Radical salt composition and method

Abstract

The present disclosure relates to radical salt compositions, methods of preparing such compositions, and methods of use in chemical reactions, particularly in the destruction and remediation of PFAS.

Description

[0001]3220-427902 PRF 70790-02 RADICAL SALT COMPOSITION AND METHOD RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 676,159, filed July 26, 2024, the entire disclosure of which is incorporated herein by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH This invention was made with government support under GM138133 awarded by the National Institutes of Health. The government has certain rights in the invention. BACKGROUND Perfluorinated organic compounds (PFC) and per- and polyfluoroalkyl substances (PFAS) are widely used anthropogenic chemicals. Because of the strength of the carbon– fluorine bond, PFAS are difficult to be degraded in conventional water treatment. Due to the potential harm for human health, the US-EPA set an advisory drinking water standard for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) of 70 μg L−1. PFC have a high persistence in the environment and especially long chain PFC such as PFOA and PFOS have the tendency for bioaccumulation. Perfluorinated compounds survive most of the conventional techniques in drinking- and wastewater treatment and were observed in finished drinking water in Germany, Switzerland, USA and other countries. In particular, treatment techniques based on the structural change of the target molecules such as ozonation or hydroxyl radical (OH•) based oxidation (advanced oxidation) fail due to the high chemical stability of these compounds. Sulfate radical anions ([SO4]•-) are currently being investigated for its uses as a remediator of PFAS, PFOA, and other short chain fluorinated alkyl compounds present in the environment. SO4• ─is a strong oxidizing agent with a reduction potential in the range of 2.5– 3.1 V. Due to extreme oxidation potential, SO4• ─has a capacity to oxidize organic pollutants to CO2and H2O. Additionally, SO4• ─has a half-life span of 30–40 μs, which is comparatively higher than•OH with a half-life span of 1 μs. A higher half-life span permits tremendous interaction and mass transfer between a pollutant and SO4• ─. These sulfate radicals can be generated in various ways such as UV-photolysis and reduction of peroxodisulfate (S2O82─) or peroxomonosulfate (HSO5─) by transition metals as well as thermolysis of S2O82─(T > 40 °C). Despite its potential for remediation, there is a current need to provide a facile method for the formation, and storage, of this highly reactive species. For example, if solubility 3220-427902 PRF 70790-02 equilibria can be overcome more quickly than radical lifetimes, extremely reactive radicals can be fossilized to be used as a reagent for future chemical reactions. SUMMARY In one aspect, the disclosure relates to a solid composition comprising a salt of a sulfate radical anion and a counter ion. In another aspect, the disclosure relates to a method of remediating a per- and / or polyfluoroalkyl substance (PFAS), the method comprising contacting the PFAS in an aqueous medium (e.g., a first aqueous medium) with a sulfate radical anion, thereby degrading the PFAS. In yet another aspect, the disclosure relates to a method of preparing a composition comprising a salt of a sulfate radical anion and a counter ion, the method comprising applying a potential at an electrode to a solution comprising a reactant and a counter ion in a solvent, thereby forming the composition comprising a salt of a sulfate radical anion and a counter ion. Additional embodiments, features, and advantages of the disclosure will be apparent from the following detailed description and through practice of the disclosure. The compounds of the present disclosure can be described as embodiments in any of the following enumerated clauses. It will be understood that any of the embodiments described herein can be used in connection with any other embodiments described herein to the extent that the embodiments do not contradict one another. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1A shows an experimental Schematic of the different types of electrochemical cell configurations with respect to the working electrode. The first configuration is the face-on view where the objective images the entire face of the electrode. Next, the profile view uses a side- on electrochemical cell to image the side of the electrode. The ITO working electrode forms the bottom of the cell for the ITO experimental view. The orange arrows represent the optical path of imaging using the inverted widefield microscopy. In all experiments, a 1 M KCl Ag / AgCl working electrode was used. A glassy carbon rod or a graphite rod (not depicted) was used as the counter electrode. FIG. 1B shows a reaction diagram of the solution phase reductive coreactant ECL reaction between the persulfate anion and [Ru(bpy)3]2+. The [Ru(Bpy)3]2+is reduced to [Ru(Bpy)3]+which then a portion of the population of the molecules can act as a strong reducing agent of [S2O8]2-to [SO4]•-and [SO4]2-. The generated [SO4]•-can act as a strong 3220-427902 PRF 70790-02 oxidizing agent to a [Ru(Bpy)3]+, which then may form the excited state: [Ru(Bpy)3]2+*, which then a portion of the excited state containing ions may undergo a radiative transition to emit a photon. FIG. 1C shows a reaction diagram of the reductive coreactant ECL reaction between the persulfate anion and [Ru(bpy)3]2+and the precipitation of [Ru(bpy)3][SO4]•during an applied potential, and the formation of the excited state [Ru(Bpy)3]2+*after the potential is stopped. FIG. 2A shows an absorption spectrum of 0.065 mM K2Ru(bpy)3([Ru(bpy)3]2+), 0.32 mM K2S2O8 ([S2O8]2-), and 0.64 mM KCl in 50 / 50 (v / v) water-Acetonitrile solution. FIG.2B shows a photoluminesce (PL) spectrum of the same system as in Fig.2A. The excitation was formed through shining a broad-spectrum LED light through a filter cube with an excitation wavelength window of 532-558 nm. FIG.2C shows an ECL emission spectrum as crystals nucleate along the surface of the electrode. λmax is present around 620 nm. FIG. 2D shows a representative potential step that was held at 0 V for 5 s, -1.65 V for 100 s, and then 0 V for another 130 s. An i-t curve is shown corresponding to the potential applied. FIG. 3A shows images of ECL microscopy performed in the face-on view with a 5X objective and an EMCCD camera. The ECL signal intensity becomes more heterogeneous with time, and as crystals start to nucleate and grow, the tips of the crystals show a marked increase in intensity. Scale bars are 250 μm. FIG. 3B shows images of ECL microscopy performed in a profile view with a 5X objective and a CMOS camera. The crystals grow to ca. 170 μm away from the electrode surface. Similar to the face-on view, the tips of the crystals have an increased ECL signal. Scale bars are 250 μm. FIG. 4A shows images of the dissolution of the [Ru(bpy)3][SO4]•crystals after the shutoff of the potentiostat (30 s of applied potential). Individual crystals can be seen shortening in length (dissolving) after the potentiostat ended. The scale bar is 500 μm. FIG.4B shows a graph of an afterglow ECL intensity-time trace after 100 s of applied potential. The initial spike at 100 s is the discharge from the potentiostat’s program ending and corresponding spike in ECL intensity. As the layers of crystals dissolve, more surface area is available to dissolve, thus increasing the output of ECL signal. This is concluded by the final layer of crystals starting to dissolve at 152 s resulting in a rapid decrease of signal. 3220-427902 PRF 70790-02 FIG.4C shows an image of the fluorescence of dried crystals. Shortly (ca.2 s) after the finishing of 50 s of applied potential, the electrochemical cell, composed with an ITO working electrode, solution was decanted and all electrodes were disconnected. The cell was then dried under continuous flow of nitrogen gas. After it finished drying, solid-state fluorescence micrographs were acquired using the Y3 filter. FIG.5A shows an image of the addition of Acetonitrile (ACN) causing a precipitate to form in the 10 mM [Ru(bpy)3]2+, and 100 mM K2SO4 solution. FIG.5B shows an image of the precipitate from FIG.5A after drying. FIG. 5C shows an image of the electrode transfer experiment from the original vial containing 10 mM [Ru(bpy)3]2+, and 50 mM K2S2O8, to a vial containing 10 mM [Ru(bpy)3]2+. The electrode was unclipped before transferring. The electroless afterglow electrochemiluminescence is present after the electrode transfer. FIG. 5D shows a graph of the electroless afterglow ECL with (labeled B) and without (labeled A) presence of a scavenger (hexacyanoferrate (II)) on a glassy carbon macroelectrode. The applied potential was shutoff at 210 s (vertical line). With ferrocyanide present, the signal decreases rapidly compared to the trial without the presence of a scavenger. This is in the inverted configuration; thus, the afterglow is short-lived due to the crystals falling away from the electrode. FIG. 5E shows an image of a pile of crystals collected at the bottom of a scintillation vial after 60 s of applied potential with a 2-electrode system. The photograph was acquired at 33 s after the electrodes were removed from solution and lasted ca.10 minutes. FIG. 6A shows an overlaid ESR spectra of K2S2O8 (solid line) Ru(bpy)3Cl2•6H2O (small dash), and the [Ru(bpy)3][SO4]•crystals (dash). The spectra were normalized for the amount of sample loaded into the ESR tubes, as well as the amount of cycles. FIG.6B shows an ESR spectrum of K2S2O8. The small signal may be due to the photo- decomposition due to the ESR tubes being out in the light. FIG. 6C shows an ESR spectrum of Ru(bpy)3Cl2•6H2O. A small portion of the Ruthenium may be in a Ru(I / III) state from impurities; thus a small signal is shown. FIG.6D shows an ESR spectrum of the [Ru(bpy)3][SO4]•crystals. DETAILED DESCRIPTION Before the present disclosure is further described, it is to be understood that this disclosure is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing 3220-427902 PRF 70790-02 particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended clauses. For the sake of brevity, the disclosures of the publications cited in this specification, including patents, are herein incorporated by reference. