Tuning the carrier injection barrier of hybrid metal–organic interfaces on rare earth-gold surface compounds

Magnetic hybrid metal-organic interfaces possess a great potential in areas such as organic spintronics and quantum information processing. However, tuning their carrier injection barriers on-demand is fundamental for the implementation in technological devices. We have prepared hybrid metal-organic interfaces by the adsorption of copper phthalocyanine CuPc on REAu2 surfaces (RE = Gd, Ho and Yb) and studied their growth, electrostatics and electronic structure. CuPc exhibits a long-range commensurability and a vacuum level pinning of the molecular energy levels. We observe a significant effect of the RE valence of the substrate on the carrier injection barrier of the hybrid metal-organic interface. CuPc adsorbed on trivalent RE-based surfaces (HoAu2 and GdAu2) exhibits molecular level energies that may allow injection carriers significantly closer to an ambipolar injection behavior than in the divalent case (YbAu2)

A ferromagnetic Eu-Pt surface compound grown below hexagonal boron nitride

One of the fundamental applications for monolayer-thick 2D materials is their use as protective layers of metal surfaces and in situ intercalated reactive materials in ambient conditions. Here we investigate the structural, electronic, and magnetic properties, as well as the chemical stability in air of a very reactive metal, Europium, after intercalation between a hexagonal boron nitride (hBN) layer and a Pt substrate. We demonstrate that Eu intercalation leads to a hBN-covered ferromagnetic EuPt2 surface alloy with divalent Eu2+ atoms at the interface. We expose the system to ambient conditions and find a partial conservation of the di-valent signal and hence the Eu-Pt interface. The use of a curved Pt substrate allows us to explore the changes in the Eu valence state and the ambient pressure protection at different substrate planes. The interfacial EuPt2 surface alloy formation remains the same, but the resistance of the protecting hBN layer to ambient conditions is reduced, likely due to a rougher surface and a more discontinuous hBN coating

Influence of 4f filling on electronic and magnetic properties of rare earth-Au surface compounds

One-atom-thick rare-earth/noble metal (RE-NM) compounds are attractive materials to investigate two-dimensional magnetism, since they are easy to synthesize into a common RE-NM2 structure with high crystal perfection. Here we perform a comparative study of the GdAu2, HoAu2, and YbAu2 monolayer compounds grown on Au(111). We find the same atomic lattice quality and moiré superlattice periodicity in the three cases, but different electronic properties and magnetism. The YbAu2 monolayer reveals the characteristic electronic signatures of a mixed-valence configuration in the Yb atom. In contrast, GdAu2 and HoAu2 show the trivalent character of the rare-earth and ferromagnetic transitions below 22 K. Yet, the GdAu2 monolayer has an in-plane magnetic easy-axis, versus the out-of-plane one in HoAu2. The electronic bands of the two trivalent compounds are very similar, while the divalent YbAu2 monolayer exhibits different band features. In the latter, a strong 4f-5d hybridization is manifested in neatly resolved avoided crossings near the Fermi level. First principles theory points to a residual presence of empty 4f states, explaining the fluctuating valence of Yb in the YbAu2 monolayer. © The Royal Society of Chemistry

Correction: Influence of 4f filling on electronic and magnetic properties of rare earth-Au surface compounds

Correction for 'Influence of 4f filling on electronic and magnetic properties of rare earth-Au surface compounds' by L. Fernandez et al., Nanoscale, 2020, 12, 22258–22267, DOI: 10.1039/D0NR04964F

Conjugates of Cryptophycin and RGD or isoDGR Peptidomimetics for Targeted Drug Delivery

RGD\u2010cryptophycin and isoDGR\u2010cryptophycin conjugates were synthetized by combining peptidomimetic integrin ligands and cryptophycin, a highly potent tubulin\u2010binding antimitotic agent across lysosomally cleavable Val\u2010Ala or uncleavable linkers. The conjugates were able to effectively inhibit binding of biotinylated vitronectin to integrin \u3b1v\u3b23, showing a binding affinity in the same range as that of the free ligands. The antiproliferative activity of the novel conjugates was evaluated on human melanoma cells M21 and M21\u2010L with different expression levels of integrin \u3b1v\u3b23, showing nanomolar potency of all four compounds against both cell lines. Conjugates containing uncleavable linker show reduced activity compared to the corresponding cleavable conjugates, indicating efficient intracellular drug release in the case of cryptophycin\u2010based SMDCs. However, no significant correlation between the in\u2005vitro biological activity of the conjugates and the integrin \u3b1v\u3b23 expression level was observed, which is presumably due to a non\u2010integrin\u2010mediated uptake. This reveals the complexity of effective and selective \u3b1v\u3b23 integrin\u2010mediated drug delivery

Daily activity patterns in captive elephant shrews (Macroscelididae)

The activity patterns of six species of captive elephant shrews {Elephantulus (four species), Macroscelides and Petrodromus) were monitored electronically for periods of 48 h. Individual animals showed some significant differences in activity from one day to the next but generally followed the same pattern of diel activity. Intraspecific differences were observed in eight Elephantulus edwardii and seven Elephantulus myurus but all had a similar overall pattern of activity apart from a possibly diseased E. edwardii and two E. myurus, which had previously been exposed to a high level of human disturbance, and which showed increased nocturnal activity. All species were active, to varying degrees, both day and night. Interspecific differences in activity exhibited a continuum, with different species showing differing periods of peak activity. Differences in the nocturnal/diurnal ratio may be related to the amount of cover in the habitat and the degree of aridity experienced by each species. Significant seasonal differences in activity were noted in two species where sample sizes were adequate to permit their detection. On a surveilléélectroniquement le schéma d'activité de six espéces de rats à trompe en captivité par tranche de 48 h. Individuellement, les animaux présentent quelques différences significatives d'un jour à l'autre mais suivent généralement le même schéma d'activité. Des différences intraspécifiques furent observées chez huit Elephantulus edwardii et sept E. myurus mais tous avaient un schéma d'activités globalement similaire, aF l'exception d'un E. edwardii, peut‐être malade, et de deux E. myurus qui avaient ete auparavant soumis à de grands dérangements, et qui montraient un accroissement de l'activité nocturne. Toutes les espèces étaient actives, à des degrés divers, jour et nuit. Les différences interspécifiques étaient permanentes, les espèces présentant des périodes d'activité maximales diffeareés. Les différences du rapport diurne/nocturne peuvent être mises en relation avec le degré de couvertre de l'habitat et le degré d'aridité aux quels est soumise chaque espèce. On a noté des différences d'activité saisonnières significatives chez deux espèces dont la taille de l'echantillon permettait de les détecter

Seasonal variation in the estrous cycle of mares in the subtropics

Data on the estrous cycles and sexual receptivity scores of 7 maiden Australian Stock Horse mares were used to study seasonal variation from December until the following November. Mares were grazed in paddocks containing both native and improved tropical pasture species. The study was conducted in South-East Queensland (27°27′ South latitude). There were no differences between either the sexual receptivity or the lengths of natural (Mean=7.5 days, SEM=0.4) and PGF-induced estruses (Mean=7.6 days, SEM=0.4). Plasma estrogens were not related to differences in sexual receptivity scores between mares. The lowest incidence of estrus occurred at the time of the winter solstice (June 22) in the Southern Hemisphere. Winter estruses (Mean=9.3 days, SEM=0.8) were longer than those of summer (Mean=6.6 days, SEM=0.5) and autumn (Mean=6.6 days, SEM=0.9). Approximately 30% of estruses were anovulatory. Most of these occurred in autumn and winter (