Spins in molecules are particularly attractive targets for next-generation quantum technologies, enabling chemically programmable qubits and potential for scale-up via self-assembly. Here we report ...the observation of one of the largest hyperfine interactions for a molecular system, A
= 3,467 ± 50 MHz, as well as a very large associated clock transition. This is achieved through chemical control of the degree of s-orbital mixing into the spin-bearing d orbital associated with a series of spin-½ La(II) and Lu(II) complexes. Increased s-orbital character reduces spin-orbit coupling and enhances the electron-nuclear Fermi contact interaction. Both outcomes are advantageous for quantum applications. The former reduces spin-lattice relaxation, and the latter maximizes the hyperfine interaction, which, in turn, generates a 9-GHz clock transition, leading to an increase in phase memory time from 1.0 ± 0.4 to 12 ± 1 μs for one of the Lu(II) complexes. These findings suggest strategies for the development of molecular quantum technologies, akin to trapped ion systems.
Essential oils (EOs) extracted from aromatic plants have been well recognized for their insect repellent properties. Although EOs are effective when freshly applied, their protective effect usually ...dissipates quickly due to low chemical stability and rapid volatilization of their ingredients. To address this issue, encapsulation in protective carrier materials at the nanoscale is proposed. In this study, oil-in-water (O/W) microemulsions containing geraniol or Citrepel® 75 (citrepel) as the oil phase, a mixture of water and diethylene glycol monoethyl ether (DEGEE) as the aqueous phase and caprylocaproyl polyoxyl-8 glycerides as surfactant were formulated and structurally characterized. DLS analysis showed that the emulsified oil droplets had low polydispersity (PdI<0.3) and average hydrodynamic diameter ranging from 13.7 ± 0.7–35.2 ± 2.7 nm, depending on composition. Mean viscosity of all prepared microemulsions was from 15.7 ± 0.3 cP to 23.8 ± 0.2 cP indicating the suitability of all preparations for topical application. EPR spectroscopy using spin probes gave information about the rigidity of the surfactants’ monolayer. In all cases an outer compact configuration of the interfacial layer and a more flexible inner one was observed. SAXS measurements revealed significant changes in the low q values related to the impact of geraniol and citrepel in microemulsion formulations. Looking at the high q region of the spectra, the curves were affected by the presence of the compounds in a concentration depended manner. Cytotoxicity studies on normal human epidermal keratinocytes (NHKs) confirmed that the sub-toxic dosage for geraniol-in-water and citrepel-in-water microemulsions is 56.25 μg active ingredient per cm2 of cell monolayer. Finally, diluted geraniol-in-water microemulsions were evaluated for repellence action against the Asian tiger mosquito (Aedes albopictus) showing activity for 3 h at a dose of 190 μg/cm2 active ingredient. Gaining a comprehensive understanding from all the results, promising candidates for topical application of geraniol as insect repellent based on safe microemulsions were proposed.
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•O/W microemulsions (MEs) containing geraniol and citrepel were obtained.•The effect of composition on physical properties was studied with DLS, SAXS, EPR.•Cytotoxicity studies indicated the sub-toxic dose of geraniol and citrepel in MEs.•Diluted geraniol-in-water microemulsions were active against Asian tiger mosquito.
The black we wear: Why nature selected 5,6‐dihydroxyindole‐2‐carboxylic acid (DHICA) to synthesize (photo)protective eumelanin pigments is an enigma. Synthetic DHICA eumelanin has now been shown to ...be a highly efficient free‐radical scavenger in the solid state, which is due to a conformationally interrupted π‐electron network associated with atypical optical, paramagnetic, and aggregation properties.
Na+2Eu3+2:Ca6(PO4)6F2 is explored as a potential host for radioactive waste immobilization. Since Eu3+ ion is a surrogate of highly radioactive Am3+ ion, the photoluminescence (PL) characteristics of ...Eu3+ ion helped to investigate the possible distribution of hazardous and radioactive Am3+ ion among the two lattice sites in the matrix. It was observed that Am3+ will prefer to occupy the Ca2-site lattice which has a direct linkage to F atom. From DFT calculation we have found that both Eu3+ and Am3+ ions are following similar trend of distribution into the Ca2-site compared to Ca1-site which has no F atom linkage. The radiation stability of the compound was also investigated by PL study after irradiating it with a 60Co gamma source with different doses starting from 2 kGy to as high as 1000 kGy. It was observed that radiation induced changes were more surrounding the Ca1-site than in Ca2-site.Considering all the experimental and theoretical observations it is concluded that from radioactive waste immobilization point of view it is more preferable to dope the Am3+ ion into the Ca2 site. The Eu3+ doped compound was also found to be red color emitting phosphor materials with color purity of 95.24%.
