Electron Spin Resonance Technique Research Articles

Silica-Supported Assemblage of CuII Ions with Carbon Dots for Self-Boosting and Glutathione-Induced ROS Generation

The present work introduces coordinative binding of CuII ions with both amino-functionalized silica nanoparticles (SNs) and green-emitting carbon dots (CDs) as the pregrequisite for the CuII-assisted self-assembly of the CDs at the surface of the SNs. The produced composite SNs exhibit stable in time stimuli-responsive green fluorescence derived from the CuII-assisted assemblage of CDs. The fluorescence response of the composite SNs is sensitive to the complex formation with glutathione (GSH), enabling them to detect it with the lower limit of detection of 0.15 μM. The spin-trap-facilitated electron spin resonance technique indicated that the composite SNs are capable of self-boosting generation of ROS due to CuII→CuI reduction by carbon in low oxidation states as a part of the CDs. The intensity of the ESR signals is enhanced under the heating to 38 °C. The intensity is suppressed at the GSH concentration of 0.35 mM but is enhanced at 1.0 mM of glutathione, while it is suppressed once more at the highest intracellular concentration level of GSH (10 mM). These tendencies reveal the concentrations optimal for the scavenger or reductive potential of GSH. Flow cytometry and fluorescence and confocal microscopy methods revealed efficient cell internalization of SNs-NH2-CuII-CDs comparable with that of “free” CDs.

Z-scheme 2D/2D WS2/Bi2WO6 heterostructures with enhanced photocatalytic performance

Herein, we designed and prepared a novel two-dimensional/two-dimensional WS2/Bi2WO6 heterostructure photocatalyst. Firstly, by first-principles calculations, we found that Bi2WO6 and WS2 could form a stable WS2/Bi2WO6 heterostructure with a type-II band alignment structure. Supporting by the theoretical prediction, a series of WS2/Bi2WO6 heterostructures with different amounts of WS2 were synthesized via a facile hydrothermal method. The WS2/Bi2WO6 heterostructures exhibited higher photocatalytic activity in degradation of rhodamine B and oxytetracycline under visible light irradiation than the pure Bi2WO6 and WS2. And the WS2/Bi2WO6 heterostructure had a large specific surface area and good photo-stability. The photoluminescence spectra and photoelectrochemical measurements showed that the WS2/Bi2WO6 heterostructure possessed the ability to facilitate the separation and transfer of photo-generated carries. The active species generated in the photocatalytic system were photo-induced holes, singlet oxygen, and superoxide anion, which were verified by the trapping experiments and electron spin resonance technique. Furthermore, a Z-scheme photocatalytic mechanism was proposed.

COMP (Cartilage Oligomeric Matrix Protein), a Novel PIEZO1 Regulator That Controls Blood Pressure.

Vascular endothelial cells are critical for maintaining blood pressure (BP) by releasing biologically active molecules, such as nitric oxide. A non-endothelial cell resident matricellular protein, COMP (cartilage oligomeric matrix protein), plays a pivotal role in maintaining cardiovascular homeostasis, but little is known about its regulatory effect on BP. Mice were infused with AngII (angiotensin II; 450 ng/kg per minute) for 3 days via an osmotic minipump, and BP was monitored by a tail-cuff system. Second-order mesenteric arteries were isolated from mice for microvascular tension measurement. Nitric oxide was detected by an electron paramagnetic resonance technique. Small-interfering RNA transfection, co-immunoprecipitation, bioluminescence resonance energy transfer assays, and patch-clamp electrophysiology experiments were used for further detailed mechanism investigation. COMP-/- mice displayed elevated BP and impaired acetylcholine-induced endothelium-dependent relaxation compared with wild-type mice with or without AngII. Inhibition of eNOS (endothelial nitric oxide synthase) abolished the difference in endothelium-dependent relaxation between wild-type and COMP-/- mice. Furthermore, COMP directly interacted with the C-terminus of Piezo1 via its C-terminus and activated the endogenous Piezo1 currents, which induced intracellular Ca2+ influx, Ca2+/calmodulin-dependent protein kinase type II and eNOS activation, and nitric oxide production. The Piezo1 activator, Yoda1, reduced the difference in endothelium-dependent relaxation and BP in wild-type and COMP-/- mice. Moreover, COMP overexpression increased eNOS activation and improved endothelium-dependent relaxation and BP. Our study demonstrated that COMP is a novel Piezo1 regulator that plays a protective role in BP regulation by increasing cellular Ca2+ influx, eNOS activity, and nitric oxide production.