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. All patents, applications, published applications and other publications referred to herein are incorporated by reference in their entireties. If a definition set forth in this section is contrary to or otherwise inconsistent with a definition set forth in a patent, application, or other publication that is herein incorporated by reference, the definition set forth in this section prevails over the definition incorporated herein by reference. As used herein and in the appended clauses, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the clauses may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of clause elements, or use of a “negative” limitation. As used herein, the terms “including,” “containing,” and “comprising” are used in their open, non-limiting sense. The term “about” as used herein means greater or lesser than the value or range of values stated by 10 percent, but is not intended to designate any value or range of values to only this broader definition. Each value or range of values preceded by the term "about" is also intended to encompass the embodiment of the stated absolute value or range of values. To provide a more concise description, some of the quantitative expressions given herein are not qualified with the term “about.” It is understood that, whether the term “about” is used explicitly or not, every quantity given herein is meant to refer to the actual given value, and it is also meant to refer to the approximation (e.g., 10%, 5%, or 1%) to such given value that would reasonably be inferred based on the ordinary skill in the art, including equivalents and approximations due to the experimental and / or measurement conditions for such given value. Whenever a yield is given as a percentage, such yield refers to a mass of the entity for which the yield is given with respect to the maximum amount of the same entity that could be obtained under the particular stoichiometric conditions. Concentrations that are given as percentages refer to mass ratios, unless indicated differently. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure 3220-427902 PRF 70790-02 belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. Except as otherwise noted, the methods and techniques of the present embodiments are generally performed according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout the present specification. See, e.g., Loudon, Organic Chemistry, Fourth Edition, New York: Oxford University Press, 2002, pp.360-361, 1084-1085; Smith and March, March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, Fifth Edition, Wiley-Interscience, 2001. Chemical nomenclature for compounds described herein has generally been derived using the commercially-available ACD / Name 2014 (ACD / Labs) or ChemBioDraw Ultra 13.0 (Perkin Elmer). As used herein and in connection with chemical structures depicting the various embodiments described herein, “*”, “**”, and “ ”, each represent a point of covalent attachment of the chemical group or chemical structure in which the identifier is shown to an adjacent chemical group or chemical structure. For example, in a hypothetical chemical structure A-B, where A and B are joined by a covalent bond, in some embodiments, the portion of A-B defined by the group or chemical structure A can be represented by , , or , where each of “-*”, “-**”, and “ ” represents a bond to A and the point of covalent bond attachment to B. in some embodiments, the portion of A-B defined by the group or chemical structure B can be represented by , , or , where each of “-*”, “-**”, and “ ” represents a bond to B and the point of covalent bond attachment to A. It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination. All combinations of the embodiments pertaining to the chemical groups represented by the variables are specifically embraced by the present disclosure and are disclosed herein just as if each and every combination was individually and explicitly disclosed, to the extent that such combinations embrace compounds that are stable compounds (i.e., compounds that can be isolated, characterized, and tested for biological activity). In 3220-427902 PRF 70790-02 addition, all subcombinations of the chemical groups listed in the embodiments describing such variables are also specifically embraced by the present disclosure and are disclosed herein just as if each and every such sub-combination of chemical groups was individually and explicitly disclosed herein. DEFINITIONS Unless otherwise defined herein, scientific and technical terms used in this application shall have the meanings that are commonly understood by those of ordinary skill in the art. Generally, nomenclature used in connection with, and techniques of, chemistry, cell and tissue culture, molecular biology, cell and cancer biology, neurobiology, neurochemistry, virology, immunology, microbiology, pharmacology, genetics and protein and nucleic acid chemistry, described herein, are those well known and commonly used in the art. The methods and techniques of the present disclosure are generally performed, unless otherwise indicated, according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout this specification. See, e.g., “Principles of Neural Science”, McGraw-Hill Medical, New York, N.Y. (2000); Motulsky, “Intuitive Biostatistics”, Oxford University Press, Inc. (1995); Lodish et al., “Molecular Cell Biology, 4th ed.”, W. H. Freeman & Co., New York (2000); Griffiths et al., “Introduction to Genetic Analysis, 7th ed.”, W. H. Freeman & Co., N.Y. (1999); and Gilbert et al., “Developmental Biology, 6th ed.”, Sinauer Associates, Inc., Sunderland, Mass. (2000). Chemistry terms used herein, unless otherwise defined herein, are used according to conventional usage in the art, as exemplified by “The McGraw-Hill Dictionary of Chemical Terms”, Parker S., Ed., McGraw-Hill, San Francisco, Calif. (1985). All of the above, and any other publications, patents and published patent applications referred to in this application are specifically incorporated by reference herein. In case of conflict, the present specification, including its specific definitions, will control. As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may occur or may not occur, and that the description includes instances where the event or circumstance occurs as well as instances in which it does not. For example, “optionally substituted alkyl” refers to the alkyl may be substituted as well as where the alkyl is not substituted. The term “Log of solubility”, “LogS” or “logS” as used herein is used in the art to quantify the aqueous solubility of a compound. The aqueous solubility of a compound 3220-427902 PRF 70790-02 significantly affects its absorption and distribution characteristics. A low solubility often goes along with a poor absorption. LogS value is a unit stripped logarithm (base 10) of the solubility measured in mol / liter. The terms “amine” and “amino” are art-recognized and refer to both unsubstituted and substituted amines and salts thereof, e.g., a moiety that can be represented by the formula – N(R1)(R2) or –N+(R1)(R2)(R3), wherein R1, R2, and R3, each independently represent a hydrogen or a hydrocarbyl group. The term “hydrocarbyl”, as used herein, refers to a group that is bonded through a carbon atom that does not include a ═O or ═S, and typically has at least one carbon-hydrogen bond and a primarily carbon backbone, but may optionally include heteroatoms. Hydrocarbyl groups include, but are not limited to, methyl, ethyl, propyl (e.g., n-propyl, isopropyl), and combinations thereof. The term “peroxide” is art-recognized and refers to the group represented a compound containing two oxygen atoms bonded together or as the anion O22−. The term “sulfate” is art-recognized and refers to the group —OSO3H. The term “sulfate anion,” as used herein, refers to the group represented by the general formula SO42-. The term “sulfate radical anion,” as used herein, refers to the group represented by the general formula SO4•-. The term “persulfate” is art-recognized and refers to the group represented by the general formula . An example of a persulfate is persulfate anion (S2O8)2-. The term “salt” is art recognized and refers to a compound including an ion and a counter ion bound by ionic bonds. It will be understood that the chemical entities described herein can exist as a salt of an ion and a counter ion. Salts are typically formed when an acid or a sufficiently acidic group reacts with a base or a sufficiently basic group, resulting in the formation of a salt and water through a chemical reaction called neutralization. Examples of salts include