We study electrical transport properties in exfoliated molybdenum disulfide (MoS) back-gated field effect transistors at low drain bias and under different illumination intensities. It is found that photoconductive and photogating effect as well as space charge limited conduction can simultaneously occur. We point out that the photoconductivity increases logarithmically with the light intensity and can persist with a decay time longer than 10 s, due to photo-charge trapping at the MoS/SiO interface and in MoS defects. The transfer characteristics present hysteresis that is enhanced by illumination. At low drain bias, the devices feature low contact resistance of [Formula: see text] ON current as high as [Formula: see text] 10 ON-OFF ratio, mobility of ∼1 cm V s and photoresponsivity [Formula: see text].

The high-bias electrical characteristics of back-gated field-effect transistors with chemical vapor deposition synthesized bilayer MoS 2 channel and Ti Schottky contacts are discussed. It is found that oxidized Ti contacts on MoS 2 form rectifying junctions with ≈0.3 to 0.5 eV Schottky barrier height. To explain the rectifying output characteristics of the transistors, a model is proposed based on two slightly asymmetric back-to-back Schottky barriers, where the highest current arises from image force barrier lowering at the electrically forced junction, while the reverse current is due to Schottkybarrier-limited injection at the grounded junction. The device achieves a photoresponsivity greater than 2.5 A W −1 under 5 mW cm −2 white-LED light. By comparing two-and four-probe measurements, it is demonstrated that the hysteresis and persistent photoconductivity exhibited by the transistor are peculiarities of the MoS 2 channel rather than effects of the Ti/MoS 2 interface.

Elemental carbon nanomaterials (ECNMs) are redox active agents that can be exploited to purposely modify the redox balance of cells. Both pro-or antioxidant properties have been reported. However, to the best of our knowledge, there are not comprehensive studies exploring both properties on the same material in view of a potential application in medicine. At the same time, the effect of the bulk structure on the pro/antioxidant properties is poorly known. Here, carbon nanoparticles (CNPs) derived by glucose with definite size and shape have been prepared, and their redox properties evaluated in cell free systems in the dark or following activation with a Near Infrared (NIR) laser beam (945 nm, 1.3 W/cm 2 ). We found that, when irradiated with NIR, CNPs efficiently generate heat and singlet oxygen ( 1 O2), a property that can be exploited for dual photo-thermal (PT)/ photodynamic (PD) therapy in cancer. On the other hand, in the absence of photo-activation, CNPs react with both oxidant (hydroxyl radicals) and antioxidant (glutathione) species. When tested on a murine macrophages cell line (RAW 264.7) CNPs were clearly antioxidant. Furthermore, albeit efficiently internalized, CNPs do not exert cytotoxic effect up to 80 µg/ml and do not exacerbate TNF-α-mediated inflammation. Overall, the results reported herein suggest that CNPs may represent a new class of safe nanomaterials with potential applications in medicine.

The metal assisted etching mechanism for Si nanowire fabrication, triggered by doping type and level and coupled with choice of metal catalyst, is still very poorly understood. We explain the different etching rates and porosities of wires we observe based on extensive experimental data, using a new empirical model we have developed. We establish as a key parameter, the tunneling through the space charge region (SCR) which is the result of the reduction of the SCR width by level of the Si wafer doping in the presence of the opposite biases of the p- and n-type wafers. This improved understanding should permit the fabrication of high quality wires with predesigned structural characteristics, which hitherto has not been possible.

The detection of quantal exocytic events from neurons and neuroendocrine cells is a challenging task in neuroscience. One of the most promising platforms for the development of a new generation of biosensors is diamond, due to its biocompatibility, transparency and chemical inertness. Moreover, the electrical properties of diamond can be turned from a perfect insulator into a conductive material (resistivity ∼mΩ·cm) by exploiting the metastable nature of this allotropic form of carbon. A 16-channels MEA (Multi Electrode Array) suitable for cell culture growing has been fabricated by means of ion implantation. A focused 1.2 MeV He+ beam was scanned on a IIa single-crystal diamond sample (4.5 × 4.5 × 0.5 mm3) to cause highly damaged sub-superficial structures that were defined with micrometric spatial resolution. After implantation, the sample was annealed. This process provides the conversion of the sub-superficial highly damaged regions to a graphitic phase embedded in a highly insulating diamond matrix. Thanks to a three-dimensional masking technique, the endpoints of the sub-superficial channels emerge in contact with the sample surface, therefore being available as sensing electrodes. Cyclic voltammetry and amperometry measurements of solutions with increasing concentrations of adrenaline were performed to characterize the biosensor sensitivity. The reported results demonstrate that this new type of biosensor is suitable for in vitro detection of catecholamine release.