Development of fluorescein-based dosimeter for radiation processing applications

Dosimetry forms an inseparable part of radiation processing. Many dosimeters are available to cover wide range of doses used in radiation processing. These include the Fricke, ceric-cerous, alanine ESR Alanine (Electron Spin Resonance Technique), dichromate, and radiochromic films. Low-dose radiation processing applications (<2 kGy) such as insect disinfestation, shelf-life extension, and sprout inhibition use imported dosimeters. At present, radiochromic films/waveguides are used for low-dose applications; however, the dosimeters are costly and subject to sanctions and supply restrictions from country of origin. The present work discusses the development of system that can be used as a routine dosimeter for radiation processing facilities in the dose range of 200–2500 Gy. Iodine is generated by the action of radiolysis products of water on iodide and iodate present. Generated iodine halogenates fluorescein to erythrosine with the help of bicarbonate. Increase in absorbance due to the formation of erythrosine can be related to the absorbed dose and used in routine dosimetric applications. As the change is radiochromic, it advantageously provides a visual indication of dose received.

EPR of copper centers in the prion protein.

Most proteins implicated in neurodegenerative diseases bind metal ions, notably copper and zinc. Metal ion binding may be part of the protein's function or, alternatively, may promote a deleterious gain of function. With regard to Cu2+ ions, electron paramagnetic resonance techniques have proven to be instrumental in determining the biophysical characteristics of the copper binding sites, as well as structural features of the coordinating protein and how they are impacted by metal binding. Here, the most useful methods are described as they apply to the prion protein, which serves as a model for the broader spectrum of neurodegenerative proteins.

EPR Study of the Mn-Doped Magnesium Titanate Ceramics

Manganese-doped magnesium titanate ceramic samples obtained by a solid-state reaction via sintering in the air from a mixture of MgO and TiO2 powders of different molar ratios were analyzed by electron paramagnetic resonance (EPR) technique. The EPR signals of Mn2+ ions (S = 5/2, І = 5/2) in crystal phases of MgO, Mg2TiO4, and MgTiO3 were detected. We have obtained the following spin Hamiltonian parameters for Mn2+ ions: g = 2.0015, A ∼81.0 × 10−4 cm−1 (in MgO phase); g = 2.0029, A ∼73.8 × 10−4 cm−1 , b 2 0 = 35 × 10−4 cm−1 (in Mg2TiO4 phase); g = 2.0040, A ∼79.0 × 10−4 cm−1 , b 2 0 = 165 × 10−4 cm−1 (in MgTiO3 phase). Despite the presence of Mn4+ centers in both Mg2TiO4:Mn and MgTiO3:Mn ceramics confirmed by previous optical studies, no EPR signals related to Mn4+ ions (S = 3/2, І = 5/2) were found. The Mn2+ EPR signals are proposed as structural probes in manganese-doped magnesium titanate ceramics.

Photocatalytic degradation of tetracycline hydrochloride with visible light-responsive bismuth tungstate/conjugated microporous polymer

• The construction of Bi 2 WO 6 /CMPs composite with Sonogashira-Hagihara polymerization. • The optimized tetracycline hydrochloride degradation efficiency reached 84 %. • The interfacial heterojunction of composite facilitates the separation of e − and h + . Conjugated microporous polymer (CMP) is an emerging organic semiconductor with π-conjugated skeletons, and the bandgap of CMP can be flexibly modulated to harvest visible light. Based on the diversity and adjustability of monomers in CMP, we designed and synthesized donor-accepter (D-A) type BTN-CMP through Sonogashira-Hagihara cross-coupling polymerization, further in-situ constructing series of inorganic/organic Z-scheme BW/BTN- n composite in the presence of Bi 2 WO 6 . After optimization, the tetracycline hydrochloride ( C 0 = 10 mg·L −1 ) degradation efficiency reached 84% with BW/BTN-2 as catalyst in 90 min under visible light irradiation, the apparent rate constant k 1 is 0.017 min −1 , which is 1.7 and 5.7 times higher than bare Bi 2 WO 6 and BTN-CMP. X-ray photoelectron spectra and UV–Vis diffuse spectra showed that the enhanced photocatalytic activity originated from the tight heterojunction between Bi 2 WO 6 and BTN-CMP, which can extend the light absorption range and facilitate the separation and transport of photogenerated charges in the interface of heterojunction. The active species trapping experiments and electron spin resonance technique revealed that h + was the dominant active species during the photodegradation process of tetracycline hydrochloride (TCH). The present study demonstrated the feasibility to construct inorganic/organic composite for the photocatalytic degradation of environmental pollutants.