sulfates, pyrosulfates, bisulfates, sulfites, bisulfites, phosphates, monohydrogen- phosphates, dihydrogenphosphates, metaphosphates, pyrophosphates, chlorides, bromides, iodides, acetates, propionates, decanoates, caprylates, acrylates, formates, isobutyrates, caproates, heptanoates, propiolates, oxalates, malonates, succinates, suberates, sebacates, fumarates, maleates, butyne-1,4-dioates, hexyne-1,6-dioates, benzoates, chlorobenzoates, methylbenzoates, dinitrobenzoates, hydroxybenzoates, methoxybenzoates, phthalates, 3220-427902 PRF 70790-02 sulfonates, methylsulfonates, propylsulfonates, besylates, xylenesulfonates, naphthalene-1- sulfonates, naphthalene-2-sulfonates, phenylacetates, phenylpropionates, phenylbutyrates, citrates, lactates, γ-hydroxybutyrates, glycolates, tartrates, and mandelates. The term “counter ion” is art-recognized and refers to an oppositely charged ion that accompanies an ionic species (i.e., “ion”) in order to maintain electric neutrality. A counter ion may represent an anion (negatively charged ion) or a cation (positively charged ion). In certain embodiments, an ion or counter ion may be a radical anion (e.g., [SO4]•-) or a radical cation. Illustratively, an anion represented by the general formula “Xn−” (e.g., a persulfate anion, S2O82−) or “X•n−” (e.g., a sulfate radical anion, SO4•−) may exist as a complex or salt with a suitable counter ion including, but not limited to, an alkali metal, an alkaline-earth metal, or a transition metal, such as lithium (Li+), sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), and the like. Illustratively, a persulfate anion (S 2- 2O8 ) may exist with potassium counter cations (K+) as a potassium persulfate salt (K2S2O8), a cation comprising ruthenium (e.g., [Ru(bpy)3]+) may exist with a sulfate radical counter anion (SO4•−) as a tris(bipyridine)ruthenium(II) sulfate radical salt ([Ru(bpy)3][SO4]•), and a cation comprising ruthenium (e.g., [Ru(bpy)3]2+) may exist with chloride counter ions (Cl-) as a tris(bipyridine)ruthenium(II) chloride salt (Ru(bpy)3Cl2). The term “radical ion,” as used herein, refers to a free radical species that carries a charge. A radical anion carries a negative charge, and a radical cation carries a positive charge. In some embodiments, salts of the radical ions (i.e., radical salts) may be isolated as solids or used in situ. The terms “reactant” and “coreactant,” as used herein, refer to a compound that is capable of being oxidized or reduced to form a strongly oxidizing or reducing species, for example a radical. Examples of reactants include tri-n-propylamine, oxalate anion, persulfate anion, and benzoyl peroxide. The term “in situ,” as used herein, refers to performing an experiment in the same vessel, at the same site, or at the same location as an initial reaction. For example, in situ electrochemical experiments are performed under operating conditions of the electrochemical cell (i.e., under potential control). Illustratively, it will be understood that the phrase “forming a sulfate radical anion in situ” or “a sulfate radical anion is formed in situ” with respect to a method including a step of contacting a PFAS with a sulfate radical anion may refer to forming the sulfate radical anion in the same vessel, at the same site, or at the same location as the contacting. 3220-427902 PRF 70790-02 The term “ex situ,” as used herein, refers to performing an experiment in a different (outside of) vessel, at a different site, or at a different location than an initial reaction. For example, ex situ electrochemical experiments are performed under the absence of potential control. Illustratively, it will be understood that the phrase “forming a sulfate radical anion ex situ” or “a sulfate radical anion is formed ex situ” with respect to a method including a step of contacting a PFAS with a sulfate radical anion may refer to forming the sulfate radical anion in a different vessel, at a different site, or at a different location as the contacting. The term “insoluble,” as used herein, refers to a substance that is incapable of being dissolved in a liquid, or soluble only with difficulty or to a slight degree. In some embodiments, an insoluble substance provides a concentration of less than 0.1 M in solution. The term “aqueous insoluble,” as used herein, refers to a substance that is incapable of being dissolved in a water, or soluble only with difficulty or to a slight degree. In some embodiments, an insoluble substance provides a concentration of less than 0.1 M in water. The terms “precipitate” and “solid precipitate,” as used interchangeably herein, refer to an insoluble solid that emerges from a liquid solution. The term “precipitation,” as used herein, refers to the emergence of the insoluble solid from solution. For example, precipitates can form when two soluble salts react in solution to form one or more insoluble products. The term “crystal,” as used herein, refers to a precipitate and / or an insoluble salt. For example, a crystal (e.g., [Ru(byp)3][SO4]·) may include a reduced luminophore and a radical coreactant. REPRESENTATIVE EMBODIMENTS A method to synthesize reactive radical salts, effectively freezing radicals in space and time is provided herein. This is accomplished through the electroprecipitation of sulfate radical anion SO4.-and a counter ion during the simultaneous electro-reduction of persulfate anion. An electrode generates a concentration profile exceeding the solubility of sulfate radical anion, promoting crystal formation. The methods described herein suggest an elegant new chemical tenet: extremely reactive radicals can be bottled-up to be used as future reagents so long as the precipitation rate exceeds the radical lifetime. In certain embodiments, the methods described herein may be useful for applications in PFAS remediation and destruction. In some embodiments, the disclosure relates to a solid composition comprising a salt of a sulfate radical anion and a counter ion. 3220-427902 PRF 70790-02 In some embodiments, the salt is a solid. In some embodiments, the salt is a precipitate (e.g., a solid precipitate). In some embodiments, the counter ion comprises a cation selected from the group consisting of an alkali metal (e.g., Li, Na, K, Rb, Cs, or Fr), an alkaline-earth metal (e.g., Be, Mg, Ca, Sr, Ba, or Ra), or a transition metal (e.g., Fe or Ru). In some embodiments, the counter ion is calcium or magnesium. In some embodiments, the composition comprises the formula [M] • x[SO4]y, where M comprises a counter ion selected from the group consisting of an alkali metal (e.g., Li, Na, K, Rb, Cs, or Fr), an alkaline-earth metal (e.g., Be, Mg, Ca, Sr, Ba, or Ra), or a transition metal (e.g., Mn, Fe, Co, Ni, Cu, Ru, Rh, Pb, or Ag), and each x and y is independently an integer of 1, 2, or 3. In some embodiments, the composition comprises the formula [Ca][SO • 4]2 or [Mg][SO ]• 2. In some embodiments, th • 4 e salt comprises the formula [Ca][SO4]2. In some embodiments, the disclosure relates to a method of remediating a per- and / or polyfluoroalkyl substance (PFAS), the method comprising contacting the PFAS in an aqueous medium (e.g., a first aqueous medium) with a sulfate radical anion, thereby degrading the PFAS. In some embodiments, the aqueous medium (e.g., a first aqueous medium) is water. In some embodiments, the aqueous medium is water or a mixture (e.g., a 50 / 50 v / v) of water and a water-miscible solvent (e.g., acetonitrile, acetone, tetrahydrofuran (THF), dimelthylsulfoxide (DMSO), and ethyl acetate). In some embodiments, the method of remediating a PFAS comprises providing the sulfate radical anion to an aqueous medium (e.g., a first aqueous medium) comprising PFAS. In some embodiments, the method of remediating a PFAS comprises providing a sulfate radical anion to an aqueous medium comprising PFAS, and contacting the PFAS with the sulfate radical anion to degrade the PFAS. In some embodiments, the method of remediating a PFAS comprises forming a sulfate radical anion in the aqueous medium comprising PFAS (e.g., the first aqueous medium) (i.e., in situ). In some embodiments, the method of remediating a PFAS forms a sulfate radical anion in an aqueous medium (e.g., the first aqueous medium) comprising PFAS, and contacting the PFAS with the sulfate radical anion. In some embodiments, the method of remediating a PFAS comprises forming a sulfate radical anion in an aqueous medium (e.g., the first aqueous medium) comprising PFAS, and contacting the PFAS with the sulfate radical anion to degrade the PFAS. 3220-427902 PRF 70790-02 In some embodiments, the method of remediating a PFAS comprises forming the sulfate radical anion in a second aqueous medium (e.g., ex situ). In some embodiments, the second aqueous medium is different than the aqueous medium (e.g., the first aqueous medium). For example, the second aqueous medium may not comprise PFAS. In some embodiments, the second aqueous medium is water. In some embodiments, the second aqueous medium is water or a mixture (e.g., a 50 / 50 v / v) of water and a water-miscible solvent (e.g., acetonitrile, acetone, tetrahydrofuran (THF), dimelthylsulfoxide (DMSO), and ethyl acetate). In some embodiments, the second aqueous medium is a mixture (e.g., a 50 / 50 v / v) of water and acetonitrile. In some embodiments, the method of remediating a PFAS comprises adding a sulfate radical anion to an aqueous medium (e.g., the first aqueous medium) comprising PFAS. In some embodiments, the method of remediating a PFAS comprises forming a sulfate radical anion in a second aqueous medium, adding the a sulfate radical anion to a first aqueous medium comprising PFAS, and contacting the PFAS with the sulfate radical anion. In some embodiments, the method of remediating a PFAS comprises forming a sulfate radical anion in a second aqueous medium, adding the sulfate radical anion to a