Spin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.
A covalent post-synthetic modification is applied in one of the most relevant polymers to obtain unprecedented switchable spin crossover (SCO) materials.
Detecting NO2 in an efficient manner is probably one of the major challenges to ensure a desired level of air quality. In spite of great efforts to surpass the current limitations, the commercial techniques are still strongly affected by interferences, are costly or difficult to implement in the field. Here, we investigate lanthanide metal-organic frameworks (Ln-MOF) for NO2 sensing with the aim of proposing a novel approach to surpass the present limitations. Precisely, two isostructural luminescent Ln-MOFs have been used including a recognition center (amino-group) that provides high selectivity for NO2 molecules. Energy transfer from the organic ligands to Ln is strongly dependent on the presence of NO2, resulting in an unprecedented photo-luminescent sensing scheme. Thereby, NO2 exposition triggers either a reversible enhancement or a decrease of the luminescence intensity, depending on the lanthanide (Eu or Tb). Our experimental studies combined with DFT and complete active space self-consistent field calculations, provide understanding of the nature and effects of NO2 interactions within the MOFs and the signal transduction mechanism.
We present here for the first time an exhaustive compilation of all systems in which the interaction between the coordination compounds and the vapour analytes leads to a colour change due to a spin transition in the metal centre at room temperature.
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