Ultrafast photodegradation of nitenpyram by Ag/Ag3PO4/Zn–Al LDH composites activated by persulfate system: Removal efficiency, degradation pathway and reaction mechanism

In this study, an investigation is conducted into the degradation of nitenpyram (NTP) using highly efficient APMMO/PDS/Vis system. As photocatalysts, silver phosphate (AP) and calcined Zn–Al layered double hydroxides (MMO) exhibit high efficiency in achieving charge separation. Besides, the injection of electrons into peroxydisulfate (PDS) from the APMMO can contribute to obtaining the species in the active state with higher efficiency. Based on the APMMO/PDS/Vis system, 50 mg/L of nitenpyram (NTP, 50 mL) can be completely removed in 60 min using 0.8 g/L photocatalyst and 0.2 g/L PDS under the optimum condition and visible light (780 nm > λ > 420 nm). Meanwhile, as demonstrated under visible light within 30 min, an ultrahigh degradation efficiency can be achieved by NTP based on APMMO1/PDS/Vis system. Besides, the electron paramagnetic resonance (EPR) technique and radical quenching experiments suggested 1O2, h+, SO4−•, •O2−, and •OH are all contributory to the removal of pollutants. Given the outcomes achieved by LC/MS system and mass spectrometry, the primary degradation intermediates of NTP end up being converted into photodegradation products (such as 2-Chloropyridine, 6-Chloropurine Riboside and dl-Leucine). Additionally, there are three potential photodegradation pathways to NTP degradation have been deployed. Moreover, the NTP light degradation occurring in APMMO1/PDS/Vis system is competent under the three types of real water sample. Accordingly, the high-efficiency APMMO1/PDS/Vis system is fit for use in water pollution control for agricultural productions.

Sustainable micro-activation of dissolved oxygen driving pollutant conversion on Mo-enhanced zinc sulfide surface in natural conditions

The activation of inert oxygen (O2) often consumes enormous amounts of energy and resources, which is a global challenge in the field of environmental remediation and fuel cells. Organic pollutants are abundant in electrons and are promising alternative electron donors. Herein, we implement sustainable microactivation of dissolved oxygen (DO) by using the electrons and adsorption energy of pollutants by creating a nonequilibrium microsurface on nanoparticle-integrated molybdenum (Mo) lattice-doped zinc sulfide (ZnS) composites (MZS-1). Organic pollutants were quickly removed by DO microactivation in the MZS-1 system under natural conditions without any additional energy or electron donor. The turnover frequency (TOF, per Mo atom basis) is 5 orders of magnitude higher than those of homogeneous systems. Structural and electronic characterization technologies reveal the change in the crystalline phase (Zn-S-Mo) and the activation of π-electrons on six-membered rings of ZnS after Mo doping, which results in the formation of a nonequilibrium microsurface on MZS-1. This is the key for the strong interfacial interaction and directional electron transfer from pollutants to MZS-1 through the delocalized π-π conjugation effect and from MZS-1 to DO via Zn-S-Mo, as demonstrated by electron paramagnetic resonance (EPR) techniques and density functional theory (DFT) calculations. This process achieves the efficient use of pollutants and the low-energy activation of O2 through the construction of a nonequilibrium microsurface, which shows new significance for water treatment.

Electron spin dynamics in sucrose-derived luminescent carbon dot-silica nanocomposites

In the present work, a bottom-up approach to synthesize luminescent carbon dot-silica (CDs@SiO2) nanocomposites from the sucrose precursor was utilized. The sucrose concentration and thermal treatment effect on electron spin dynamics in CDs@SiO2 nanocomposites was investigated by electron spin resonance (ESR) technique. A single ESR line resulting from exchange interaction between localized and non-localized electrons was observed. The non-localized electrons were related to carbon-related radicals in the sp3-hybridized state, while the carbon dots (CDs) act as localized electrons. The observed narrowing of the exchange ESR line with temperature rise was explained by a combination of Anderson's spin-exchange motional narrowing and a hopping wave function. The high conductivity of the material is evidenced by the Dysonian lineshape of the ESR signal. The relation between CDs size and conductivity of the CDs@SiO2 nanocomposites was found. The metallic character of the CDs@SiO2 conductivity was explained by the quantum size effect that occurred due to the reaggregation of the CDs. It was concluded that the previously observed shift of photoluminescence (PL) band and further quenching of PL with the increase of sucrose concentration in CDs@SiO2 is caused by the quantum size effect.

