radical attacks the TMBz moiety. However, for TMP, 1O 2 and OH reactions accounted for only ∼19% and ∼6%, of its total photodegradation, respectively. Therefore, the reaction of TMP with excited state natural organic matter is postulated as a significant degradation pathway for the loss of TMP in sunlit waters containing natural organic matter. There was no effect of pH on the direct or indirect photolysis of TMP. To complete the study for reductive treatment processes, the solvated electron reaction rates for the destruction of TMP, TMBz and DAP were also evaluated. The absolute bimolecular reaction rates obtained were, (13.6 ± 0.01) × 10 9, (6.36 ± 0.11) × 10 7 and (10.1 ± 0.01) × 10 9 M −1 s −1, respectively.

Length and Time-Dependent Rates in Diffusion-Controlled Reactions with Conjugated Polymers

Rate constants for diffusion-controlled reactions of solvated electrons with conjugated fluorene oligomers (oF) and polymers (pF) were measured in liquid tetrahydrofuran (THF). Preparative gel permeation chromatography (GPC) was used to separate the polyfluorenes into fractions having narrowed distributions of lengths. Both oF and pF's were used in determinations of the attachment rate constants k(inf) as a function of length, where k(inf) refers to the rate coefficients at long times where they are indeed constant. The results find that in going from oF(1) to pF(133), k(inf) increases by a factor of 16, which is much smaller than that of the 133-fold increase in length. The extent of this increase and its change with length are in excellent agreement with published theoretical models that describe diffusion to long thin objects as either prolate spheroids or one-dimensional arrays of spheres. As the concentration of polymer was increased, the effects of large transient terms in the rate constant were observed. As predicted by the Smoluchowski diffusion equation, with modifications by more contemporary theorists, these transient effects are larger and persist to longer times for the larger molecules. For the longest molecule, pF(133), k(t) increases by more than a decade at short times. In that case, the "transient term" becomes dominant and the rate coefficient is approximately proportional to the square of the effective reaction radius in contrast to the linear dependence usual for diffusional reactions. The size of these transient effects and their quantitative confirmation are unprecedented.

Solvent effects on reactivity of solvated electrons with ammonium nitrate in 2-propanol/water mixed solvents

The solvent effects on reactivity of solvated electrons ( e s − ) with ammonium nitrate were studied in 2-propanol/water mixed solvents as a function of solvent composition and temperature. The kinematic viscosities and densities of these mixed solvents were measured as a function of solvent composition and temperature, and the electrical conductances of ammonium nitrate in the mixed solvents were also measured. The measured rate constants of the nearly diffusion controlled reaction were examined according to the Smoluchowski-type models. These models are useful in evaluating the effects of bulk solvents on reactivity of solvated electrons with charged solutes. In the region of 80–100 mol% water, the rate constants for the reaction [ e s − + ( N O 3 − ) s ] increase with the decrease of viscosity. This indicates that the reaction rates in these solvents correspond well to the Smoluchowski–Stokes model. However in the region of 0–20 mol% water, the rate constant for the reaction [ e s − + ( N H 4 + ) s ] increases with the increase of viscosity. This phenomenon is attributed to the high values of the effective reaction radius ( κR r) for the reaction [ e s − + ( N H 4 + ) s ] in these solvents. The values of κR r (10 −10 m) in the region of 0–20 mol% water are 4.8–5.7, whereas 2.3–2.6 in the region of 80–100 mol% water at 298 K. With the exception of the region from 100 to 93 mol% water, the effective diffusion radius ( R d) decreases with the increase of water content. The activation energies of reaction ( E 2) display having higher values than those of viscosity ( E η ) and conductance ( E Λ 0 ) in the 2-propanol-rich region, while they become lower than both of E η and E Λ 0 in the water-rich region, and converge to similar values in almost pure water.

Reactions of solvated electrons with imidazolium cations in ionic liquids

We examined formation of solvated electrons in several ionic liquids composed of ammonium, pyrrolidinium and piperidinium cations by observing absorption spectra in the visible and near-infrared regions using pulse radiolysi. We also examined reactions of the solvated electrons with imidazolium cations in the ionic liquids. The reaction rate constants were an order of magnitude faster than the diffusion-limited rate calculated from the viscosity. The electrons before full solvation (dry electrons) reacted efficiently with the imidazolium cations. These observations suggest that the electrons in the ionic liquids can move easily before solvation. The scavenging of the dry electron by the imidazolium cation was also examined using C2-alkylated-imidazolium cations. It is found that the alkylation of imidazolium suppresses the reactivity with the dry electron.

