Cooperative effects determine the spin-state bistability of spin-crossover molecules (SCMs). Herein, the ultimate scale limit at which cooperative spin switching becomes effective is investigated in a complex [Fe(H2B(pz)2)2(bipy)] deposited on a highly oriented pyrolytic graphite surface, using x-ray absorption spectroscopy. This system exhibits a complete thermal- and light-induced spin transition at thicknesses ranging from submonolayers to multilayers. On increasing the coverage from 0.35(4) to 10(1) monolayers, the width of the temperature-induced spin transition curve narrows significantly, evidencing the buildup of cooperative effects. While the molecules at the submonolayers exhibit an apparent anticooperative behavior, the multilayers starting from a double-layer exhibit a distinctly cooperative spin switching, with a free-molecule-like behavior indicated at around a monolayer. These observations will serve as useful guidelines in designing SCM-based devices.

The spontaneous ordering of molecules into two-dimensional self-assembled arrays is commonly stabilized by directional intermolecular interactions that may be promoted by the addition of specific chemical side groups to a molecule. In this paper, we show that self-assembly may also be driven by anisotropic interactions that arise from the three-dimensional shape of a complex molecule. We study the molecule mn 12 o 12 (o 2 CCH 3 ) 16 (H 2 o) 4 (mn 12 (acetate) 16 ), which is transferred from solution onto a Au(111) substrate held in ultrahigh vacuum using electrospray deposition (uHV-EsD). The deposited mn 12 (acetate) 16 molecules form filamentary aggregates because of the anisotropic nature of the molecule-molecule and molecule-substrate interactions, as confirmed by molecular dynamics calculations. The fragile mn 12 o 12 core of the mn 12 (acetate) 16 molecule is compatible with the uHV-EsD process, which we demonstrate using near-edge X-ray adsorption fine-structure spectroscopy. uHV-EsD of mn 12 (acetate) 16 onto a surface that has been prepatterned with a hydrogen-bonded supramolecular network provides additional control of lateral organization.

For probing the nature of spin-state switching in spin-crossover molecules adsorbed on surfaces, x-ray absorption spectroscopy has emerged as a powerful tool due to its high sensitivity and element selectivity in tracing even subtle electronic, magnetic, or chemical changes. However, the x-rays itself can induce a spin transition and might have unwanted influence while investigating the effect of other stimuli such as temperature or light, or of the surface, on the spin switching behaviour. Herein, we present the spin switching of an Fe(II) complex adsorbed on a highly oriented pyrolytic graphite surface with particular emphasis on the x-ray-induced switching. For a submonolayer coverage, the complex undergoes a complete and reversible temperature- and light-induced spin transition. The spin states are switched both ways by x-rays at 5 K, i.e. from the high-spin state to the low-spin state or vice versa, depending on the relative amount of each species. Furthermore, we quantify the fraction of molecules undergoing soft x-ray-induced photochemistry, a process which results in an irreversible low-spin state component, for a particular exposure time. This can be greatly suppressed by reducing the beam intensity.

I-V-VI2 ternary chalcogenides are gaining attention as earth-abundant, nontoxic, and air-stable absorbers for photovoltaic applications. However, the semiconductors explored thus far have slowly-rising absorption onsets, and their charge-carrier transport is not well understood yet. Herein, we investigate cation-disordered NaBiS2 nanocrystals, which have a steep absorption onset, with absorption coefficients reaching >105 cm−1 just above its pseudo-direct bandgap of 1.4 eV. Surprisingly, we also observe an ultrafast (picosecond-time scale) photoconductivity decay and long-lived charge-carrier population persisting for over one microsecond in NaBiS2 nanocrystals. These unusual features arise because of the localised, non-bonding S p character of the upper valence band, which leads to a high density of electronic states at the band edges, ultrafast localisation of spatially-separated electrons and holes, as well as the slow decay of trapped holes. This work reveals the critical role of cation disorder in these systems on both absorption characteristics and charge-carrier kinetics.

Gastroblastoma is a newly defined neoplasm of children and young adults with only 4 reported cases to date. Morphologically, the tumor is a mixture of epithelial structures and stromal elements with minimal cytologic atypia. In these 4 reported cases, there were no metastases or postresection recurrences. We report a case of gastroblastoma in a 28-year-old man with a histologic nodal metastasis and clinical distant metastases.