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Nanomaterials (Basel, Switzerland) Jun 2024Ultra-small magnetic FeO nanoparticles are successfully synthesized in basic solutions by using the radiolytic method of the partial reduction in Fe in the presence of...
Ultra-small magnetic FeO nanoparticles are successfully synthesized in basic solutions by using the radiolytic method of the partial reduction in Fe in the presence of poly-acrylate (PA), or by using the coprecipitation method of Fe and Fe salts in the presence of PA. The optical, structural, and magnetic properties of the nanoparticles were examined using UV-Vis absorption spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and SQUID magnetization measurements. The HRTEM and XRD analysis confirmed the formation of ultra-small magnetite nanoparticles in a spinel structure, with a smaller size for radiation-induced particles coated by PA (5.2 nm) than for coprecipitated PA-coated nanoparticles (11 nm). From magnetization measurements, it is shown that the nanoparticles are superparamagnetic at room temperature. The magnetization saturation value = 50.1 A m kg of radiation-induced nanoparticles at 60 kGy is higher than = 18.2 A m kg for coprecipitated nanoparticles. Both values are compared with nanoparticles coated with other stabilizers in the literature.
PubMed: 38921891
DOI: 10.3390/nano14121015 -
Advanced Science (Weinheim,... Jun 2024The 2-bit Lindqvist-type polyoxometalate (POM) [VO((OCH)CCHN)] with a diamagnetic {VO} core and azide termini shows six fully oxidized V centers in solution as well as...
The 2-bit Lindqvist-type polyoxometalate (POM) [VO((OCH)CCHN)] with a diamagnetic {VO} core and azide termini shows six fully oxidized V centers in solution as well as the solid state, according to V NMR spectroscopy. Under UV irradiation, it exhibits reversible switching between its ground S state and the energetically higher lying states in acetonitrile and water solutions. TD-DFT calculations demonstrate that this process is mainly initialized by excitation from the S to S state. Pulse radiolysis transient absorption spectroscopy experiments with a solvated electron point out photochemically induced charge disproportionation of V into V and electron communication between the POM molecules via their excited states. The existence of this unique POM-to-POM electron communication is also indicated by X-ray photoelectron spectroscopy (XPS) studies on gold-metalized silicon wafers (Au//SiO//Si) under ambient conditions. The amount of reduced vanadium centers in the "confined" environment increases substantially after beam irradiation with soft X-rays compared to non-irradiated samples. The excited state of one POM anion seems to give rise to subsequent electron transfer from another POM anion. However, this reaction is prohibited as soon as the relaxed T state of the POM is reached.
PubMed: 38868906
DOI: 10.1002/advs.202401595 -
Chemphyschem : a European Journal of... May 2024Photocatalysis using transition-metal complexes is widely considered the future of effective and affordable clean-air technology. In particular, redox-stable, easily...
Photocatalysis using transition-metal complexes is widely considered the future of effective and affordable clean-air technology. In particular, redox-stable, easily accessible ligands are decisive. Here, we report a straightforward and facile synthesis of a new highly stable 2,6-bis(triazolyl)pyridine ligand, containing a nitrile moiety as a masked anchoring group, using copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction. The reported structure mimics the binding motif of uneasy to synthesize ligands. Pulse radiolysis under oxidizing and reducing conditions provided evidence for the high stability of the formed radical cation and radical anion 2,6-di(1,2,3-triazol-1-yl)-pyridine compound, thus indicating the feasibility of utilizing this as a ligand for redox active metal complexes and the sensitization of metal-oxide semiconductors (e.g., TiO2 nanoparticles or nanotubes).
PubMed: 38819992
DOI: 10.1002/cphc.202400273 -
Dalton Transactions (Cambridge, England... Jun 2024First-of-a-kind temperature-controlled electron pulse radiolysis experiments facilitated the radiation-induced formation of Am(IV) in concentrated (6.0 M) HNO, and...
First-of-a-kind temperature-controlled electron pulse radiolysis experiments facilitated the radiation-induced formation of Am(IV) in concentrated (6.0 M) HNO, and enabled the derivation of Arrhenius and Eyring activation parameters for instigating the radical reaction between NO˙ and Am(III).
PubMed: 38776119
DOI: 10.1039/d4dt00991f -
Environmental Science & Technology May 2024Photoexcitation of sulfite (SO) is often used to generate hydrated electrons (e) in processes to degrade perfluoroalkyl and polyfluoroalkyl substances (PFASs)....
