Electron Spin Resonance Studies Research Articles

Electron paramagnetic resonance proof for the existence of molecular hydrino

Quantum mechanics postulates that the hydrogen atom has a stable ground state from which it can be promoted to excited states by capture of electromagnetic radiation, with the energy of all possible states given by En = −13.598/n2 eV, in which n ≥ 1 is a positive integer. It has been previously proposed that the n = 1 state is not the true ground state, and that so-called hydrino states of lower energy can exist, which are characterized by fractional quantum numbers n = 1/p, in which 1 < p ≤ 137 is a limited integer. Electron transition to a hydrino state, H(1/p) is non-radiative and requires a quantized amount of energy, 2mE1 (m is an integer), to be transferred to a catalyst. Numerous putative hydrino-forming reactions have been previously explored and the products have been characterized by a range of analytical methods. Molecular hydrino has been predicted to be paramagnetic. Here, we give an account of an electron paramagnetic resonance (EPR) study of molecular hydrino H2(1/4) that was produced as gaseous inclusion in polymeric Ga(O)OH by a plasma reaction of atomic hydrogen with non-hydrogen bonded water as the catalyst. A sharp, complex, multi-line EPR spectrum is found, whose detailed properties prove to be consistent with predictions from hydrino theory. Molecular hydrino was also identified in gas chromatography as a compound faster than molecular hydrogen.

Magnetic properties of the mononuclear iron (III) complexes with biphenyl‐disubstituted Schiff base ligand: EPR and SQUID study

The magnetic features of the mononuclear iron (III) complexes [Fe(L)2]+X−with tridentate Schiff base ligands [where L is 4‐(4‐diphenylcarboxy)‐2′‐oxysalicylidene‐N′‐ethylene‐N‐ethylene‐2′‐amine‐(carboxy‐4‐diphenyl) and X− = Cl−(1), PF6−(2) and NO3−(3) counter‐ions] have been studied by electron paramagnetic resonance (EPR) spectroscopy, SQUID (superconducting quantum interference device) magnetometry (solid), and Evans1H nuclear magnetic resonance method (solution). EPR established that compounds (1) and (2) consist of two types high‐spin (HS, S = 5/2) centers with weak distorted and strong low‐symmetry octahedral crystal fields. The signals from low‐spin centers (LS, S = 1/2) of Fe (III) are observed in the spectra of compounds2and3. SQUID revealed permanent HS behavior in (1) and mixed LS + HS in (2), (3) in wide temperature range, while solution method—only HS. Magnetic measurements allowed to estimate part of HS and LS fractions and detected antiferromagnetic exchange interactions between the neighboring Fe (III) ions in complexes.“

Synergistic effect of hierarchical structure and S-scheme heterojunction over O-doped g-C3N4/N-doped Nb2O5 for highly efficient photocatalytic CO2 reduction

Reasonable construction and engineering of optimal hierarchical photocatalysts have garnered great attention in terms of promoting CO2 photoreduction into fuel production. Herein, we introduce a novel 3D O-doped g-C3N4/N-doped Nb2O5 (OCNNb) S-scheme heterojunction fabricated using control of each material's surface charge-induced heteroaggregation for photocatalytic CO2 reduction (PCR). The optimized sample converts CO2 with substantially greater rates (the sum production rate of CO and CH4) than the blank control, i.e., O-doped g-C3N4 (OCN) and N-doped Nb2O5 (NNBO). The enhanced photocatalytic efficiency can not only be ascribed to the prevention of photogenerated charge carrier recombination mediated by the S-scheme heterojunction but also to the high specific surface areas and abundance of active sites. In the meantime, work function measurement, in situ irradiated, X-ray photoelectron spectroscopy and electron paramagnetic resonance (EPR) studies confirm the S-scheme photogenerated charge transfer mechanism. This study offers a useful approach for fabricating extremely effective heterojunction photocatalysts to convert solar fuels.

Effects of Gamma Irradiation on Free Radical Components, Phenolic Content and Antioxidant Activity of Beebread

Antiradical activity and free radicals before and after gamma-treatment of beebread were investigated by Electron Paramagnetic Resonance (EPR) spectroscopy. A narrow signal the intensity of which increased with the dose was assigned to O-centred free radicals induced by gamma rays. They are stable for 120 days after irradiation. The irradiation effect on antioxidant potential and content of phenolic compounds were studied. It was found that total phenolic and flavonoid content values increased after beebread irradiation depending on the dose. The antiradical activity of extracts was assessed by the DPPH free radical scavenging activity. The EPR study showed that it increased after irradiation with 5 kGy (27%) and 20 kGy (19%), while the slight decreasing (6%) was observed after irradiation at 10 kGy.

