A variety of dimensional-structured nanocarbons were applied for the first time as metal-free catalysts to activate persulfate (PS) for catalytic oxidation of phenolics and dyes as well as their ...degradation intermediates. Single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO), and mesoporous carbon (CMK-8) demonstrated superior catalytic activities for heterogeneous PS activation, whereas fullerene (C60), nanodiamonds, and graphitic carbon nitride (g-C3N4) presented low efficiencies. Moreover, the carbocatalysts presented even better catalytic performances than activated carbon and metal oxides, such as Fe3O4, CuO, Co3O4, and MnO2. The activity of prepared rGO-900 was further competing to the most efficient electron donor of zerovalent iron (ZVI). Both characterization and oxidation results suggested that the catalytic performances of the nanocarbons are determined by the intrinsic atom arrangements of carbon hybridization, pore structure, defective sites, and functional groups (especially the carbonyl groups). Electron paramagnetic resonance (EPR) spectra revealed that carbocatalysts might act as an excellent electron bridge in activation of PS to oxidize adsorbed water directly to generate hydroxyl radicals, distinct from homogeneous and metal-based catalytic activation. This study discovers several efficient nanocarbons for heterogeneous PS activation, and it presents new insights into the catalytic activation processes, providing a fascinating strategy to develop metal-free catalysts for green remediation.
Implementation and applications of shaped pulses in EPR Endeward, Burkhard; Bretschneider, Matthias; Trenkler, Paul ...
Progress in nuclear magnetic resonance spectroscopy,
August-October 2023, 2023-08-00, 20230801, Letnik:
136-137
Journal Article
Recenzirano
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•Shaped pulses created by AWG improved pulse EPR experiments.•Gain in inversion and excitation bandwidth by shaped pulses in EPR.•Description of implementation of AWGs into EPR ...spectrometer.•Testing and optimization procedures of AWG shaped pulses in EPR.•Applications of shaped pulses in dipolar and hyperfine EPR spectroscopy.
In this review, we describe the application of shaped pulses for EPR spectroscopy. Pulses generated by fast arbitrary waveform generators are mostly used in the field of EPR spectroscopy for broadband (200 MHz-1 GHz) excitation of paramagnetic species. The implementation and optimization of such broadband pulses in existing EPR spectrometers, often designed and optimized for short rectangular microwave pulses, is demanding. Therefore, a major part of this review will describe in detail the implementation, testing and optimization of shaped pulses in existing EPR spectrometers. Additionally, we review applications using such pulses for broadband inversion of longitudinal magnetization as well as for the creation and manipulation of transverse magnetization in the field of dipolar and hyperfine EPR spectroscopy. They demonstrate the great potential of shaped pulses to improve the performance of pulsed EPR experiments. We give a brief theoretical description of shaped pulses and their limitations, especially for adiabatic pulses, most often used in EPR. We believe that this review can on the one hand be of practical use to EPR groups starting to work with such pulses, and on the other hand give readers an overview of the state of the art of shaped pulse applications in EPR spectroscopy.
While natural photosynthesis serves as the model system for efficient charge separation and decoupling of redox reactions, bio‐inspired artificial systems typically lack applicability owing to ...synthetic challenges and structural complexity. We present herein a simple and inexpensive system that, under solar irradiation, forms highly reductive radicals in the presence of an electron donor, with lifetimes exceeding the diurnal cycle. This radical species is formed within a cyanamide‐functionalized polymeric network of heptazine units and can give off its trapped electrons in the dark to yield H2, triggered by a co‐catalyst, thus enabling the temporal decoupling of the light and dark reactions of photocatalytic hydrogen production through the radical′s longevity. The system introduced here thus demonstrates a new approach for storing sunlight as long‐lived radicals, and provides the structural basis for designing photocatalysts with long‐lived photo‐induced states.
Live long and prosper: A cyanamide‐functionalized carbon nitride can form ultra‐long‐lived radicals under solar irradiation in the presence of an electron donor. This longevity enables the temporal decoupling of the two half reactions in the photo‐redox production of hydrogen.
Following its discovery more than 30 years ago, the enhanced permeability and retention (EPR) effect has become the guiding principle for cancer nanomedicine development. Over the years, the ...tumor-targeted drug delivery field has made significant progress, as evidenced by the approval of several nanomedicinal anticancer drugs. Recently, however, the existence and the extent of the EPR effect - particularly in patients - have become the focus of intense debate. This is partially due to the disbalance between the huge number of preclinical cancer nanomedicine papers and relatively small number of cancer nanomedicine drug products reaching the market. To move the field forward, we have to improve our understanding of the EPR effect, of its cancer type-specific pathophysiology, of nanomedicine interactions with the heterogeneous tumor microenvironment, of nanomedicine behavior in the body, and of translational aspects that specifically complicate nanomedicinal drug development. In this virtual special issue, 24 research articles and reviews discussing different aspects of the EPR effect and cancer nanomedicine are collected, together providing a comprehensive and complete overview of the current state-of-the-art and future directions in tumor-targeted drug delivery.