Photoexcitation of sulfite (SO) is often used to generate hydrated electrons (e) in processes to degrade perfluoroalkyl and polyfluoroalkyl substances (PFASs). Conventional consensus discourages the utilization of SO concentrations exceeding 10 mM for effective defluorination. This has hindered our understanding of SO chemistry beyond its electron photogeneration properties. In contrast, the radiation-chemical study presented here, directly producing e through water radiolysis, suggests that SO plays a previously overlooked activation role in the defluorination. Quantitative Co gamma irradiation experiments indicate that the increased SO concentration from 0.1 to 1 M enhances the defluorination rate by a remarkable 15-fold, especially for short-chain perfluoroalkyl sulfonate (PFSA). Furthermore, during the treatment of long-chain PFSA (CF-SO) with a higher concentration of SO, the intermediates of CH-SO and CF-COO were observed, which are absent without SO. These observations highlight that a higher concentration of SO facilitates both reaction pathways: chain shortening and H/F exchange. Pulse radiolysis measurements show that elevated SO concentrations accelerate the bimolecular reaction between e and PFSA by 2 orders of magnitude. F NMR measurements and theoretical simulations reveal the noncovalent interactions between SO and F atoms, which exceptionally reduce the C-F bond dissociation energy by nearly 40%. As a result, our study offers a more effective strategy for degrading highly persistent PFSA contaminants.
Topics: Sulfites; Electrons; Fluorocarbons; Water
PubMed: 38747404
DOI: 10.1021/acs.est.4c01444 -
The Journal of Physical Chemistry. C,... Apr 2024A series of steady-state and time-resolved spectroscopies were performed on a set of eight carbene-metal-amide (cMa) complexes, where M = Cu and Au, that have been used...
A series of steady-state and time-resolved spectroscopies were performed on a set of eight carbene-metal-amide (cMa) complexes, where M = Cu and Au, that have been used as photosensitizers for photosensitized electrocatalytic reactions. Using ps-to-ns and ns-to-ms transient absorption spectroscopies (psTA and nsTA, respectively), the excited-state kinetics from light absorption, intersystem crossing (ISC), and eventually intermolecular charge transfer were thoroughly characterized. Using time-correlated single photon counting (TCSPC) and psTA with a thermally activated delayed fluorescence (TADF) model, the variation in intersystem crossing (ISC), ( → ) rates (∼3-120 × 10 s), and Δ values (73-115 meV) for these compounds were fully characterized, reflecting systematic changes to the carbene, carbazole, and metal. The psTA additionally revealed an early time relaxation (rate ∼0.2-0.8 × 10 s) attributed to solvent relaxation and vibrational cooling. The nsTA experiments for a gold-based cMa complex demonstrated efficient intermolecular charge transfer from the excited cMa to an electron acceptor. Pulse radiolysis and bulk electrolysis experiments allowed us to identify the character of the transient excited states as ligand-ligand charge transfer as well as the spectroscopic signature of oxidized and reduced forms of the cMa photosensitizer.
PubMed: 38690534
DOI: 10.1021/acs.jpcc.4c01994 -
The Journal of Physical Chemistry. B May 2024The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with...
The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with time-resolved spectrophotometry. The initially observed absorption spectrum upon oxidation of DNA by the selenite radical is consistent with spin on cytosine (C), as the GC pair neutral radical, followed by the spectra of oxidized ligands. The rate of oxidation of bound ligands increased with an increase in the ratio () ligands per base pair from 0.005 to 0.04. Both the rate of ligand oxidation and the estimated range of hole transfer (up to 30 DNA base pairs) decrease with the decrease in one-electron reduction potential between the GC pair neutral radical of ca. 1.54 V and that of the ligand radicals (', 0.90-0.99 V). Linear plots of log of the rate of hole transfer versus give a common intercept at = 0 and a free energy change of 12.2 ± 0.3 kcal mol, ascribed to the GC pair neutral radical undergoing a structural change, which is in competition to the observed hole transfer along DNA. The rate of hole transfer to the ligands at distance, , from the GC pair radical, , is described by the relationship = exp(constant/), where includes the rate constant for surmounting a small barrier.