first aqueous medium comprising PFAS, and contacting the PFAS with the sulfate radical anion to degrade the PFAS. In some embodiments, the method of remediating a PFAS comprises precipitating a salt comprising the sulfate radical anion and a counter ion in the second aqueous medium. In some embodiments, the method of remediating a PFAS comprises precipitating a salt comprising the sulfate radical anion and a counter ion in the second aqueous medium, and adding the sulfate radical anion to the aqueous medium (e.g., the first aqueous medium). In some embodiments, the method of remediating a PFAS comprises dissolving the salt comprising a sulfate radical anion and a counter ion. In some embodiments, the dissolving releases the sulfate radical anion into the aqueous medium (e.g., the first aqueous medium). In some embodiments, the method of remediating a PFAS comprises precipitating a salt comprising the sulfate radical anion and a counter ion in the second aqueous medium, and adding the sulfate radical anion to the aqueous medium (e.g., the first aqueous medium) to dissolve the salt and to release the sulfate radical anion into the aqueous medium (e.g., the first aqueous medium). In some embodiments, the method of remediating a PFAS comprises precipitating a salt comprising the sulfate radical anion and a counter ion in a second aqueous medium, adding the sulfate radical anion to a first aqueous medium comprising PFAS, and contacting the PFAS with the sulfate radical anion to degrade the PFAS. In some embodiments, the method of 3220-427902 PRF 70790-02 remediating a PFAS comprises precipitating a salt comprising the sulfate radical anion and a counter ion in a second aqueous medium, adding the sulfate radical anion to a first aqueous medium comprising PFAS to dissolve the salt and release the sulfate radical anion into the first aqueous medium, and contacting the PFAS with the sulfate radical anion to degrade the PFAS. In some embodiments, the method of remediating a PFAS comprises oxidizing the PFAS. In some embodiments, the method of remediating a PFAS comprises oxidizing the PFAS to degrade the PFAS. In some embodiments, the method of remediating a PFAS comprises contacting PFAS with a sulfate radical anion and a counter ion, and oxidizing the PFAS. In some embodiments, the method of remediating a PFAS comprises contacting PFAS with a sulfate radical anion and a counter ion, and oxidizing the PFAS to degrade the PFAS. In some embodiments, the method of remediating a PFAS comprises providing a sulfate radical anion to an aqueous medium comprising PFAS, contacting the PFAS with the sulfate radical anion, and oxidizing the PFAS. In some embodiments, the method of remediating a PFAS comprises providing a sulfate radical anion to an aqueous medium comprising PFAS, contacting the PFAS with the sulfate radical anion, and oxidizing the PFAS to degrade the PFAS. In some embodiments, the disclosure relates to a method of preparing a composition comprising salt of a sulfate radical anion and a counter ion, the method comprising applying a potential at an electrode to a solution comprising a reactant and a counter ion in a solvent. In some embodiments, the composition comprising a salt of a sulfate radical anion and a counter ion is a solid composition. In some embodiments, the disclosure relates to a method of preparing a composition comprising salt a sulfate radical anion and a counter ion, the method comprising applying a potential at an electrode to a solution comprising a reactant and a counter ion in a solvent, thereby forming the composition comprising a salt of a sulfate radical anion and a counter ion. In some embodiments, the method of preparing a composition includes a step of applying a potential to a solution comprising a reactant and a counter ion in a solvent. In some embodiments, the solution comprises a reactant, a counter ion, and an electrolyte (e.g., KCl) in a solvent. In some embodiments, the method includes a step of applying a potential at an electrode to a solution comprising a reactant and a counter ion. In some embodiments, the method includes a step of applying a potential at an electrode to a solution comprising a reactant and a counter ion to form a composition comprising a salt of a sulfate radical anion and a counter ion. In some embodiments, the method includes a step of applying a potential at an 3220-427902 PRF 70790-02 electrode to a solution comprising a reactant and a counter ion to form a composition comprising a salt of a sulfate radical anion and a counter ion on a surface of the electrode. In some embodiments, the method of preparing a composition includes reducing the reactant to provide the sulfate radical anion. In some embodiments, the method includes a step of applying a potential at an electrode to a solution comprising a reactant and a counter ion to reduce the reactant to provide the sulfate radical anion. In some embodiments, the method of preparing a composition includes nucleating the sulfate radical anion and the counter ion to form the salt on a surface of the electrode.. In some embodiments, the method includes a step of applying a potential at an electrode to a solution comprising a reactant and a counter ion to reduce the reactant to provide the sulfate radical anion and to nucleate the sulfate radical anion and the counter ion. In some embodiments, the method includes a step of applying a potential at an electrode to a solution comprising a reactant and a counter ion to reduce the reactant to provide the sulfate radical anion and to nucleate the sulfate radical anion and the counter ion to form a salt on a surface of the electrode. In some embodiments, the solvent is water, acetonitrile, acetone, tetrahydrofuran (THF), dimelthylsulfoxide (DMSO), ethyl acetate, ether, or any combination thereof. In certain embodiments, the solvent is water or a mixture (e.g., a 50 / 50 v / v) of water and a water-miscible solvent (e.g., acetonitrile, acetone, tetrahydrofuran (THF), dimelthylsulfoxide (DMSO), and ethyl acetate). In some embodiments, the solvent is a mixture (e.g., a 50 / 50 v / v) of water and acetonitrile. In some embodiments, a 50 / 50 v / v water-acetonitrile mixture may be advantageous in increasing the solubility of the persulfate anion and decreasing the quenching ability of persulfate. For example, the solubility of persulfate anion in water is around 60 mM; however, the persulfate anion readily complexes and forms a precipitate in the presence of Ru(bpy)32+at around ca.10-20 mM in water. In some embodiments, the reactant is selected from the group consisting of tri-n- propylamine, oxalate anion, persulfate anion, benzoyl peroxide, and any combination thereof. In certain preferred embodiments, the reactant is a persulfate anion (S2O82-). In some embodiments, the persulfate anion (S2O82-) is provided by potassium persulfate salt (K2S2O8). In some embodiments, the solution has a molar ratio of the counter ion to the reactant of about 1:1 to about 1:15. For example, the solution may have a molar ratio of the counter ion to the reactant of about 1:2 to about 1:10, or a molar ratio of the counter ion to the reactant of about 1:4 to about 1:6. In certain embodiments, the solution has a molar ratio of the counter ion to the reactant of about 1:5. 3220-427902 PRF 70790-02 In some embodiments, the solution has a counter ion concentration of about 1 mM to about 50 mM. For example, the solution may have a counter ion concentration of about 1 mM to about 20 mM. In certain embodiments, the solution has a counter ion concentration of about 10 mM. In some embodiments, the solution has a reactant concentration of about 1 mM to about 100 mM. For example, the solution may have a reactant concentration of about 20 mM to about 100 mM. In certain embodiments, the solution has a reactant concentration of about 50 mM. In some embodiments, the solution has an electrolyte concentration of about 1 mM to about 500 mM. For example, the solution may have an electrolyte concentration of about 50 mM to about 250 mM. In certain embodiments, the solution has a reactant concentration of about 100 mM. In some embodiments, the potential (i.e., voltage) applied to the solution is about -1.2 V to about -2.0 V. In some embodiments, the potential (i.e., voltage) applied to the solution is about -1.4 V to about -1.8 V. In some embodiments, the voltage is about -1.6 V. In some embodiments, the potential (i.e., voltage) is applied to the solution for about 1 second to about 500 seconds. For example, the potential (i.e., voltage) is applied to the solution for about 1 seconds to about 400 seconds, about 10 seconds to about 250 seconds, about 60 seconds to about 250 seconds, about 10 seconds to about 120 seconds, or for about 30 seconds to about 100 seconds. In some embodiments, the potential (i.e., voltage) is applied to the solution for about 30 seconds. In some embodiments, the potential (i.e., voltage) is applied to the solution for about 100 seconds. In some embodiments, the potential (i.e., voltage) is applied to the solution for about 210 seconds. In some embodiments, the method of preparing a composition includes reducing a reactant to provide a sulfate radical anion. In certain preferred embodiments, the method includes reducing a reactant (e.g., [S2O8]2-) to provide a the sulfate radical anion (e.g., [SO4]•-). In some embodiments, the high sulfate and sulfate radical concentration profile found at the surface of the electrode, when a potential is applied, causes the nucleation and growth of the crystal (i.e., salt) structures through electroprecipitation. In some embodiments, the method of preparing