Electrochemical, EPR, and quantum chemical study of reductive cleavage of cone‐Calix[4]arene nosylates – New electrosynthetic approach

AbstractThe mechanism of electrochemical reduction of a series of six cone‐calix[4]arene‐bis‐nosylates (4‐nitrophenylsulfonate aryl esters) was investigated on mercury electrodes using DC‐polarography and cyclic voltammetry (CV) combined with in situ electron paramagnetic resonance (EPR)‐spectroelectrochemistry in aprotic dimethylformamide. Model compounds – expected fragments and products ‐ were studied for comparison. The experimental results are supported by quantum chemical calculations. All calix[4]arene‐bis‐nosylates are reduced in a first reversible step to bis‐(radical anion) by two simultaneous one‐electron transfers. Each of the two electrons is unpaired and separately localized on two nosylate groups.In the second reduction step next 2×2 electrons are transferred and both sulfonate ester groups are cleaved to two 4‐nitro‐benzenesulfinate ions and a calixarene bis‐phenolate (95%). This electroreductive generation of arylsulfinate anions is a significant finding from the electrosynthetic point of view. Activated arylsulfinates, the synthesis of which is generally difficult, can be easily prepared by electrochemical reduction of the nosyl esters.

Diselenide as a Dual Functional Mechanophore Capable of Stress Self-Reporting and Self-Strengthening in Polyurethane Elastomers

Diselenide as a Dual Functional Mechanophore Capable of Stress Self-Reporting and Self-Strengthening in Polyurethane Elastomers

Synthesis of Expanded Crowned Macrocycles Containing Two Pyrrolo[1,2‐a]indole Units

AbstractExpanded crowned macrocycles containing two pyrrolo[1,2‐a]indole moieties in their macrocyclic framework have been synthesized by condensing a 1,4‐bis(2‐thienyl) benzene‐based diol with three different crown based tripyrranes under acid‐catalyzed conditions. HRMS and NMR studies were used to deduce the molecular structures of fused expanded crowned macrocycles. The studies indicated the occurrence of two intramolecular fusions between two core pyrrolic nitrogens with carbon atoms of two phenylene groups to generate two pyrrolo[1,2‐a]indole moieties as a part of expanded porphyrin framework. DFT studies indicated that the macrocycles are highly nonplanar and adopt a trapezoidal structure. The absorption spectral studies showed that the macrocycles exhibit three bands in 350–520 nm region and electrochemical studies indicated the electron‐rich nature of the macrocycles. Furthermore, the expanded crowned macrocycles form stable cation radicals upon treatment with trifluoroacetic acid as judged from absorption, electron spin resonance studies, and the cation radicals that formed absorb strongly in the NIR region. TD‐DFT studies corroborate with the experimental observations.

Solar energy-driven upcycling of plastic waste on direct Z-scheme heterostructure of V-substituted phosphomolybdic acid/g-C3N4 nanosheets

The increasingly massive consumption of plastics is becoming a global pollution disaster, with serious environmental and economic problems. Here we report an efficient and sustainable strategy for the visible-light-driven upcycling of various plastic wastes into high-value-added formic acid. We firstly design and fabricate a self-assembly Z-scheme heterostructure of V-substituted phosphomolybdic acid clusters/g-C3N4 nanosheets (VPOM/CNNS). The Z-scheme charge transfer process is unambiguously elucidated by transient absorption spectra and electron spin resonance studies, which endow VPOM/CNNS heterostructure with efficient charge separation and strong redox potentials. Consequently, VPOM/CNNS heterostructure displays a superior photocatalytic performance toward upcycling of various plastics. The optimal VPOM/CNNS composite exhibits a remarkable formic acid production rate of 24.66 μmol h−1 g−1 for upcycling of polyethylene, which is 262-fold higher than that of pristine CNNS. This work highlights the potential of Z-scheme heterojunction as an unusual tool for the photo-driven upcycling of plastic waste.

