Fast, broad-band magnetic resonance spectroscopy with diamond widefield relaxometry

We present an alternative to conventional Electron Paramagnetic Resonance spectroscopy equipment. Avoiding the use of bulky magnets and magnetron equipment, we use the photoluminescence of an ensemble of Nitrogen-Vacancy centers at the surface of a diamond. Monitoring their relaxation time (or T1), we detected their cross-relaxation with the compound of interest. In addition, the EPR spectra is encoded through a localized magnetic field gradient. While 12 minutes was necessary to record each data point of the spectrum with previous individual NV center's technics, we are able to reconstruct a full spectrum at once in 3 seconds, over a range from 3 to 11 gauss. In term of sensitivity, only 0.5 microliter of a hexaaquacopper (II) ion solution with 1 micromole per liter concentration was necessary.Comment: Main text (15 pages, 6 Figures) + Supplementary (6 Pages, 7 Figures

Diamond Color Centers in Diamonds for Chemical and Biochemical Analysis and Visualization

Beyond the sparkle, other properties of diamond havegained increasing attention in the past few decades amongchemists and physicists. Color centers-impurities formed byone or a few foreign atoms or vacancies in the diamondlattice-are one reason for this. While pure diamond istransparent, the presence of color centers causes changes incoloration. Color centers introduce additional electronic statesin the wide band gap of diamond, giving rise to transitions thatabsorb and emit light in the visible spectrum

Binder evaporation during powder sheet Additive Manufacturing

Several Additive Manufacturing methods are well established and found access into regular production in multiple sectors. For processing metals, typically wire or powder is used as feedstock. Wire processing is typically used for comparably large structure building, while powder processes offer, in general, a more precise metal application. For Powder Bed Fusion processes, very fine powder is used (typical 20 µm to 65 µm), while for Directed Energy Deposition powders are in the range between 50 µm and 160 µm. Such fine powders can be a health risk for humans (aspiration, skin integration). Avoiding contact with the powders in a production environment can be a big effort or not avoidable. Therefore, an alternative process was developed that provides the powder not as free powder particles but in form of powder sheets. For enabling the necessary bonding between the particles, a binder is used. In order to understand the impact of the binder during laser processing of the powder sheets, single pulse and line treatments were produced and recorded with high-speed imaging. Recordings show the vaporization of the binder and the related ejections of powder particles. At lower energy input, the binder evaporation led to less spattering, which indicates that a binder heating at low heating rates induces less pressure on the powder particles.Mechanical Engineerin

High Temperature Treatment of Diamond Particles Toward Enhancement of Their Quantum Properties

Fluorescence of the negatively charged nitrogen-vacancy (NV-) center of diamond is sensitive to external electromagnetic fields, lattice strain, and temperature due to the unique triplet configuration of its spin states. Their use in particulate diamond allows for the possibility of localized sensing and magnetic-contrast-based differential imaging in complex environments with high fluorescent background. However, current methods of NV(-)production in diamond particles are accompanied by the formation of a large number of parasitic defects and lattice distortions resulting in deterioration of the NV(-)performance. Therefore, there are significant efforts to improve the quantum properties of diamond particles to advance the field. Recently it was shown that rapid thermal annealing (RTA) at temperatures much exceeding the standard temperatures used for NV(-)production can efficiently eliminate parasitic paramagnetic impurities and, as a result, by an order of magnitude improve the degree of hyperpolarization of(13)C via polarization transfer from optically polarized NV(-)centers in micron-sized particles. Here, we demonstrate that RTA also improves the maximum achievable magnetic modulation of NV(-)fluorescence in micron-sized diamond by about 4x over conventionally produced diamond particles endowed with NV-. This advancement can continue to bridge the pathway toward developing nano-sized diamond with improved qualities for quantum sensing and imaging

Transient Formation and Reactivity of a High-Valent Nickel(IV) Oxido Complex

A reactive high-valent dinuclear nickel(IV) oxido bridged complex is reported that can be formed at room temperature by reaction of [(L)2Ni(II)2(μ-X)3]X (X = Cl or Br) with NaOCl in methanol or acetonitrile (where L = 1,4,7-trimethyl-1,4,7-triazacyclononane). The unusual Ni(IV) oxido species is stabilized within a dinuclear tris-μ-oxido-bridged structure as [(L)2Ni(IV)2(μ-O)3]2+. Its structure and its reactivity with organic substrates are demonstrated through a combination of UV-vis absorption, resonance Raman, 1H NMR, EPR, and X-ray absorption (near-edge) spectroscopy, ESI mass spectrometry, and DFT methods. The identification of a Ni(IV)-O species opens opportunities to control the reactivity of NaOCl for selective oxidations

H2O2 Oxidation by Fe-III-OOH Intermediates and Its Effect on Catalytic Efficiency