a composition includes nucleating the sulfate radical anion and the counter ion. In some embodiments, the method includes nucleating the sulfate radical anion and the counter ion to form the composition comprising a salt of a sulfate radical anion and a counter ion on the surface of the electrode. In some embodiments, the composition comprising a salt of a sulfate radical anion and a counter ion is a solid 3220-427902 PRF 70790-02 precipitate. For example, the electrode may generate a concentration profile exceeding the solubility of a sulfate radical anion and a counter ion, promoting nucleation and salt formation. In some embodiments, the method of preparing a composition includes forming a sulfate radical anion on the surface of the electrode (i.e., the sulfate radical anion forms on the surface of the electrode). In some embodiments, the method includes forming a composition comprising a salt of a sulfate radical anion and a counter ion on the surface of the electrode (i.e., the salt forms on the surface of the electrode). In some embodiments, the salt extends perpendicularly (i.e., grows outward) from the surface of the electrode. In some embodiments, the salt extends greater than about 10 µm from the surface of the electrode (i.e., the linear perpendicular distance between the interface of the surface of the electrode and the salt, and the terminal end of the salt). For example, the salt may extend greater than about 25 µm, greater than about 50 µm, greater than about 75 µm, greater than about 100 µm, greater than about 125 µm, greater than about 150 µm, between about 10 µm and about 200 µm, between about 25 µm and about 200 µm, between about 50 µm and about 200 µm, between about 100 µm and about 200 µm, or between about 150 µm and about 200 µm from the surface of the electrode. In some embodiments, the salt extends perpendicularly (i.e., grows outward) from the surface of the electrode at a particular rate defined by measurement of a length per second of applied potential. In some embodiments, the salt extends from the surface of the electrode at a rate of greater than about 0.1 µm per second (µm / s) of applied potential. For example, the salt grows at a rate of greater than about 0.1 µm / s, greater than about 0.5 µm / s, greater than about 1 µm / s, greater than about 2 µm / s, greater than about 3 µm / s, between about 0.1 µm / s and about 10 µm / s, between about 0.5 µm / s and about 5 µm / s, between about 0.5 µm / s and about 5 µm / s, or between about 1 µm / s and about 5 µm / s . In some embodiments, the potential is provided by an electrode. In some embodiments, potential is applied at an electrode. The electrode may include any suitable conductive material. In some embodiments, the electrode is selected from the group consisting of a working electrode (e.g., a glassy carbon rod, a graphite rod, an Indium Tin Oxide (ITO) electrode), a counter electrode (e.g., a glassy carbon rod, a graphite rod), a reference electrode (e.g., an Ag / AgCl electrode in a salt bridge), and any combination thereof. In some embodiments, the electrode includes a working electrode (e.g., a glassy carbon rod, a graphite rod,, an Indium Tin Oxide (ITO) electrode), a counter electrode (e.g., a glassy carbon rod, a graphite rod), and a reference electrode (e.g., an Ag / AgCl electrode in a salt bridge). In some embodiments, the electrode includes a glassy carbon rod, a second glassy carbon rod, and an 3220-427902 PRF 70790-02 Ag / AgCl electrode in a salt bridge. In some embodiments, the electrode includes an Indium Tin Oxide (ITO) electrode, a graphite rod, and an Ag / AgCl electrode in a salt bridge. In some embodiments, the electrode includes a graphite rod, and a second graphite rod. In some embodiments, the sulfate radical anion of the composition comprising a salt of a sulfate radical anion and a counter ion has a lifetime of greater than about 0.1 second. For example, the sulfate radical anion may have a lifetime of greater than about 1 second, greater than about 5 seconds, greater than about 10 seconds, greater than about 15 seconds, greater than about 30 seconds, greater than about 1 minute, greater than about 5 minutes, greater than about 10 minutes, greater than about 15 minutes, or greater than about 30 minutes. In some embodiments, the sulfate radical anion may have a lifetime of about 1 second to about 5 minutes, about 1 second to about 10 minutes, about 1 second to about 15 minutes, or about 1 second to about 30 minutes. In some embodiments, the method of preparing a composition includes drying the composition comprising a salt of a sulfate radical anion and a counter ion. In some embodiments, the method of preparing a composition includes storing the composition comprising a salt of a sulfate radical anion and a counter ion. In certain embodiments, a remediation method for PFAS uses composition described herein. In certain embodiments, the composition according to the present disclosure relates to a salt including a sulfate radical anion and a counter ion provided by an electroprecipitation reaction. In some embodiments, the electroprecipitation is the result of kinetics of nucleation and growth that are sufficiently faster than that of the radical lifetime so the sulfate radical anion co-precipitates with a cation. Additional Embodiments 1. A solid composition comprising a salt of a sulfate radical anion and a counter ion. 2. The composition of embodiment 1, wherein the salt is a solid precipitate. 3. The composition of embodiment 1 or 2, wherein the counter ion comprises a cation selected from the group consisting of an alkali metal an alkaline-earth metal, or a transition metal. 4. The composition of any one of the preceding embodiments, wherein the salt comprises the formula [Ca][SO4]•2. 5. A method of remediating a per- and / or polyfluoroalkyl substance (PFAS), the method comprising: 3220-427902 PRF 70790-02 contacting the PFAS in an aqueous medium (e.g., a first aqueous medium) with a sulfate radical anion, thereby degrading the PFAS. 6. The method of embodiment 5, further comprising: providing the sulfate radical anion to the aqueous medium (e.g., the first aqueous medium) comprising the PFAS. 7. The method of embodiment 6, wherein the step of providing comprises: forming the sulfate radical anion in the aqueous medium (e.g., the first aqueous medium) (i.e., in situ). 8. The method of embodiment 6, wherein the step of providing comprises: forming the sulfate radical anion in a second aqueous medium (e.g., ex situ), wherein the second aqueous medium is different than the aqueous medium (e.g., the first aqueous medium), and adding the sulfate radical anion to the aqueous medium (e.g., the first aqueous medium). 9. The method of embodiment 8, wherein the step of forming precipitates a salt comprising the sulfate radical anion and a counter ion in the second aqueous medium. 10. The method of embodiment 9, wherein the step of adding dissolves the salt and releases the sulfate radical anion into the aqueous medium (e.g., the first aqueous medium). 11. The method of embodiment 9 or 10, wherein the salt is a solid precipitate. 12. The method of any one of embodiments 9 to 11, wherein the counter ion comprises a cation selected from the group consisting of an alkali metal an alkaline-earth metal, or a transition metal. 13. The method of any one of embodiments 9 to 12, wherein the salt comprises the formula [Ca][SO4]•2. 14. The method of any one of embodiments 5 to 13, wherein the step of contacting oxidizes the PFAS. 15. A method of preparing a composition according to any one of embodiments 1 to 4, the method comprising: applying a potential at an electrode to a solution comprising a reactant and a counter ion in a solvent, thereby forming the composition comprising a salt of a sulfate radical anion and a counter ion. 3220-427902 PRF 70790-02 16. The method of embodiment 15, wherein the reactant is selected from the group consisting of tri-n-propylamine, oxalate anion, persulfate anion ([S2O8]2-), benzoyl peroxide, and any combination thereof; preferably the reactant is persulfate anion. 17. The method of embodiment 15 or 16, wherein the solution has a molar ratio of the counter ion to the reactant of about 1:1 to about 1:15, preferably about 1:2 to about 1:10, more preferably about 1:4 to about 1:6. 18. The method of any one of embodiments 15 to 17, wherein the solution has a concentration of the counter ion of about 1 mM to about 50 mM, preferably about 1 mM to about 20 mM, and a concentration of the reactant of about 1 mM to about 100 mM, preferably about 20 mM to about 100 mM. 19. The method of any one of embodiments 15 to 18, wherein the electrode is selected from the group consisting of a working electrode (e.g., a glassy carbon rod, a graphite rod, an Indium Tin Oxide (ITO) electrode), a counter electrode (e.g., a glassy carbon rod, a graphite rod), a reference electrode (e.g., an Ag / AgCl electrode in a salt bridge), and any combination thereof. 20. The method of any one of embodiments 15 to 19, wherein the step of applying reduces the reactant to provide the sulfate radical anion. 21. The method of any one of embodiments 15 to 20, wherein the step of applying nucleates the sulfate radical anion and the counter ion to form the salt on a surface of the electrode. EXAMPLES The following examples are offered to illustrate but not to limit the disclosure. Materials and Methods Afterglow Electrochemiluminescence for Tris(bipyridine) ruthenium (II) using the persulfate anion coreactant to form crystals is outlined and detailed herein. Potassium persulfate (99%), Potassium sulfate (99%), Calcium Chloride dihydrate (99%), and Potassium ferrocyanide trihydrate (99%) were purchased from Sigma-Aldrich. Potassium Chloride (99%), and Acetonitrile (99.9%) were purchased from Fisher Chemical. Tris(bipyridine)ruthenium(II) chloride hexahydrate ([Ru(bpy)3][Cl2]•6H2O, 98%) ([Ru(bpy)3]2+) was purchased from Acros Organics and was kept under Nitrogen in a desiccator. All water used was ultrapure water (>18.20 MΩ·cm, Thermo Scientific). All chemicals were used without further purification steps, unless noted otherwise. 