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•Ca10(PO4)6F2 was explored as a host for radioactive waste immobilization.•Distribution of highly radioactive and hazardous 241Am3+ ions was investigated.•Eu3+ ion was used as a surrogate of Am3+ ion.•Radiation stability of the compound was investigated.•Ca2 site offers more radiation stability to Am3+ ion.
Despite the notable progress in the stabilization of main group radicals by NHCs and cAACs, no germanium radicals have been isolated so far due to synthetic challenges. Stabilization of neutral :EIR• ...(E = Si, Ge) radicals is an uphill task, as these reactive transient species are highly susceptible to dimerization. Herein, we report the synthesis of acyclic neutral germanium(I) radicals Cy-cAAC:GeN(SiMe3)Dip (1) and Me-cAAC:GeN(SiPh3)Mes (2) obtained by the reduction of Ar(SiR3)NGeCl3 with KC8 in the presence of cAAC. Compounds 1 and 2 are well characterized by single crystal X-ray structural analysis, cyclic voltammetry, and EPR spectroscopy. Furthermore, the structure and bonding of compounds 1 and 2 have been investigated by theoretical methods.
The synthesis of the new nitroxide crown ether 8 and its use as the wheel in a bistable 2rotaxane, containing dialkylammonium and 4,4′‐bipyridinium recognition sites, is reported. The synthesis of 8 ...was achieved by the sequential addition of substituted phenyl groups to a nitrone derivatives leading to the preferential formation of the cis stereoisomer. Due to charge–dipole interactions between the nitroxide unit and the bipyridinium moiety, it was possible to probe the movement of the macrocycle between the two molecular stations of the 2rotaxane after addition of a base by measuring the nitrogen hyperfine splitting in the corresponding EPR spectra. The equilibrium constant for the complexation of dibenzyl viologen by the macrocycle 8 was also determined by EPR titration.
Moving wheel: The synthesis of a nitroxide crown ether and its use as the wheel in a bistable 2rotaxane is reported (see figure). It is shown that the EPR read‐out discriminates between dialkylammonium and 4,4′‐bipyridinium recognition sites and this favourable feature can be used to probe the shuttling process of the paramagnetic wheel.
•Two ZnFe2O4 samples were prepared by co-precipitation and template syntheses.•A combination of spectroscopic techniques was used to verify the sample purity.•In situ synchrotron X-ray diffraction ...patterns were interpreted on the base of physico-chemical features.
ZnFe2O4 (ZFO) has emerged as anode material for lithium ion batteries (LIBs) thanks to its intercalation mechanism combining conversion and alloying reactions. The understanding of electrochemical behaviour is related to the knowledge of the physico-chemical properties of electrode materials. In this paper, ZFO was prepared by co-precipitation and template syntheses, obtaining samples with different morphologies and crystallite sizes. The sample purity was verified by combining X-ray powder diffraction with spectroscopic techniques such as Micro-Raman, EPR and Mössbauer. The electrochemical features, measured by using conventional cyclic voltammetry, impedance spectroscopy, charge-discharge measurements and in situ X-ray diffraction experiments, were then interpreted on the basis of the physico-chemical features. The higher electrode area of the template ZFO, with smaller particles, is responsible for better reactivity in the first cycles, but, in the long term, a lower crystallinity of active material, leading to nano-crystalline reaction products, could determine a better reversibility.
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Structural and dynamical characterization of proteins is of central importance in understanding the mechanisms underlying their biological functions. Site-directed spin labeling (SDSL) combined with ...continuous-wave electron paramagnetic resonance (CW EPR) spectroscopy has shown the capability of providing this information with site-specific resolution under physiological conditions for proteins of any degree of complexity, including those associated with membranes. This chapter introduces methods commonly employed for SDSL and describes selected CW EPR-based methods that can be applied to (1) map secondary and tertiary protein structure, (2) determine membrane protein topology, (3) measure protein backbone flexibility, and (4) reveal the existence of conformational exchange at equilibrium.
A series of CaYAl3O7 phosphors doped with different concentrations of Pb2+ were prepared by an auto solution combustion route. The structure, luminescence, and electron paramagnetic resonance (EPR) ...spectra were analysed. The X-ray diffraction (XRD) patterns identify the tetragonal phase formation of CaYAl3O7 with a crystallite size in a range of 37–42 nm. The scanning electron microscope (SEM) images were captured to study the surface morphology of the prepared samples. The emission spectra for the prepared phosphors exhibit a wide emission band centered at 362 nm under 270 nm excitation. Un-doped and Pb2+ doped CaYAl3O7 phosphor exhibit an EPR spectrum which arises from two noticeable defect centers. Center I with a g-value equal to 1.96 and a relatively broad line width is temporarily defined to an F+ - center (an electron trapped at an anion vacancy). Center II with g = 2.0 is also ascribed to an F+ - center.
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