•Glasses are prepared by melt quenching method.•XRD confirmed the amorphous nature.•EPR spectra revealed the resonance peaks at g=4.2, 3.2 and 2.0.•The bond between Mn2+ ion and its ligands is ...Ionic.•Increase of NaF/KF increases the tetrahedral BO4 units.
The glass systems with the composition xMF-(40-x) CdO-59.5B2O3, (M=Na, K and x= 5, 10, 15, 20, 25, 30 and 35 mol %) doped with 0.5 mol % of MnO2 were prepared using the melt quenching method. The glasses were analysed using XRD, UV-VIS, EPR and FTIR spectra. The optical band gap (Eg) values of the glass systems were observed to increase from 3.21 eV NFCBM1 to 3.48 eV NFCBM7 and 2.56eV KFCBM1 to 3.31 eV KFCBM7 with increase of NaF/KF concentration which may be due to decreasing of the number of non bridging oxygens. The (Δg) values suggest the presence of Mn2+ ions in octahedrally coordinated complex and the A values suggest that the bond between Mn2+ ions and its ligand filed is ionic. The BO4 atoms were increased in both NaF and KF containing glasses with increase in NaF/KF concentration.
Cu bound to Aβ (heads of the meteorites) produces reactive oxygen species (tails) that attack the brain. In the presence of the azamacrocyclic ligand 3N1S (the green belt), the Cu ions are removed by ...the ligand (the head of the meteorite is broken) and the ROS production is abolished (the tail disappears). Hence, the brain is safe behind its shield. In absence of 3N1S, the ROS produced by Cu(Aβ) attack the brain, which is “destroyed”. More information can be found in the Research Article by C. Esmieu, C. Hureau, and co‐workers (DOI: 10.1002/chem.202203667).
Carbon nitride (CN) is a heterogeneous photocatalyst that combines good structural properties and a broad scope. The photocatalytic efficiency of CN is associated with the presence of defective and ...radical species. An accurate description of defective states—both at a local and extended level—is key to develop a thorough mechanistic understanding of the photophysics of CN. In turn, this will maximise the generation and usage of photogenerated charge carriers and minimise wasteful charge recombination. Here the influence of morphology and light‐excitation on the number and chemical nature of radical defects is assessed. By exploiting the magnetic dipole‐dipole coupling, the spatial distribution of native radicals in CN is derived with high precision. From the analysis an average distance in the range 1.99–2.34 nm is determined, which corresponds to pairs of radicals located approximately four tri‐s‐triazine units apart.
Radicals in carbon nitride are invoked as photocatalytically competent species. However, their structure and localisation is ill‐defined. Here we provide a quantitative assessment of speciation, electronic structure, long‐range distributions and photo‐response of such radicals, as a function of carbon nitride morphology. This work paves the way to the engineering of the defective structure of carbon nitride and related 2D materials.
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•An approach to predict the optimal Hubbard Ueff value used in DFT+U is proposed.•Optimize the Ueff for Li2MnO3 by comparing these calculated Fermi-contact shifts.•Finding optimal ...Ueff helps calculate SS-NMR parameters and material properties.
The isotropic chemical shifts can be calculated by hybrid functionals, which costs lots of computational resources. To save time, DFT+U could be employed to calculate the isotropic chemical shifts. However, the calculated properties are very sensitive to the Hubbard correction value Ueff. Here the double Fermi-contact-shift verification approach with DFT+U method is proposed with much higher computational efficiency, that is, concurrently calculate the Fermi-contact shifts on two nuclei (6Li and 17O) to predict the optimal Ueff. The optimal Ueff is also helpful to the quadrupolar coupling constant CQ, g-factor, band structure and density of states.
The identification of reactive radical species using quenching and electron paramagnetic resonance (EPR) tests has attracted extensive attention, but some mistakes or misinterpretations are often ...present in recent literature. This review aims to clarify the corresponding issues through surveying literature, including the uncertainty about the identity of radicals in the bulk solution or adsorbed on the catalyst surface in quenching tests, selection of proper scavengers, data explanation for incomplete inhibition, the inconsistent results between quenching and EPR tests (e.g., SO4•− is predominant in quenching test while the signal of •OH predominates in EPR test), and the incorrect identification of EPR signals (e.g., SO4•− is identified by indiscernible or incorrect signals). In addition, this review outlines the transformation of radicals for better tracing the origin of radicals. It is anticipated that this review can help in avoiding mistakes while investigating catalytic oxidative mechanism with quenching and EPR tests.
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•The determination methods for detecting reactive radical species are summarized.•The uncertainty about the identity of radicals in quenching tests is proposed.•The misinterpretations over the radical identification in EPR tests are reviewed.•The transformation and interconversion of radicals are concluded.
Cancer causes the second-highest rate of death world-wide. A major shortcoming inherent in most of anticancer drugs is their lack of tumor selectivity. Nanodrugs for cancer therapy administered ...intravenously escape renal clearance, are unable to penetrate through tight endothelial junctions of normal blood vessels and remain at a high level in plasma. Over time, the concentration of nanodrugs builds up in tumors due to the EPR effect, reaching several times higher than that of plasma due to the lack of lymphatic drainage. This review will address in detail the progress and prospects of tumor-targeting via EPR effect for cancer therapy.
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