3220-427902 PRF 70790-02 Solutions composed of 10 mM [Ru(bpy)3]2+, 50 mM K2S2O8, 100 mM KCl were prepared in 5 mL of 50 / 50 (v / v) Acetonitrile-Water solution in a 20 mL scintillation vial (ThermoFisher, USA). The solution was wrapped in aluminum foil and sonicated to fully dissolve. A Leica DMi8 inverted optical microscope (Leica Microsystems, Germany) was used to conduct microscopy experiments. The light source equipped is a pE-300lite light source (CoolLED, United Kingdom). The objective used was 5x with a numerical aperture of 0.12. An EMCCD iXon 897 camera (Andor Technology Ltd., Belfast, UK) was used with a 10 ms exposure time. The 10 MHz quality mode, a 4.22 μs shift speed and a temperature of -75°C were also used. The other camera equipped was a Complementary Metal-Oxide Semiconductor camera from Hamamatsu (Orca-Quest qC-MOS C15550-20UP, Hamamatsu, Japan). All images were acquired though the LAS X software ((Leica Microsystems, Germany). A Samsung Galaxy S22 (Samsung, Japan) equipped with a CMOS cell phone camera was used to acquire images and presented in: Figure 5A, Figure 5B, Figure 5C, Figure 5E. At the inverted optical microscope an electrochemical cell was placed on the stage. In these experiments either a glassy carbon (CH Instruments, Austin, TX), Indium Tin Oxide (ITO) (Huany Co., China), or a graphitic carbon rod (diameter = 0.7 mm, Amazon.com, USA) working electrode was used. Figure 1A shows the different configurations of the 3-electrode electrochemical cell. All working electrodes were thoroughly polished using a polishing pad (Buehler, Lake Bluff, IL). The counter electrode used was a glassy carbon rod (CH Instruments, Austin, TX), or graphite rod (radius = 2.5 mm, L = 10.2 cm, Amazon.com, USA) for ITO working electrode or 2-electrode system, and the reference electrode was composed of a 1 M Ag / AgCl reference electrode (CH Instruments, Austin, TX) in a 1 M KCl agarose salt bridge. A schematic of the different 3-electrode experimental set up can be found in Figure 1A. Spectra were taken with a Go Direct® SpectroVis® Plus Spectrophotometer (Veirner, Beaverton, Oregon). All measurements were performed in a quartz cuvette (Malvern Panalytical, Westborough, MA). Absorbance spectra were taken using the incandescent light source inside the spectrophotometer. Fluorescence Spectra were taken by shining light through an opening in the bottom of the spectrophotometer with the 5x objective filtered by the Y3 filter (Leica Microsystems, Germany) that exhibits an excitation window of 532-558 nm. The ECL spectrum (Figure 2C) was taken using a modified electrochemical set up. Due to the size constraints of a 1 cm path length cuvette, a 0.7 mm in diameter graphitic rod was used as the working electrode, all the other electrodes remained the same. 3220-427902 PRF 70790-02 The 3-electrode electrochemical measurements were taken using a CHI 920D scanning electrochemical microscope (CH Instruments, Austin, TX). The glassy carbon working electrode (r = 1.5 mm, CH Instruments, Austin, TX) was polished using a clean polishing pad, rinsed with water and isopropanol. The ITO working electrode (Huany Co., China) was laser cut into pieces of 25 mm x 25 mm approximate dimensions. Then they were epoxied onto a glass tube ( r = 19 mm, h = 20 mm). The counter electrode was a glassy carbon rod (r=1.5 mm, L = 10 cm, CH Instruments, Austin, TX). For a reference electrode, a Ag / AgCl (1 M KCl) electrode was used with a saltbridge made of agarose and 1 M KCl inside a glass pipet. The 2 electrode electrochemical experiments were done with a small graphite rod working electrode (r=0.35 mm), and a large graphite rod quasi-reference counter electrode. The 9 V battery (Amazon.com, USA) was connected to the working and quasi-reference counter electrode through leads, then connected to the electrodes with alligator clips. ESR Spectra were collected on a Bruker EMX-PLUS (Bruker, Billerica, MA) in the Purdue Research Instrumentation Core. The samples of K2S2O8, Ru(Bpy)3Cl2, and [Ru(Bpy)3][SO4]•were placed into ESR sample tubes (ThermoFisher, USA). For the [Ru(Bpy)3][SO4]•, it was generated on a 2-electrode system, and tapped onto a clean weigh boat, then put into the EPR tube. At the EPR, the WinEPR acquisition software was used (Bruker, Billerica, MA). The Microwave Bridge Controller Window was used to tune the EPR first through the adjustment of the Frequency, Bias, Signal Phase, Attenuation, and Iris. Finally, the Auto Tune feature was used to finish the tuning. High concentrations of K2S2O8(50 mM) were used. A plausible reaction mechanism for solution-phase reductive coreactant ECL between the persulfate anion and [Ru(bpy)3]2+is shown in Figure 1B. Briefly, [Ru(bpy)3]2+is reduced to [Ru(bpy)3]+. The reduced luminophore may act as a reducing agent against the persulfate anion, with this reduction also corresponding to the decomposition of the peroxide bond forming [SO4]2-(not shown) and the [SO4]•-coreactant. This radical coreactant may then oxidize [Ru(bpy)3]+to the excited state [Ru(bpy)3]2+*, which then may radiatively decay to emit a photon. In the instant examples, the high sulfate and sulfate radical concentration profile found at the surface of the electrode, when a potential is applied, causes the nucleation and growth of the crystal structures through electroprecipitation. In fact, when [Ru(bpy)3]2+is mixed with K2SO4, an orange precipitate forms, implying the sulfate salt replaced the chloride ligands in Ru(bpy)3Cl2and precipitates. 3220-427902 PRF 70790-02 EXAMPLE 1 To establish that the ECL signal from the crystals was originating from the emission of [Ru(bpy)3]2+, the emission spectrum was collected (Figure 1A). Additionally, visible absorption (Figure 2A) and photoluminescence (Figure 2B) spectra were acquired of the 154x dilute liquid phase system. The dilutions were necessary considering the linear range of the spectrophotometer. In the absorbance spectrum, the metal center to ligand transition can be seen at ca.410 nm. The photoluminescence spectrum shows the λmax at 612 nm. Then, the ECL spectrum (Figure 2C) was taken using a modified electrochemical set up. The ECL spectrum signal was low compared to the photoluminescence spectrum (Figure 2B); thus, the peak was not well resolved. The λmaxwas best estimated at 620 nm. An example of the electrochemical experiment is shown in Figure 2D. A 0 V step formed the quiet time of the experiment for the first 5 s, shortly followed by the application of -1.65 V for a duration of time (shown as 100 s). Finally, the applied potential returns to 0 V, or the leads are disconnected, and the electrochemical signal acquisition was stopped once the light acquisition was finished being collected. ECL microscopy was used to visualize the electroprecipitation and growth of the crystals (Figure 3B). After the onset potential at 0 s, the crystals started to grow (Figure 3A, 1.33 s). These crystals were observed to extend beyond the electrode-insulator interface as seen in Figure 3A between 23.92-193.81 s. ECL microscopy performed in the face-on view with a 5x objective and an EMCCD camera. The ECL signal intensity becomes more heterogeneous with time, and as crystals start to nucleate and grow, the tips of the crystals show marked increase in intensity. To gain insight into the three-dimensional geometry that the crystals grow in, a profile view was used to view from the height of the crystal growth (Figure 3B). Similar to the face- on view, the tips of the crystals have an increased ECL signal. At the end of the experiment, the crystals grew to ca. 170 μm away from the surface of the electrode. This is an interesting observation since ECL is considered primarily a surface-confined process (a couple of microns) proximal to the electrode and many attempts have been made to enhance ECL’s spatial ability into three-dimensions including through-space ECL, 3D ECL, and ECL swimmers. At the start of the experiment, there is no visual nucleation of the crystals. The light was emitted close (<10 μm) to the electrode surface. After the nucleation event occurred, the crystals grew to emit light hundreds of microns away from the surface of the electrode. After the potential was returned to 0 V, or the leads were unclipped, the crystals began to dissolve and emit light, with a higher ECL signal at the tip of the crystal. This dissolution 3220-427902 PRF 70790-02 process is related to the geometry of the electrode. For a glassy carbon electrode, since their electroactive surface is facing down, the crystals rapidly fell off the electrode surface after the cessation of the applied potential due to gravity. Falling away from the surface also corresponded to moving away from the sulfate concentration gradient that was present at the surface of the electrode due to the reduction of the persulfate anion. In result, this allowed the electroless afterglow dissolution emission process to occur at a faster rate. However, on an optically transparent electrode such as an indium tin oxide (ITO) coated glass side with the electroactive area facing up, gravity no longer pulled the crystals away from the surface