The Impact of Lattice Distortions on the Magnetic Stability of Single Atoms: Dy and Ho on BaO(100)

X-ray magnetic circular dichroism, atomic multiplet simulations, and density functional theory calculations are employed to identify criteria for the optimum combination of supporting alkaline earth oxide and adsorption site maximizing the spin lifetimes of lanthanide single-atom magnets. Dy and Ho atoms adsorbed on BaO(100) thin films on Pt(100) are characterized and compared with previous results for the same two elements on MgO/Ag(100). Dy shows hysteresis in magnetic fields up to ≈3.5 T and long spin lifetime, exceeding 300 s at 2.5 K and 0.5 T. Dy displays superior magnetic stability on the bridge site than on the top-O site. Surprisingly, Ho shows paramagnetism, as opposed to its long spin lifetime on MgO. These differences originate from the local surface distortions induced by the adatoms. On MgO, minimal distortions involve only the closest O atoms, while, on BaO, they affect both the closest anions and cations. This trend reflects the decrease of the lattice energy along the series of the alkaline earth oxides, going from MgO to BaO. This study represents a step ahead in the understanding of the factors determining the spin dynamics of surface-adsorbed single-atom magnets in order to achieve their operation as qubits and memories.     

Front Cover: Chemoselective Labeling and Immobilization of Phosphopeptides with Phosphorimidazolide Reagents (ChemBioChem 4/2023)

Protein phosphorylation is one of the most ubiquitous post-translational modifications, regulating numerous essential processes in cells. Accordingly, the large-scale annotation of phosphorylation sites continues to provide central insight into the regulation of signaling networks. The global analysis of the phosphoproteome typically relies on mass spectrometry analysis of phosphopeptides, with an enrichment step necessary due to the sub-stoichiometric nature of phosphorylation. Several affinity-based methods and chemical modification strategies have been developed to date, but the choice of enrichment method can have a considerable impact on the results. Here, we show that a biotinylated, photo-cleavable phosphorimidazolide reagent permits the immobilization and subsequent cleavage of phosphopeptides. The method is capable of the capture and release of phosphopeptides of varying characteristics, and this mild and selective strategy expands the current repertoire for phosphopeptide chemical modification with the potential to enrich and identify new phosphorylation sites in the future.     

Giant Pressure-Induced Spectral Shift in Cyan-Emitting Eu2+-Activated Sr8Si4O12Cl8 Microspheres for Ultrasensitive Visual Manometry

To address the unsatisfactory pressure sensitivity of luminescent manometers, Eu²⁺-activated supersensitive microspheres operating in the visible range are developed. A series of Eu²⁺-doped Sr₈Si₄O₁₂C_l8 materials are synthesized as microspheres, and their structural and spectroscopic properties are studied theoretically and experimentally. Excited at 350 nm, the samples emit a bright cyan luminescence at ambient conditions that, upon pressure, changes to green emission and finally to yellow light above 7 GPa. Most importantly, a huge red-shift of the emission band from 497.3 to 568.8 nm is observed as the pressure increases, leading to an ultrahigh-pressure sensitivity of 9.69 nm/GPa, which is the highest sensitivity ever reported. The designed microspheres with polychromatic emissions and high-pressure sensitivity are suitable for visual optical pressure sensing, and the applied strategy provides some important guidelines for the development of new optical manometers, allowing pressure monitoring with unprecedented accuracy.     

A Universal Synthesis Strategy for Lanthanide Sulfide Nanocrystals with Efficient Photocatalytic Hydrogen Production

As an important lanthanide (Ln)-based functional materials, the Ln chalcogenides possess unique properties and various applications. However, the controllable synthesis of Ln chalcogenide nanocrystals still faces great challenges because of the rather poor affinity between Ln and chalcogenide ions (S, Se, Te) as well as strong preference of combination with existed oxygen. Herein, a facile but general heterogeneous nucleation synthetic strategy is established toward a series of colloidal ternary Cu Ln sulfides nanocrystals using the Ln dithiocarbamates and CuI as precursors. To extend this synthetic protocol, similar strategy is used to prepare six kinds of high quality CuLnS₂ nanocrystals, while the bulk ones are only obtained by the traditional solid-state reaction at rigorous condition. Importantly, high-entropy nanocrystals CuLnS₂ and CuEu_xLn_2-xS₃ which contain six Ln elements (Nd, Sm, Gd, Tb, Dy) are readily obtained by the co-decomposed process attributed to their similar diffusion speed. As a proof-of-concept application, CuEu₂S₃ nanocrystals showed efficient photocatalytic hydrogen production properties.