Emission and EPR studies on green and red color emitting gallate phosphor containing manganese/chromium ions

The ZnGa2O4:Mn2+/Cr3+ ceramic phosphor is synthesized via high temperature solid state reaction method and then phosphor is intensively studied for green/red color emission. Prepared samples are structurally characterized through powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) and it is found that the samples possess single phase cubic spinel structure. The X-ray photoelectron spectroscopy (XPS) is performed for the identification of chemical states of different elements present in the samples. The Zn0.9Ga2O4:0.1%Mn2+ sample has shown broad emission band (475–575 nm) having peak at 505 nm (green) due to the electronic transition of Mn2+ ion. The ZnGa1.9O4:0.1%Cr3+ sample has shown intense emission at 696 nm (deep red) due to the 2E (2G) →4A2(4F) transition of Cr3+ ions. The co-doped Zn0.9Ga1.9O4:Mn2+/Cr3+ sample on the other hand can be excited with different excitations to give green and red emissions. Electron paramagnetic resonance (EPR) spectroscopy is done to inspect defects caused by the substitution of Ga3+ and Zn2+ by Cr3+ and Mn2+ ions, respectively. Emission decay measurements are done to decipher afterglow and photoluminescence decay.

An EPR study of gamma irradiated mixed materials based on sucrose for dosimetric purposes

Since the recent past it was known that sucrose showed some good results as dosimeter using Electron Paramagnetic Resonance (EPR) technique. However there is still considerable interest in improving its accuracy and precision as well as in developing new systems with improved characteristics. In view of this fact, materials consisting of mixture at two different ratios (70:30 and 50:50%) between sucrose and ascorbic acid, sucrose and cysteine and sucrose and diphenylamine were studied by EPR spectroscopy. The obtained new materials were irradiated by γ-rays having doses varying from 0.5 up to 20 kGy. Before irradiation no EPR spectra were recorded. After irradiation complex EPR spectra with dominants of the sucrose spectrum in them were observed. The influence of the instrumental settings on the EPR signal intensity was reported. It was found out that the dose response of sucrose has linear dependence up to 20 kGy. The dose response of the new materials is compared with those in case of sucrose. The results showed that the addition of ascorbic acid, cysteine and diphenylamine to sucrose were leading to decrease in its sensitivity, but the EPR dose response remains unchanged. It was supposed that the decrease in the sensitivity was probably due to the antiradical activity of the added substances. To check this assumption the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity (FRSA) of the used substances was studied. It was concluded that these mixed materials can be used for dosimetric purposes, however they have lower sensitivity compared to sucrose.

Rapid access to polycyclic N-heteroarenes from unactivated, simple azines via a base-promoted Minisci-type annulation

Conventional synthetic methods to yield polycyclic heteroarenes have largely relied on metal-mediated arylation reactions requiring pre-functionalised substrates. However, the functionalisation of unactivated azines has been restricted because of their intrinsic low reactivity. Herein, we report a transition-metal-free, radical relay π-extension approach to produce N-doped polycyclic aromatic compounds directly from simple azines and cyclic iodonium salts. Mechanistic and electron paramagnetic resonance studies provide evidence for the in situ generation of organic electron donors, while chemical trapping and electrochemical experiments implicate an iodanyl radical intermediate serving as a formal biaryl radical equivalent. This intermediate, formed by one-electron reduction of the cyclic iodonium salt, acts as the key intermediate driving the Minisci-type arylation reaction. The synthetic utility of this radical-based annulative π-extension method is highlighted by the preparation of an N-doped heptacyclic nanographene fragment through fourfold C–H arylation.

Protein engineering and biochemical/biophysical approaches for structural studies of small membrane proteins and their complexes: Application to viroporins

