Single-nanoparticle phase transitions visualized by four-dimensional electron microscopy

The advancement of techniques that can probe the behaviour of individual nanoscopic objects is of paramount importance in various disciplines, including photonics and electronics. As it provides images with a spatiotemporal resolution, four-dimensional electron microscopy, in principle, should enable the visualization of single-nanoparticle structural dynamics in real and reciprocal space. Here, we demonstrate the selectivity and sensitivity of the technique by visualizing the spin crossover dynamics of single, isolated metal–organic framework nanocrystals. By introducing a small aperture in the microscope, it was possible to follow the phase transition and the associated structural dynamics within a single particle. Its behaviour was observed to be distinct from that imaged by averaging over ensembles of heterogeneous nanoparticles. The approach reported here has potential applications in other nanosystems and those that undergo (bio)chemical transformations

Experimental and theoretical studies of the reaction of atomic hydrogen with silane

Article on experimental and theoretical studies of the reaction of atomic hydrogen with silane

Temperature- and Light-Induced Spin Crossover Observed by X-ray Spectroscopy on Isolated Fe(II) Complexes on Gold

Using X-ray absorption techniques, we show that temperature- and light-induced spin crossover properties are conserved for a submonolayer of the [Fe(H2B(pz)2)2(2,2′-bipy)] complex evaporated onto a Au(111) surface. For a significant fraction of the molecules, we see changes in the absorption at the L2,3 edges that are consistent with those observed in bulk and thick film references. Assignment of these changes to spin crossover is further supported by multiplet calculations to simulate the X-ray absorption spectra. As others have observed in experiments on monolayer coverages, we find that many molecules in our submonolayer system remain pinned in one of the two spin states. Our results clearly demonstrate that temperature- and light-induced spin crossover is possible for isolated molecules on surfaces but that interactions with the surface may play a key role in determining when this can occur

Nanohybrids with magnetic and persistent luminescence properties for cell labelling, tracking, in vivo real-time imaging and magnetic vectorization

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Soft Lithographic Patterning of Spin Crossover Nanoparticles

International audienceMicrotransfer molding has been used to fabricate homogeneous micropatterns and nanopatterns of spin crossover nanoparticles of [Fe(NH2trz)](tos)2 over a large area. We show that the use of an aprotic solvent (n-octane) may lead to successful results. Very well organized micropatterns are obtained, showing spin crossover phenomenon. Dark field optical and AFM images and Raman microspectrometry results are reported

Size effect in spin-crossover systems investigated by FORC measurements, for surfacted [Fe(NH 2-trz) 3](Br) 2·3H 2O nanoparticles: reversible contributions and critical size

International audienceWe investigated the thermal transition of coated nano-particles of the title compound, on a set of samples of average diameter ⟨d⟩ ~ 30, 50, 70, 110 nm, with rather broad size distributions. As expected, the width of the major hysteresis loop was an increasing function of ⟨d⟩. We recorded first-order reversal curves (FORC), the initial parts of which displayed a finite slope, revealing the presence of reversible contributions expected from particles smaller than the critical size dC associated with the collapse of the hysteresis loop. Kinetic effects were also evidenced thanks to isothermal stages. Reversibility of the FORC curves at the vicinity of the reversal temperature was controlled. Thanks to the reversibility property we could determine the reversible contributions to the total response of all samples and derive the corresponding dC values. Consistent results were obtained by accounting for an anhysteretic contribution from the large particles, leading to an accurate determination dC ~ 45−50 nm, much better than the width of the size distributions