Photocatalytic Oxidation of Acid Orange 10 dye Molecules using Cerium Oxide Nanosphere Particles under Ultraviolet and Visible Light Irradiations

Exploration of semiconductors in the field of photocatalysis plays a crucial role in energy and environmental remediation in particular oxidation/reduction of toxic organic contaminants from water and wastewater. The present research work aims on synthesis of pristine CeO2nanoparticles by precipitation method and was thoroughly characterized by Fourier Transform Infrared spectroscopy, X-ray Diffraction, UV-vis-Diffuse Reflectance Spectroscopy, High Resolution Scanning Electron Microscopy, EDAX and Electron Spin Resonance techniques. The band gap energy (Ebg) was found to be 3.19 eV. The synthesized nanomaterials showed spherical morphology and the particles size ranged from 50-93 nm. The insitu generation of ·OH radicals was confirmed from ESR studies. The synthesized CeO2nanospheres was evaluatedin photocatalytic oxidation of an azo dye Acid orange 10 under Ultraviolet and visible light irradiations. Experimental studies such as pH, catalyst amount and effect of initial dye concentration were also studied. Kinetic studies indicate the photo reaction follows pseudo-first order rate equation. The photocatalytic oxidation of dye molecules were monitored by UV-visible spectroscopy and COD analyses. The level of chemical oxygen demand (COD) of the photodegraded samples decreases in both the photocatalytic systems indicating that dye molecules readily degraded under present experimental conditions.Effect of electrolytes like MgSO4,KCl, Na2CO3 and NaHCO3 were also investigated to check interference of inorganic anions on photocatalytic oxidation of dye molecules using CeO2 nanospheres. Finally, the prepared catalyst was checked for its reusability and the photocatalyst exhibited better photocatalytic activity evenafter three cycles of regeneration.Copyright © VBRI Press.

Persulfate enhanced electrochemical oxidation of phenol with CuFe2O4/ACF (activated carbon fibers) cathode

Phenol wastewater is threatened to human living environment and should been treated carefully before discharging into the environment. For my research, electrochemical (EC) oxidation of phenol using CuFe2O4/ACF cathode and mixed metal oxide (RuO2/Ti) anodes was investigated. In order to increase the EC oxidation efficiency of phenol, persulfate (PS) was added into the EC system. Various systems including EC-1 oxidation (RuO2/Ti cathode and RuO2/Ti anode), EC-2 oxidation (ACF cathode and RuO2/Ti anode), EC-3 oxidation (ACF cathode and RuO2/Ti anode, adding CuFe2O4 particle), PS oxidation (only adding PS) and EC/PS oxidation (CuFe2O4/ACF cathode and RuO2/Ti anode, adding PS) for phenol removal were compared, and the removal efficiency of phenol was determined to be 19%, 25%, 46%, 43 and 85%, respectively. Effects of K2S2O8 concentration, current density and initial pH on the removal efficiency of phenol were analyzed. The optimal phenol removal efficiency (97%) was achieved after 60 min reaction under conditions: PS concentration of 1.00 mM, current density of 50 A/m2, and initial pH of 7.0. The generation of reactive oxidant species in solution was confirmed by the electron spin resonance technique, which was in accord with the radical quenching experiments results, indicating that oxidation of phenol was assigned to radical oxidation and non-radical oxidation processes.

The promotion effect of iron to Cu/ZSM‐5 catalyst for NOx removal by NH3‐SCR

AbstractThe Cu/ZSM‐5 and Cu‐Fe/ZSM‐5 catalysts (ZSM‐5 with Si:Al ratio of 25:1) were created utilizing the liquid ion‐exchange technique. The effects of Fe on the physical and chemical characteristics of Cu/ZSM‐5 catalysts were investigated using X‐ray diffraction, field‐emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, nitrogen adsorption/desorption, and temperature‐programmed ammonia desorption. The coordination and valence state of copper and iron elements at intersections or in channels of ZSM‐5 was determined by the electron paramagnetic resonance technique. The effects of metal doping on the structure and catalytic activity of all catalysts were comprehensively investigated for NOx removal utilizing selective catalytic reduction with ammonia (NH3‐SCR). The results indicated that the promotion of iron significantly increased the NOx conversion and N2 selectivity of the Cu/ZSM‐5 catalyst for NH3‐SCR in the temperature range from 200 to 600 °C, and catalysts were highly resistant to high space velocity. This article describes a simple and uncomplicated method for synthesizing the commercially viable catalyst used in NH3‐SCR technology to reduce NOx emissions.