We study the structure and function of small viral membrane proteins, which are expressed in the host and function in cellular membranes. Typically, they are multi‐domain multi‐functional proteins aiding virus adaptation and proliferation. Detailed characterization of the structure‐function relationship of these proteins will help to better understand virus‐host interactions and possibly develop protein inhibitors. However, such characterization is challenging due to the proteins’ small size and dynamic nature. Our focus is on viroporins, namely the Vpu, p7 and E proteins from HIV‐1, HCV, and CoV, respectively. Viroporins form ion‐conducting oligomers in cellular membranes leading to increased membrane permeability affecting ion homeostasis in infected cells. In addition, these proteins have soluble domains involved in interactions with host proteins. Currently, the structures of full‐length viroporins are largely uncharacterized and the information about the mechanism of oligomer formation and inter‐domain communication is very limited. Here, we report our effort to produce and solve the structure of stable viroporin oligomers in lipid environment. We use protein engineering to generate a range of fusion constructs aiming to increase the protein/oligomer size and reduce the conformational heterogeneity, thus making the protein amenable for structural determination by electron microscopy (EM) techniques. We produced, expressed in E. coli and purified, several soluble constructs of Vpu, p7 and E proteins fused at their N‐terminals to maltose binding protein (MBP). Thereafter, we interacted these proteins with lyso lipid mixtures of PC and PG, and their oligomerization was observed by negative staining EM and pulse electron paramagnetic resonance (EPR). We further use size‐exclusion chromatography (SEC) to assess the heterogeneity of viroporin oligomers in lyso PC/PG. Indeed, the protein elution exhibits a relatively broad chromatographic profile, indicating the presence of more than one oligomeric form. We further use SEC to test different protein‐to‐lipid molar ratios and the effect of viroporin inhibitor binding, aiming to shift the equilibrium toward stable functional viroporin oligomers. We will also discuss results from EM studies on these stable oligomers and EPR studies on spin‐labeled viroporin assembly. The progress we made in generating protein constructs and assessing protein oligomerization and stability in lipid provides a great promise for the development of successful methodology to determine the structure of full‐length viroporin. This methodology could also be applicable to other small oligomeric membrane proteins.

Production of recombinant Mtb membrane efflux pump for structural and functional studies to reveal mechanisms of drug resistance

We investigate the molecular mechanisms of the Mycobacterium tuberculosis (Mtb) EfpA membrane exporter. EfpA is a ca. 56 kDa monomeric integral membrane protein, which belongs to the Major Facilitator Superfamily transporters, and the QacA subfamily. It has fourteen predicted transmembrane segments/helices (TMs) with both N‐and C‐termini located in the intracellular space. EfpA exports anti‐Mtb drugs (e.g., isoniazid, fluoroquinolones, rifampicin, tetracycline, clofazimine) out of the cell coupled to the antiport of H+. Thus, EfpA supports a major mechanism of Mtb drug resistance. However, its structure and structure‐function relationship are currently poorly understood. What is more, to the best of our knowledge, the protein was not produced recombinantly in quantities needed for large‐scale in vitro investigations. To overcome this deficiency, we cloned the gene encoding EfpA and expressed the protein in E. coli host. Two fusion constructs of EfpA with respectively His8‐FLAG tag and His8‐maltose binding protein (MBP) tags were produced. These tags were designed to facilitate protein purification utilizing double affinity chromatography. We used SDS‐PAGE and western blotting to identify the protein localization in E. coli cellular fractions. We found that although these fusion constructs were expressed to a minor extent in the E. coli plasma membrane and can be partially purified, the proteins were mostly deposited in inclusion bodies, similarly to what was observed previously for other Mtb membrane proteins. We purified to a high degree and refolded these proteins from inclusion bodies. Currently, we are working on producing large quantities of highly‐pure EfpA protein for functional and structural studies. We further used Swiss Model program and the structures of the distant homologues NorC transporter and peptide transporter DtpA solved in outward‐ and inward‐facing states, respectively, to predict the structure of EfpA in the two major functionally‐relevant conformations. After that, we designed two double cysteine EfpA mutants E141C/F398C and F170C/Q401C, which report on large conformational rearrangements upon transition from outward‐ to inward‐facing conformations, for spin labeling and electron paramagnetic resonance (EPR) study. These mutants were generated via site‐directed mutagenesis on the background of cysteine‐free EfpA construct and are being produced in E. coli. We will further discuss results from EfpA‐drug binding and EPR experiments. Our studies have the potential to significantly advance the detailed characterization of EfpA functional mechanism.

Photoluminescence and electron paramagnetic resonance studies of Mn2+doped CaAl4O7

Manganese doped polycrystalline CaAl4O7 samples with doping concentrations in 0.1–2.0 mol% range were synthesized using the solid-state synthesis method. Photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy techniques were applied to characterize the local structure and properties of Mn ions in CaAl4O7. With excitation of 406 nm, Mn2+ exhibited a wide emission band centered at 572 nm with luminescence decay time 6.5–8.3 ms. The results of EPR and X-ray diffraction (XRD) analyses evidenced preferential incorporation of Mn2+ in the seven-fold coordinated site of Ca2+.

