Antonio Cassinese

2D structures have numerous attributes that make them effective for the fabrication of sensing devices. The aim of this review is to provide an update on the recent developments in the field of sensor devices made from atomically thin 2D materials.

Detection of single infrared photons in superconducting microstrips of 4 nm thick disordered Nb0.15Re0.85 has been investigated. Microstrips with a critical temperature of 5.15 K and widths from 1.0 to 2.5 μm have been fabricated by optical lithography. We demonstrate single photon detection sensitivity at 1.5 μm wavelength at a temperature of 1.79 K. By investigating the detection process at this temperature, we find that the current bias threshold is at 21% of the depairing current. This threshold is similar to what should be observed in typical amorphous superconductors, which confirms that ultrathin disordered Nb0.15Re0.85 is an interesting material for superconducting microstrip single photon detectors that operate above 1 K.

Three novel diketopyrrolopyrrole (DPP) based small molecules have been synthesized and characterized in terms of their chemical‐physical, electrochemical and electrical properties. All the molecules consist of a central DPP electron acceptor core symmetrically functionalized with donor bi‐thienyl moieties and flanked in the terminal positions by three different auxiliary electron‐acceptor groups. This kind of molecular structure, characterized by an alternation of electron acceptor and donor groups, was purposely designed to provide a significant absorption at the longer wavelengths of the visible spectrum: when analysed as thin films, in fact, the dyes absorb well over 800 nm and exhibit a narrow optical bandgap down to 1.28 eV. A detailed DFT analysis provides useful information on the electronic structure of the dyes and on the features of the main optical transitions. Organic field‐effect transistors (OFETs) have been fabricated by depositing the DPP dyes as active layers from solution: the different end‐functionalization of the dyes had an effect on the charge‐transport properties with two of the dyes acting as n‐type semiconductors (electron mobility up to 4.4 ⋅ 10 −2 cm 2 /V ⋅ s) and the third one as a p‐type semiconductor (hole mobility up to 2.3 ⋅ 10 −3 cm 2 /V ⋅ s). Interestingly, well‐balanced ambipolar transistors were achieved by blending the most performant n‐type and p‐type dyes with hole and electron mobility in the order of 10 −3 cm 2 /V ⋅ s