The Reaction of Hydrogen Atoms with Methionine Residues: A Model of Reductive Radical Stress Causing Tandem Protein–Lipid Damage

The occurrence of tandem damage, due to reductive radical stress involving proteins and lipids, is shown by using a biomimetic model. It is made of unsaturated lipid vesicle suspensions in phosphate buffer in the presence of methionine, either as a single amino acid or as part of a protein such as RNase A, which contains four methionine residues. The radical process starts with the formation of H(.) atoms by reaction of solvated electrons with dihydrogen phosphate anions, which selectively attack the thioether function of methionine. The modification of methionine to alpha-aminobutyric acid is accompanied by the formation of thiyl radicals, which in turn cause the isomerization of the cis fatty acid residues to the trans isomers. The relationship between methionine modification and lipid damage and some details of the reductive radical stress obtained by proteomic analysis of irradiated RNase A are presented.

Electrochemical behavior of electrodes containing nanostructured carbon of various morphology in the cathodic region of potentials

Voltammograms for electrodes containing nanostructured carbon of various morphology (single-walled carbon nanotubes, filament, columnar structures) are obtained in neutral aqueous electrolytic solutions. Experimental proofs for the existence of injection of solvated electrons into electrolytic solutions at moderate cathodic potentials are presented for all the electrodes. It is established that this effect is connected with the presence of atomically sharp areas on the electrode surfaces. It is assumed that the reason for the appearance of solvated electrons is the autoelectron emission at the interface between the conducting surface of the carbon material and the electrolytic solution. By studying the nitrate anion reduction it is shown that the reduction over-voltage of stable compounds may be lowered by substituting a fast homogeneous reaction of solvated electrons with the initial substance for the hindered heterogeneous stage of the first electron transfer.

Pulse radiolysis study of the formation and the reactivity of baicalin radical anion, and in comparison with rutin, quercetin and acyrlate ester radical anions in ethanol

The reaction of solvated electrons with baicalin in N 2-saturated ethanol has been studied by pulse radiolysis. The results show that a solvated electron can add to baicalin and generate a baicalin radical anion with a maximum UV absorbance peak at 360 nm. Its molar extinction coefficient at this wavelength is 1.3×10 4 M −1 cm −1. The rate constant for the build-up of the baicalin radical anion is 1.3(±0.4)×10 10 M −1 s −1. Decay of the radical anion is induced by a proton transfer reaction and a recombination reaction, which involves a pseudo-first-order reaction with rate constant 2.6(±0.4)×10 3 s −1 and a second-order reaction with rate constant 1.3(±0.2)×10 9 M −1 s −1. The effect of acetaldehyde on the decay of the baicalin radical anion was also investigated. Electron transfer between the baicalin radical anion and acetaldehyde was not observed, probably due to the low rate of electron transfer between the baicalin radical anion and acetaldehyde. Reactivity of the rutin, quercetin, baicalin and ethyl acrylate radical anions are also compared.

Radiolysis of silver ion solutions in ethylene glycol: solvated electron and radical scavenging yields

The solvated electron yield in neat ethylene glycol (1,2-ethanediol), measured using pulse radiolysis, is G ( e solv - ) 10 ns =(1.7±0.2)×10 −7 mol J −1. The rate constant of the reaction of solvated electrons with silver cations is k ( e solv - + Ag + ) =(2.8±0.1)×10 9 dm 3 mol −1 s −1 and the absorption band maximum of Ag 0 is at 350 nm. The surface plasmon band of the silver clusters appears slowly at around 400 nm with a coalescence cascade rate constant of 2×10 6 dm 3 mol −1 s −1. The free silver ions do not scavenge ethylene glycol radicals. In contrast, the γ-radiolysis reduction yield of Ag + into clusters is dose-dependent, changing from G i(Ag n )=(2.5±0.5)×10 −7 mol J −1 at low dose to G max(Ag n )=(7.5±0.5)×10 −7 mol J −1 at higher doses, when clusters accumulate. Silver cations adsorbed on clusters are able to scavenge the ethylene glycol radicals, which also contribute to their reduction for a part of G rad=(5.8±0.5)×10 −7 mol J −1. Considering the different ways the reducing radicals can be produced, it is concluded that they originate from the electron–cation recombination and from the cation–ethylene glycol reaction, but that the dissociation of excited states is a negligible path. The formation mechanisms of the radicals and the rate constants in ethylene glycol are compared with those in water and methanol.

Glycosidic bond cleavage of thymidine by low-energy electrons.

Thymidine was exposed to low-energy electrons (LEE) as a thin solid film under a high vacuum. Nonvolatile radiation products, remaining on the irradiated surface, were analyzed by HPLC/UV and GC/MS. Here, we show that exposure of thymidine to 3-100 eV electrons gives thymine as a major product with a yield of 3.2 x 10-2 per electron (about one-third of the total decomposition of thymidine). The formation of thymine indicates that LEE induces cleavage of the glycosidic bond separating the base and sugar moieties, suggesting a nonionizing resonant process involving dissociative attachment (<15 eV). In contrast, this reaction is not very efficient by DNA base ionization and does not occur by the reaction of solvated electrons with DNA. These studies introduce a new mechanism of DNA damage involving the interaction of LEE.