Doping strategy-tuned non-radical pathway on manganese oxide for catalytic degradation of parabens

Non-radical oxidation processes with singlet oxygen (1O2) and mediated electron transfer have emerged as efficient methods for the selective degradation of aqueous pollutants in peroxymonosulfate (PMS)-based catalytic systems. On this basis, in this study, transition- and lanthanide-metal co-doped manganese oxide octahedral molecular sieve (Cu-Nd-OMS-2) was synthesized, characterized, and tested in the degradation of aqueous parabens. Methylparaben (30 mg/L) was degraded at 100% and mineralized at 92% within 40 min in the presence of Cu-Nd-OMS-2 and PMS (200 mg/L) in pH scale ranging from 3 to 8. Compared with pristine and mono-doped catalysts, the Cu-Nd-OMS-2, produced by the doping strategy, exhibited a superior catalytic activity for the oxidative degradation of several parabens through turning the mechanism with radicals into non-radical pathway. Electron paramagnetic resonance, quenching experiments and mechanism study indicated that 1O2 and mediated electron transfer contributed to the removal of parabens. Besides, the redox cycle of Mn(III)/Mn(IV) might be responsible for PMS activation, and abundant surface hydroxyl groups as well as oxygen vacancies on the catalyst further promoted the adsorption of pollutants and the generation of 1O2. Overall, the present study provides a novel and facile doping strategy on manganese oxide catalysts for fine-tuning radical/non-radical processes towards PMS-based water remediation.

Activation of peroxymonosulfate by MnFe2O4@BC composite for bisphenol A Degradation: The coexisting of free-radical and non-radical pathways

In this study, novel metallic oxide catalyst MnFe2O4@biochar composite was synthesized by sol–gel pyrolysis loading of MnFe2O4 on biochar, and then used to activate peroxymonosulfate (PMS) to degrade bisphenol A (BPA). Characterization results demonstrated that the Fe and Mn oxide particles were homogeneously distributed on the surface of biochar, which avoided the aggregation of metal oxides. The strong magnetism of the composite was conducive to recycling during practical application. In the PMS system activated by MnFe2O4@biochar composite, the removal rate and mineralization rate of 20 mg/L BPA reached 100% and 95.9% within 30 min, respectively. The quenching experiments and electron paramagnetic resonance (EPR) study verified the coexistence of free-radical and non-radical pathways in the MnFe2O4@biochar/PMS system, with O2•- as the dominant active species, followed by singlet oxygen (1O2). The catalytic degradation process could adapt a wide pH range from weak acid to the alkaline matrix and showed negligible influence by anions and humic acid. The characterization results confirmed the synergistic effect of the bimetal, proving that the introduction of biochar and second metal source into iron-based catalyst played an important role in the composite. Overall, the MnFe2O4@biochar showed promising performance in activating PMS for organic pollutant degradation in water with high stability and safe performance.

The effect of UV-B irradiation on structural and functional properties of corn and potato starches and their components

In this work, UV-B irradiation, an environmentally friendly modification method, was applied to corn and potato carbohydrates. The influence of irradiation on starch properties was compared with that observed for starch oxidation with NaClO. The changes in the structures of starch carbohydrates were investigated by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and chromatographic methods. Functional properties such as viscosity, water binding capacity and solubility as well as pasting characteristics and thermodynamic parameters of gelatinization, resulting from structural changes were determined. UV-B irradiation was found to be a milder modification method than chemical oxidation. The potato carbohydrates, especially amylose, appeared to be more susceptible to changes upon irradiation, whereas corn ones, particularly amylopectin, were more stable and their properties changed to a smaller extent. Similarly, functional properties were not significantly influenced by UV-B treatment. EPR studies revealed the mechanism of depolymerization of starch carbohydrates via formation of stable carbon-centered radicals.