of the electrode, resulting in a prolonged afterglow chemiluminescence time of up to ten minutes. The chemiluminescence lifetime depends on the applied potential duration. For example, with 100 s of applied potential, the afterglow ECL can last for longer than a minute; however, with 30 s of applied potential the afterglow is limited to around 20 s. Without being bound by any theory, increased time of the applied potential may result in more crystals that may nucleate, and the crystals present may grow larger. Figure 4A depicts the dissolution afterglow ECL response of the crystals after they grew for 30 s. Individual crystals can be seen shortening in length (dissolving) after the potentiostat ended. The smaller pulse time generates fewer and smaller crystals, which was advantageous for optically viewing the dissolution processes due to their initial rapid growth and overlap, as shown in Figures 3A and 3B, during the application of the potential. After the potential was stopped at 30 s, the crystals emitted photons for nearly another 15 s. An interesting observation in the afterglow processes is that the tips of the crystals, where dissolution and mass transfer are both fastest, appear brighter. Without being bound by any theory, the results may be the result of a greater surface area available at the tips for the dissolution processes to occur. Figure 4B presents the intensity of the afterglow chemilumninescence with respect to time for an experiment that had an applied potential for 100 s. The initial spike was observed from the shutoff of the potentiostat discharge. Once the dissolution process started (at 100 s) there was an increase in the signal until 152 s. Without being bound by any theory, the results are also supported by the dissolution hypothesis that as more crystals dissolve, there is progressively greater crystal surface area exposed. The increasing signal trend continued until there was a semi-uniform layer of crystals on the surface of the electrode, then the signal decreased (152-163 s) as those final crystals dissolved into solution. In a separate experiment, 50 s of potential was applied to an ITO working electrode. After the applied potential stopped, the leads were disconnected, and the solution was decanted. 3220-427902 PRF 70790-02 The cell was then dried with nitrogen continuously. Once the cell was dry, fluorescence microscopy was used to examine the surface of the electrode (Figure 4C). The dried crystals formed in the experiment did not chemiluminescence; but, fluoresced under excitation conditions (Fig. 4C). This experiment indicates that the original luminophore was part of the crystal and that solid-state ECL was not at play. To further understand this system, several control experiments were performed to investigate the mechanism. One of the first goals was to ensure that the chemiluminescence originated from the crystals. The main observations support this are: 1.) Chemiluminescence is only observed when the precipitate is present, and 2.) the dried crystals do not chemiluminescence and require an incident light to fluoresce (Figure 4C). The hypothesis that precipitation based on solubility equilibria is responsible for crystal formation was further explored. In an experiment, 100 mM potassium sulfate (K2SO4) was mixed in an equimolar solution of Ru(bpy)3Cl2 (10 mM). An orange precipitate formed almost immediately in both trials with the addition of the water-acetonitrile solution (Figure 5A and 5B) and exhibited no chemiluminescence capabilities. This experiment validates that the presence of sulfate forms a precipitate with Ru(bpy)32+, indicating that if the precipitation is faster than the lifetime of the electrogenerated radical, a portion of the precipitate will be at least one radical species. One important mechanistic consideration is identifying which luminophores (precipitated versus freely diffusing) were responsible for the electroless ECL. In an experiment, a 2-electrode system, composed of a smaller graphite rod as the working electrode, and larger graphite rod as the quasi-reference counter electrode, were connected to a 9 V battery. After some time (30 s – 60 s) of applied potential to a solution of 10 mM [Ru(bpy)3]2+, 50 mM K2S2O8, and 100 mM KCl, the electrode was disconnected and placed in another scintillation vial. The secondary scintillation vials contained water, acetonitrile, water- acetonitrile at 50 / 50 % v / v, 50 mM K2S2O8 in water-acetonitrile at 50 / 50 % v / v, and 10 mM [Ru(bpy)3]2+in water-acetonitrile at 50 / 50 % v / v. Only the last solution produced light from the afterglow processes in the transferred vial. Thus, the solution phase [Ru(bpy)3]2+must be participating in the electroless afterglow chemiluminescence (Figure 5C). The bright tips of the crystals offered valuable insight into the mechanism, implicating not only dissolution but the mass transfer of a freely diffusing species in the electroless ECL reaction. This implies that any Ru(bpy)32+that is co-crystallized is not sufficient to show chemiluminescence, implying the crystal is largely made up of Ru(bpy)3+and SO4•-. 3220-427902 PRF 70790-02 Two experiments were performed to validate the formation of radicals in the crystal. In the first, a radical scavenger, such as 10 mM potassium hexacyanoferrate (II), was introduced into the system. Upon addition, the ECL afterglow lifetime decreased. Moreover, the signal shape changed significantly, not showing the expected large increase in signal as the dissolution occurred, rather the trace took a larger, broader signal (Figure 5D). Electron Spin Resonance spectroscopy was used to confirm the presence of a radical species within the crystal, and control experiments suggest the species is SO4•-. Figure 6A and 6C show the large signal originating from the dried crystals after the electroprecipitation occurs. This is contrasted to the much smaller signal from K2S2O8 and the Ru(bpy)3Cl2 controls. One other important observation was that when the crystals fell off the electrode, they continued to electrolessly chemiluminescence with no significant decrease in the afterglow lifetime (Figure 5E). The results indicate that the afterglow ECL response exhibited by the persulfate anion- [Ru(bpy)3]2+system is caused by the nucleation, and subsequent growth, of crystals at the surface of the electrode that contain the reactive sulfate radical anion and the reduced form of the luminophore. After the applied potential is turned off, the crystals gradually dissolve while emitting light. The mechanism by which this occurs is presented below and illustrated in Figure 1C. The chromophore and the co-reactant are simultaneously reduced at an electrode: [Ru(bpy)3]2+(aq) + e- ^ [Ru(bpy)3]+(aq) Eappl< -1.5 V Equation 1 Eappl < -1.5 V Equation 2 form of the chromophore and the sulfate radical anion co-precipitate: [SO4]•-(aq) + [Ru(bpy)3]+(aq) ^ [Ru(bpy)3] [SO4]•(s) Eappl< -1.5 V Equation 3 The electrode is turned off the leads are disconnected, allowing the precipitate to slowly redissolve (or dissolve in a different container containing the original form of the luminophore): [Ru(bpy)3] [SO4]•(s)^ [SO4]•-(aq) + [Ru(bpy)3]+(aq) Eappl= OFF Equation 4 [SO4]•-(aq) + [Ru(bpy)3]2+(aq) ^ [Ru(bpy)3]3+(aq) + SO42-(aq) Eappl= OFF Equation 5 [Ru(bpy)3]3+(aq) + [Ru(bpy)3]+(aq) ^ [Ru(bpy)3]2+(aq) + [Ru(bpy)3]2+*(aq) Eappl= OFF Equation 6 [Ru(bpy)3]2+*(aq) ^[Ru(bpy)3]2+(aq) + hn , lmax = 620 nm Eappl= OFF Equation 7 3220-427902 PRF 70790-02 Equations 4-7 persist until the precipitate is completely dissolved. To generalize this system beyond the co-electroprecipitation of [Ru(bpy)3][SO4]•, calcium chloride (10 mM) and potassium persulfate (50 mM) were used to co-crystalize to [Ca][SO4]•2. The setup was the same as in the electrode transfer experiments. A partial bulk electrolysis was performed to generate a mixed solution of [Ru(bpy)3]2+ / +that was housed in a secondary scintillation vial as both are needed for the generation of afterglow electrochemiluminescence given the above mechanism (Eq. 1 – Eq. 7). After the electrode is transferred to the secondary scintillation vial, the precipitate emits photons. Thus, the sulfate radical can be co-crystalized with other cations beyond [Ru(bpy)]+. In totality, this set of experiments can be expanded to a generalized framework of precipitating the radical anion along with a cation as an aqueous insoluble salt utilizing the concentration gradient formed by the application of the potential to the system. The principle of flash-crystallization is based on the ability to tune concentration profiles at electrified interfaces that exceed the solubility equilibrium, resulting in a precipitate that contains radicals. This flash-crystallization can amplify the lifetime of electrochemiluminescence by orders of magnitude, allowing one to observe chemiluminescence from electrogenerated radicals electrolessly dissociated from time. The co- reduction of [Ru(bpy)3]2+and persulfate anion coreactant forms crystals composed of both [Ru(bpy)3]+and SO4•-, as confirmed through control experiments and ESR. By using ECL microscopy, the nucleation, growth, and dissolution of the crystals was monitored. Once the crystals nucleated, the electrified interface can be disconnected from the power source, causing crystals to re-dissolve, releasing both [SO4]•-and [Ru(bpy)3]+into the solution. The [SO4]•-can act as a strong oxidizing agent against the solution-phase [Ru(bpy)3]2+ to form [Ru(bpy)3]3+, which then can undergo an annihilation reaction with the re-dissolved and solvated [Ru(bpy)3]+to form the excited state [Ru(bpy)3]2+*, which can then radiatively decay.