Reactivity of OH[rad] and e−aq from electron beam irradiation of aqueous solutions of EDTA and aminopolycarboxylic acids

Electron beam irradiation of aqueous solutions of EDTA, EDDA NN′, NTA, IDA and Cu-EDTA was performed in the presence of scavengers for the hydroxyl radicals (methanol) or for the solvated electrons (hydrogen peroxide). Experiments showed that for each molecule, the G-value decreases as the radiation dose increases from 1 to 25kGy, and for EDTA, when the initial concentration decreases from 10 to 0.1mmoll−1. At pH 8 and for 5kGy, the G-values of NTA, IDA, EDTA and EDDA NN′ removal ascribed to OH radicals are, respectively, 0.06, 0.06, 0.15 and 0.20μmolJ−1, whereas for the solvated electrons the G-values were, respectively, 0.01, 0.01, 0.06 and 0.04μmolJ−1.The rate constants of hydroxyl radicals and solvated electrons were determined by comparison with one competitor. For each active species (hydroxyl radical or solvated electron), the reactivity is connected to the number of nitrogen atoms and acetate groups. The rate constants of OH radicals are above 1010 and 8.6×109lmol−1s−1 for EDDA NN′ and EDTA, respectively, 2.1×109lmol−1s−1 for IDA and 6.1×108lmol−1s−1 for NTA. The reactivity of solvated electrons is smaller and the rate constants are in the range 1.9×106–3.7×106lmol−1s−1 for NTA, IDA and EDDA NN′ and equal 1.4×107lmol−1s−1 for EDTA. The reactivity of the complex Cu-EDTA towards OH does not differ to a large extent from EDTA whereas with e−aq the reactivity of Cu-EDTA is better than EDTA since ke−/Cu-EDTA reaches 2.2×109lmol−1s−1.It follows that when both active entities (OH and e−aq) are involved in the electron beam irradiation process, the removal of free aminopolycarboxylic acids is mainly due to OH radicals. However, the complex Cu-EDTA is concerned by both e−aq and OH radicals.

Formation and Reaction of Br2•- Radicals in the Ionic Liquid Methyltributylammonium Bis(trifluoromethylsulfonyl)imide and in Other Solvents

Reaction of solvated electrons with BrCH2CH2Br produces Br- and •CH2CH2Br, which decomposes rapidly into CH2CH2 and Br•. Reaction of Br• with Br- forms Br2•-. The stability of Br2•- is much greater...

Electric field impact on solvated electron reactions: Trapping of randomly walking electron

The impact of an external electric field on electron seizure by neutral traps was studied within the Torrey model of a solvated electron random walk. The step length of the random motion, determined by the free diffusion of a temporarily escaped electron, increases with electric field strength, changing the reaction mechanism from a diffusional to a hopping one. The field dependence of the rate of the hopping reaction essentially differs from that obtained for diffusional trapping. Such a difference may serve for experimental discrimination between the hopping and diffusional mechanisms of this reaction.

An Advanced Tool for the Selection of Electrolyte Components for Rechargeable Lithium Batteries

The solid electrolyte interphase (SEI) plays a key role in lithium‐metal, lithium‐alloy, and lithium‐ion batteries. The SEI on both lithium and carbonaceous electrodes consists of many different materials including LiF, , lithium alkoxides, nonconductive polymers, and more. Close to the lithium or the SEI consists of the thermodynamically stable anions, such as , and halides. Close to the solution the SEI also contains partially reduced materials such as polyolefins, semicarbonates, etc. These materials form simultaneously and precipitate on the electrode as a mosaic of microphases. These phases may, under certain conditions, form separate layers, but in general it is more appropriate to treat them as heteropolymicrophases. The SEI composition and properties depend strongly on electrolyte composition and on other factors. Rapid formation of the SEI is important in all lithium batteries, especially in the case of lithium‐ion cells with graphite anodes. Hence SEI precursors must be selected from a group of materials that have high exchange current density (i0) for reduction. As it is difficult to measure i0 on solid electrodes and only limited data, if any, are available, it is suggested to use the data bank for the rate constant for the reduction of electrolyte components by hydrated electrons . We have demonstrated that the rate constants of the reactions of solvated electrons and electrolyte components and impurities correlate well with the formation voltage of SEI and with SEI composition. Thus, the rate constants (ke) for these reactions are proposed as a tool for the first screening of electrolyte components when a new electrolyte is designed.