Heat-activated persulfate oxidative degradation of ofloxacin: Kinetics, mechanisms, and toxicity assessment

• The mechanism of ofloxacin degradation by heat-activated persulfate were investigated. • Ofloxacin degradation in the system fitted well with the pseudo-first-order reaction model. • The four degradation pathways of ofloxacin were proposed. • The toxicity of ofloxacin and its intermediates was predicted. The widespread occurrence of fluoroquinolone antibiotics, such as ofloxacin (OFX), in natural water and soil has received increasing attention in terms of their potentially dangerous impacts on public health and ecosystems. In this study, the kinetics and mechanisms of OFX degradation by heat-activated persulfate (HAP) was investigated. Results showed that OFX degradation could be achieved effectively and fitted well with the pseudo-first-order reaction model in the HAP system. The OFX degradation efficiency was dramatically enhanced with increased temperature and initial persulfate dosage and inhibited in the presence of the common coexisting water matrices (e.g., bicarbonate, chloride, and humic acid). Quenching tests and electron paramagnetic resonance studies demonstrated the simultaneous contribution of both radicals with sulfate radicals having a slightly higher effect than hydroxyl radicals in the degradation process of OFX. Various intermediates of OFX degradation were characterized using High-performance liquid chromatography-Mass spectrometry (HPLC-MS), and detailed degradation pathways of OFX were proposed. And the toxicity of OFX and its intermediate products was predicted using the Ecological Structure-Activity Relationships (ECOSAR) and Toxicity Estimation Software Tools (TEST).

Estimation of Electron Distribution over Dinuclear Organometallic Molecular Wires by "IR Tag" Analysis of Ancillary Acyl-Cp Ligands.

Understanding the details of electronic properties of mixed-valence (MV) states of organometallic molecular wires is essential to gain insights into electron transfer phenomena. Although the field of MV chemistry is matured, there remain issues to be solved, which cannot be accessed by the conventional analytical methods. Here, we describe the synthesis and properties of diruthenium bridging (diethynylbenzene)diyl wires, (μ-p and m-C≡C-C6H4-C≡C){RuCpR(dppe)}2 1, with the acyl-substituted cyclopentadienyl rings [CpR: Cpe; η5-C5H4COOMe (a-series: ester derivatives), Cpa; η5-C5H4COMe (b-series: acetyl derivatives)], which are installed as IR-tags to estimate electron densities at the metal centers in the MV species. The electrochemical and IR/near IR-spectroelectrochemical studies reveal that the two metal centers in the para-isomers p-1a,b + interact with each other more strongly than those in the meta-isomers m-1a,b + . Electron-spin resonance study also supports the radicals being delocalized over the Ru-(p-C≡C-C6H4-C≡C)-Ru moieties in p-1a,b + . The spectroelectrochemical IR study shows significant higher-energy shifts of the ν(C=O) vibrations brought about upon 1e-oxidation. Spectral simulation on the basis of the Bloch equations allows us to determine the electron transfer rate constants (k et) between the two metal centers being in the orders of 1012 s-1 ( p-1 + ) and 109 s-1 ( m-1 + ). The shifts of the ν(C=O) bands reveal that the charge densities on the para-isomers p-1a,b + are widely delocalized over the Ru-(p-C≡C-C6H4-C≡C)-Ru linkages in contrast to the meta-isomers m-1a,b + , where the electron densities are mainly localized on the metal fragments, as supported by the density functional theory and time-dependent density functional theory studies as well as comparison with the reference mononuclear acetylide complexes, C6H5-C≡C-RuCpR(dppe) 2. We have successfully demonstrated that the carbonyl groups (>C=O) in the ancillary Cp ligands also work as IR-tags to report detailed information on the electron densities at the metal centers and the electron distribution over MV complexes as well.

Oxidation of ferumoxytol by ionizing radiation releases iron. An electron paramagnetic resonance study.

Ferumoxytol (FMX) is an iron oxide nanoparticle that is FDA approved for the treatment of iron deficiency anemia. FMX contains an Fe3O4 core. Currently, the redox chemistry of Fe3O4 nanoparticles remains relatively unexplored. FMX has recently gained interest as an anti-cancer agent. Ionizing radiation (IR) is a treatment modality employed to treat several types of cancer. Utilizing electron paramagnetic resonance (EPR) spectroscopy, we found that the products produced from the radiolysis of water can oxidize the Fe3O4 core of FMX. Because of the limited diffusion of the HO2• and HO• produced, these highly oxidizing species have little direct effect on FMX oxidation. We have determined that H2O2 is the primary oxidant of FMX. In the presence of labile Fe2+, we found that reducing species generated from the radiolysis of H2O are able to reduce the Fe3+ sites of the Fe3O4 core. Importantly, we also have shown that IR stimulates the release of ferric iron from FMX. Because of its release of iron, FMX may serve as an adjuvant to enhance radiotherapy.