The degree of $B/B^{\prime }$ alternate cation order is known to heavily influence the magnetic properties of $A_{2}B{B}^{\prime }{\mathrm{O}}_6$ double perovskites although the nature of such disorder has never been critically studied. Our detailed x-ray absorption fine structure studies in conjunction with synchrotron radiation x-ray diffraction experiments on polycrystalline ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ samples with various degrees of disorder reveal that a very high degree of short range order is preserved even in samples with highly reduced long range chemical order. Based on these experimental results and with the help of detailed structural simulations, we are able to model the nature of the disorder in this important class of materials and discuss the consequent implications on its physical properties.

Nanostructured materials characterized by high surface–volume ratio hold the promise to constitute the active materials for next‐generation sensors. Solution‐processed hybrid organohalide perovskites, which have been extensively used in the last few years for optoelectronic applications, are characterized by a self‐assembled nanostructured morphology, which makes them an ideal candidate for gas sensing. Hitherto, detailed studies of the dependence of their electrical characteristics on the environmental atmosphere have not been performed, and even the effect of a ubiquitous gas such as O₂ has been widely overlooked. Here, the electrical response of organohalide perovskites to oxygen is studied. Surprisingly, a colossal increase (3000‐fold) in the resistance of perovskite‐based lateral devices is found when measured in a full oxygen atmosphere, which is ascribed to a trap healing mechanism originating from an O₂‐mediated iodine vacancies filling. A variation as small as 70 ppm in the oxygen concentration can be detected. The effect is fast (<400 ms) and fully reversible, making organohalide perovskites ideal active materials for oxygen sensing. The effect of oxygen on the electrical characteristics of organohalide perovskites must be taken into deep consideration for the design and optimization of any other perovskite‐based (opto‐) electronic device working in ambient conditions.

The isolation of 2D-materials is already a success for graphene, graphene oxide, boron nitride and a few clays or metal chalcogenides, however despite the fact that some of them show very interesting physical properties, they lack useful functionalities. Metal–Organic Frameworks (MOFs) are multifunctional materials showing a wide range of physical and chemical properties that can be structurally designed by suitable selection of their building-blocks. This strategy may allow the production of layers with a variety of useful electronic and molecular recognition functionalities. Herein we isolate 2D-MOF flakes with areas of hundreds of square microns and an excellent control of the molecular thickness (from single up to ca. 50 layers). The samples exhibit such good photoluminescence and mechanical properties as to allow free-standing characterization of few layers’ flakes.

We exploited the solvatochromic spin-state switching in a spin crossover (SCO) compound based on the Fe^II complex and the simultaneous change of spectroscopic properties for selective multimodal sensing of methanol and ethanol. We demonstrate that sensing capabilities are due to the inclusion of methanol or ethanol molecules into the crystalline structure, which tailors simultaneously the transition temperature, colour, birefringence and vibrational modes. We exploited this capability by integrating a neutral compound, switchable at room temperature, into a micrometric TAG sensitive to the colour and birefringence. The system was characterised by optical microscopy, magnetic susceptibility, Raman spectroscopy and X-ray diffraction.