The oxidation of the C-H and C=C bonds of hydrocarbons with H2O2 catalyzed by non-heme iron complexes with pentadentate ligands is widely accepted as involving a reactive Fe-IV=O species such as [(N4Py)Fe-IV=O](2+) formed by homolytic cleavage of the O-O bond of an Fe-III-OOH intermediate (where N4Py is 1,1-bis(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine). We show here that at low H2O2 concentrations the Fe-IV=O species formed is detectable in methanol. Furthermore, we show that the decomposition of H2O2 to water and O-2 is an important competing pathway that limits efficiency in the terminal oxidant and indeed dominates reactivity except where only sub-/near-stoichiometric amounts of H2O2 are present. Although independently prepared [(N4Py)Fe-IV=O](2+) oxidizes stoichiometric H2O2 rapidly, the rate of formation of Fe-IV=O from the Fe-III-OOH intermediate is too low to account for the rate of H2O2 decomposition observed under catalytic conditions. Indeed, with excess H2O2, disproportionation to O-2 and H2O is due to reaction with the Fe-III-OOH intermediate and thereby prevents formation of the Fe-IV=O species. These data rationalize that the activity of these catalysts with respect to hydrocarbon/alkene oxidation is maximized by maintaining sub-/near-stoichiometric steady-state concentrations of H2O2, which ensure that the rate of the H2O2 oxidation by the Fe-III-OOH intermediate is less than the rate of the O-O bond homolysis and the subsequent reaction of the Fe-IV=O species with a substrate

Plasma assisted bio-degradation of poly-lactic acid (PLA)

Plastics are artificial synthetic organic polymers that have been used in every area of daily life. However, because of their slow degradation rate, their use is contentious. The treatment of the surface of the sample is considered necessary as enzymatic or bacterial attach is not possible, if the plastic surface environment is not ideal. The main topic of this work is the investigation of the effect of atmospheric dielectric barrier discharge (DBD) plasma on the near surface structure of polylactic acid (PLA) samples, which, in turn, can promote the adhesion of enzymes or bacteria for further biodegradation. In general, plasma processes can already be considered as inherently environmental technologies. Plasma processes enable resource saving through high energy utilization efficiency and thus, are environ-mentally friendly technologies. Atmospheric pressure discharges (APDs) are useful because of their specific advantages over low-pressure ones. They do not need expensive vacuum equipment, and generate nonthermal plasmas, which are more suitable for assembly line processes. Hence, this category of discharges has significant industrial applications. The use of a dielectric barrier in the discharge gap helps prevent spark formation. DBDs exhibit two major discharge modes: filamentary and glow (homogeneous). The glow discharge mode has obvious advantages over the filamentary one for applications such as treatment of surfaces and deposition of thin films. Glow mode discharges with average power densities comparable to those of filamentary discharges are of enormous interest for applications in which reliable control is required. Here we will present the increased adhesion of bacteria strains on DBD plasma treated PLA foils which can lead to a better degradation of the PLA. X-ray photoelectron spectroscopy (XPS) measurements of the foils prior to and after the treatment proved the changes on the polymer surface. A short discussion of the possibilities the treatment opens is given.CHANIA 2023: 10th International Conference on Sustainable Solid Waste Management Chania, Greece, 21 - 24 JUNE 202

Conflicting Role of Water in the Activation of H2O2 and the Formation and Reactivity of Non-Heme Fe-III-OOH and Fe-III-O-Fe-III Complexes at Room Temperature

The formation of an Fe-III-OOH species by reaction of complex 1 ([(MeN3Py)Fe-II(CH3CN)(2)](2+)) with H2O2 at room temperature is reported and is studied by a combination of UV/vis absorption, EPR, and resonance Raman spectroscopies. The formation of the Fe-III-OOH species, and its subsequent conversion to relatively inert Fe-III-O-Fe-III species, is shown to be highly dependent on the concentration of water, with excess water favoring the formation of the latter species, which is studied by UV/vis absorption spectroelectrochemistry also. The presence of acetic acid increases the rate and extent of oxidation of 1 to its iron(III) state and inhibits the wasteful decomposition of H2O2 but does not affect significantly the spectroscopic properties of the Fe-III-OOH species formed

O2 Activation and Double CH Oxidation by a Mononuclear Manganese(II) Complex

A Mn(II) complex, [Mn(dpeo)2 ](2+) (dpeo=1,2-di(pyridin-2-yl)ethanone oxime), activates O2 , with ensuing stepwise oxidation of the methylene group in the ligands providing an alkoxide and ultimately a ketone group. X-ray crystal-structure analysis of an intermediate homoleptic alkoxide Mn(III) complex shows tridentate binding of the ligand via the two pyridyl groups and the newly installed alkoxide moiety, with the oxime group no longer coordinated. The structure of a Mn(II) complex of the final ketone ligand, cis-[MnBr2 (hidpe)2 ] (hidpe=2-(hydroxyimino)-1,2-di(pyridine-2-yl)ethanone) shows that bidentate oxime/pyridine coordination has been resumed. H2 (18) O and (18) O2 labeling experiments suggest that the inserted O atoms originate from two different O2 molecules. The progress of the oxygenation was monitored through changes in the resonance-enhanced Raman bands of the oxime unit