Claims

3220-427902 PRF 70790-02 WHAT IS CLAIMED IS 1. A solid composition comprising a salt of a sulfate radical anion and a counter ion.

2. The composition of claim 1, wherein the salt is a solid precipitate.

3. The composition of claim 1, wherein the counter ion comprises a cation selected from the group consisting of an alkali metal an alkaline-earth metal, or a transition metal.

4. The composition of claim 1, wherein the salt comprises the formula [Ca][SO • 4]2.

5. A method of remediating a per- and / or polyfluoroalkyl substance (PFAS), the method comprising: contacting the PFAS in an aqueous medium (e.g., a first aqueous medium) with a sulfate radical anion, thereby degrading the PFAS.

6. The method of claim 5, further comprising: providing the sulfate radical anion to the aqueous medium (e.g., the first aqueous medium) comprising the PFAS.

7. The method of claim 6, wherein the step of providing comprises: forming the sulfate radical anion in the aqueous medium (e.g., the first aqueous medium) (i.e., in situ).

8. The method of claim 6, wherein the step of providing comprises: forming the sulfate radical anion in a second aqueous medium (e.g., ex situ), wherein the second aqueous medium is different than the aqueous medium (e.g., the first aqueous medium), and adding the sulfate radical anion to the aqueous medium (e.g., the first aqueous medium).3220-427902 PRF 70790-02 9. The method of claim 8, wherein the step of forming precipitates a salt comprising the sulfate radical anion and a counter ion in the second aqueous medium.

10. The method of claim 9, wherein the step of adding dissolves the salt and releases the sulfate radical anion into the aqueous medium (e.g., the first aqueous medium).

11. The method of claim 9, wherein the salt is a solid precipitate.

12. The method of claim 9, wherein the counter ion comprises a cation selected from the group consisting of an alkali metal an alkaline-earth metal, or a transition metal.

13. The method of claim 9, wherein the salt comprises the formula [Ca][SO • 4]2.

14. The method of claim 5, wherein the step of contacting oxidizes the PFAS.

15. A method of preparing a composition according to claim 1, the method comprising: applying a potential at an electrode to a solution comprising a reactant and a counter ion in a solvent, thereby forming the composition comprising a salt of a sulfate radical anion and a counter ion.

16. The method of claim 15, wherein the reactant is selected from the group consisting of tri-n-propylamine, oxalate anion, persulfate anion ([S2O8]2-), benzoyl peroxide, and any combination thereof; preferably the reactant is persulfate anion.

17. The method of claim 15, wherein the solution has a molar ratio of the counter ion to the reactant of about 1:1 to about 1:15, preferably about 1:2 to about 1:10, more preferably about 1:4 to about 1:

6.

18. The method of claim 15, wherein the solution has a concentration of the counter ion of about 1 mM to about 50 mM, preferably about 1 mM to about 20 mM, and a concentration of the reactant of about 1 mM to about 100 mM, preferably about 20 mM to about 100 mM.3220-427902 PRF 70790-02 19. The method of claim 15, wherein the electrode is selected from the group consisting of a working electrode (e.g., a glassy carbon rod, a graphite rod, an Indium Tin Oxide (ITO) electrode), a counter electrode (e.g., a glassy carbon rod, a graphite rod), a reference electrode (e.g., an Ag / AgCl electrode in a salt bridge), and any combination thereof.

20. The method of claim 15, wherein the step of applying reduces the reactant to provide the sulfate radical anion.

21. The method of claim 15, wherein the step of applying nucleates the sulfate radical anion and the counter ion to form the salt on a surface of the electrode.

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