A multifunctional manipulation to stabilize oxygen redox and phase transition in 4.6 V high-voltage LiCoO2 with sXAS and EPR studies

LiCoO2, as a domain cathode material of Li-ion batteries, faces a great deal of challenges due to the limited cycling stability at high voltage (>4.35 V vs. Li/Li+). These issues are tentatively addressed here by a multifunctional self-stabilization modification strategy, involving trace Mg bulk doping, surface gradient Ti doping and BaTiO3 dot coating in LiCoO2. The multifunctional synergy is verified to overcome the detrimental irreversible phase transition and the growth of impedance of LiCoO2 cycling at 4.6 V. By using soft X-ray absorption spectroscopy (sXAS) and electron paramagnetic resonance (EPR) techniques, we also elucidate that Ti surface gradient doping can reinforce the structure rigidity of the particles while significantly attenuates the irreversible oxygen redox at high voltage. All these strategies promote the prolonged cyclic performance of LiCoO2 under 4.6 V high-voltage through different mechanism. This elaborate investigation provides an instructive contribution in the advancement of high-voltage LiCoO2.

Time-Resolved EPR Revealed the Formation, Structure, and Reactivity of N-Centered Radicals in an Electrochemical C(sp3)-H Arylation Reaction.

Electrochemical synthesis has been rapidly developed over the past few years, while a vast majority of the reactions proceed through a radical pathway. Understanding the properties of radical intermediates is crucial in the mechanistic study of electrochemical transformations and will be beneficial for developing new reactions. Nevertheless, it is rather difficult to determine the "live" radical intermediates due to their high reactivity. In this work, the formation and structure of sulfonamide N-centered radicals have been researched directly by using the time-resolved electron paramagnetic resonance (EPR) technique under electrochemical conditions. Supported by the EPR results, the reactivity of N-centered radicals as a mediator in the hydrogen atom transfer (HAT) approach has been discussed. Subsequently, these mechanistic study results have been successfully utilized in the discovery of an unactivated C(sp3)-H arylation reaction. The kinetic experiments have revealed the rate-determined step is the anodic oxidation of sulfonamides.

PHASE TRANSITION STUDIES OF CHOLESTERYL PALMITATE, CHOLESTERYL DECANOATE AND THEIR MIXTURES USING DIELECTRIC, EPR AND DTA TECHNIQUES

The phase transition of two liquid crystalline materials, namely cholesteryl palmitate and cholesteryl decanoate and their mixtures (by weight)are studied using dielectric, Electron paramagnetic resonance (EPR) and differential thermal analysis (DTA) techniques. From the dielectric measurements, the phase transition temperatures were determined from the discontinuities in the curve between dielectric constant and temperatures for all the samples investigated. Further, since mixing of two liquid crystals modifies the transition of phases, the measurements were carried out on the mixtures of the two liquid crystals. Order parameter for each sample was calculated at varying temperatures by measuring the hyperfine splitting of three line EPR spectrums. The discontinuities in the curve between order parameter and the temperature again indicated the phase transition of the liquid crystals and their mixtures. A DTA study on these samples was also carried out in order to probe further their transitional behaviour. The DTA records of both the liquid crystals and their mixtures support the transition behaviour observed from the dielectric and EPR measurements.

Potentials of intravenous laser blood irradiation to correct peroxidation and antioxidant activity as a result of surgical distress

Purpose: to reveal protective effects of intravenous low-level laser blood irradiation (ILBI) during surgical interventions at the gallbladder as well as to study the state of antioxidant activity, lipid peroxidation and endogenous intoxication.Material and methods. In the perioperative period, 40 patients from the main group (I) had traditional treatment which included pharmacological preparations and sessions of intravenous laser blood irradiation. 45 patients from the control group (II) had only traditional (pharmacotherapeutic) treatment. In both groups during surgery, the anesthetic protection consisted of classical neuroleptanalgesia. The age of patients in both groups did not differ significantly. Intravenous laser blood irradiation was done with helium-neon laser “Atoll” 632 nm (Fokon Ltd, St-Petersburg, Russia). During surgery, three irradiation sessions were performed at radiation power of 20 mW and exposure 15 minutes at various stages of surgery: 30 minutes before induction of anesthesia, at the traumatic stage and 30 minutes before the expected finish of the surgery. Ceruloplasmin and transferrin levels in the blood plasma were assessed with the electron paramagnetic resonance technique. The ratio of ceruloplasmin/transferrin which characterizes the level of antioxidant activity was also established. The level of endogenous intoxication was assessed using the previously published technique. The quantitative characteristics of endogenous intoxication by this technique is the value of optical density (D280) and total optical density of components related to high molecular weight and low molecular weight fractions.Results. ILBI sessions in patients neutralize changes in the level of ceruloplasmin and transferrin in blood. The data obtained also confirm ILBI protective effects at protein SH-groups or activation of the restoration of protein SH-groups that were damaged by oxidation as a result of surgical aggression and trauma.Conclusion. The protective effect of intravenous laser blood irradiation in addition to the standard preoperative therapy optimizes pharmacological anesthetic protection during surgery under the existing traditional schemes of combined general anesthesia.