Topics: DNA; Base Pairing; Free Radicals; Oxidation-Reduction; Benzimidazoles; Animals; Cattle; Ligands; Bisbenzimidazole; DNA Repair; DNA Damage; Cytosine
PubMed: 38686959
DOI: 10.1021/acs.jpcb.4c01069 -
Chemosphere May 2024The paper presents the results of studying the efficiency of the bisphenol A transformation in water exposed to ultraviolet radiation and a high-energy-pulse-electron...
The paper presents the results of studying the efficiency of the bisphenol A transformation in water exposed to ultraviolet radiation and a high-energy-pulse-electron beam (e-beam). It has been shown that in both cases, degradation of dissolved bisphenol A occurs, accompanied by an increase in the absorption coefficient in the wavelength region of more than 300 nm. After exposure, products were recorded that fluoresced in the region of more than λ = 400 nm. The fluorescent transformation product of bisphenol A in water (λ = 425 nm) was maximum formatted after an KrCl excilamp irradiated, and under the action of an e-beam, the accumulation of this product was minimal. Under e-beam radiation (170 keV) the efficiency of bisphenol A (1 mM) removal reached 97%. The data obtained allow us to develop ideas about photolysis and radiolysis in natural water systems when knowledge about targeted and optimal conditions for the degradation of bisphenol A is needed.
Topics: Benzhydryl Compounds; Phenols; Ultraviolet Rays; Photolysis; Water Pollutants, Chemical; Electrons; Water Purification
PubMed: 38556183
DOI: 10.1016/j.chemosphere.2024.141802 -
Physical Chemistry Chemical Physics :... Apr 2024Picosecond pulse radiolysis measurements were employed to assess the effectiveness of N in scavenging quasi-free electrons in aqueous solutions. The absorption spectra...
Picosecond pulse radiolysis measurements were employed to assess the effectiveness of N in scavenging quasi-free electrons in aqueous solutions. The absorption spectra of hydrated electrons were recorded within a 100 ps timeframe across four distinct solutions with N concentrations of 0.5, 1, 2, and 5 M in water. The results revealed a concentration-dependent shift in the maximum absorption spectra of fully solvated electrons. Notably, at 5 M concentration, the maximum absorption occurred at 670 nm, in contrast to 715 nm observed for water. Intriguingly, the formation yield of hydrated electrons within the initial 5 ps electron pulse remained unaffected, showing that, even at a concentration of 5 M, N does not effectively scavenge quasi-free electrons. This is in disagreement with conclusions from stochastic models found in the literature. This observation has an important impact on understanding the mechanism of H formation in water radiolysis, which we discuss briefly here.
PubMed: 38545925
DOI: 10.1039/d4cp00157e -
Dalton Transactions (Cambridge, England... Apr 2024A systematic study of the impact on the chemical reactivity of the oxidising -dodecane radical cation (RH˙) with -element complexed 2-ethylhexylphosphonic acid...
A systematic study of the impact on the chemical reactivity of the oxidising -dodecane radical cation (RH˙) with -element complexed 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) has been undertaken utilizing time-resolved electron pulse radiolysis/transient absorption spectroscopy and high-level quantum mechanical calculations. Lanthanide ion complexed species, [Ln((HEH[EHP]))], exhibited vastly increased reactivity (over 10× faster) in comparison to the non-complexed ligand in -dodecane solvent, whose rate coefficient was = (4.66 ± 0.22) × 10 M s. Similar reactivity enhancement was also observed for the corresponding americium ion complex, = (5.58 ± 0.30) × 10 M s. The vastly increased reactivity of these -element complexes was not due to simple increased diffusion-control of these reactions; rather, enhanced hole transfer mechanisms for the complexes were calculated to become energetically more favourable. Interestingly, the observed reactivity trend with lanthanide ion size was not linear; instead, the rate coefficients showed an initial increase (Lu to Yb) followed by a decrease (Tm to Ho), followed by another increase (Dy to La). This behaviour was excellently predicted by the calculated reaction volumes of these complexes. Complementary cobalt-60 gamma irradiations for select lanthanide complexes demonstrated that the measured kinetic differences translated to increased ligand degradation at steady-state timescales, affording ∼38% increase in ligand loss of a 1 : 1 [La((HEH[EHP]))] : HEH[EHP] ratio system.
PubMed: 38407412
DOI: 10.1039/d4dt00424h