Enhanced peroxymonosulfate activation by hierarchical porous Fe3O4/Co3S4 nanosheets for efficient elimination of rhodamine B: Mechanisms, degradation pathways and toxicological analysis

Fenton-like catalysts have usually superior catalytic activities, however, some drawbacks of ion leaching and difficult-to-recovery limit their applications. In this work, a hierarchical porous Fe3O4/Co3S4 catalyst was fabricated via a simple phase change reaction to overcome these shortcomings. The introduced iron cooperates with cobalt achieving high-efficiency activation of peroxymonosulfate (PMS) to eliminate Rhodamine B (RhB). The results showed that 0.05 g/L Fe3O4/Co3S4 and 1 mM PMS could quickly remove 100% of 200 mg/L RhB within 20 min, and the removal rate of RhB remained above 82% after 5 cycles. Moreover, the as-prepared Fe3O4/Co3S4 possessed a great magnetic separation capacity and good stability of low metal leaching dose. Radical quenching experiments and electron paramagnetic resonance (EPR) techniques proved that sulfate radicals (SO4•−) were the dominant reactive oxygen species responding for RhB degradation. X-ray photoelectron spectroscopy (XPS) pointed out that the synergism of sulfur promoted the cycling of Co3+/Co2+ and Fe3+/Fe2+, boosting the electron transfer between Fe3O4/Co3S4 and PMS. Moreover, the degradation pathways of RhB were deduced by combining liquid chromatography-mass spectrometry (LC-MS) analysis and density functional theory (DFT) calculations. The toxicities of RhB and its intermediates were evaluated as well, which provided significant assistance in the exploration of their ecological risks.

Investigation on lead-free Mn-doped Cs2NaInCl6 double perovskite phosphors and their optical properties

Doping with transition metal ions in lead-free double perovskite material of Cs2NaInCl6 has been highly spotlighted for tailoring optical properties and advancing light-emitting applications. Herein, solvothermal method is employed to synthesizing Mn-doped Cs2NaInCl6 phosphors with a purpose of imparting new optical properties in the visible light region. X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, thermogravimetric analysis, electron paramagnetic resonance and photoluminescence (PL) techniques confirm that Mn-doped Cs2NaInCl6 exhibits stable double perovskite crystal structure, good stability, and exceptional electronic properties. Mn-doped Cs2NaInCl6 also shows observable red fluorescence peaking at 610 nm with PL decay lifetime of about 0.21 ms and PL quantum yield of about 5%, owing to the 4T1→6A1 transition of the Mn d electron.

Dense radical formation in L-alanine-3,3,3-d3 and L-alanine-d4 by 1.5 keV soft X-ray irradiation

Radicals produced in crystalline L-alanine-3,3,3-d3 and L-alanine-d4 were observed by the electron spin resonance (ESR) technique during 1.5 keV soft X-ray irradiation. The spectral change from •CHCD3COOH to •CDCD3COOH by a hydrogen exchange reaction was directly observed in L-alanine-3,3,3-d3. The line width of the ESR spectra obtained by the soft X-ray irradiation was 1.5 times wider than that of hard X-rays from a previous report, meaning a higher density of radicals. The efficiency of the radical yield by the soft X-ray irradiation was 10−6 relative to that by γ-irradiation. The product formed by the radical recombination was observed by an LC/MS analysis. For the soft X-ray irradiation, many radicals will be lost by the efficient radical-radical recombination due to the higher density of the radicals, just as the high-LET irradiation by heavy ions. The result was the same as the yield of hydroxyl radicals in an aqueous solution that decreased with the decreasing photon energy from 1.25 MeV to 1.5 keV. We concluded that the high LET nature of the lower energy photons leads to the dense radical formation in the crystalline alanine powder.