Two-dimensional MoS 2 is a promising material for nanoelectronics and 9 catalysis, but its potential is not fully exploited since proper control of its multiple phases 10 (H, T, ZT) and electronic properties is lacking. In this theoretical study, alloying is 11 proposed as a method to stabilize the MoS 2 T-phase. In particular, MoS 2 is alloyed with 12 another material that is known to exist in a monolayer MX 2 T-structure, and we show

Memristive devices based on electrochemical resistive switching effects have been proposed as promising candidates for in-memory computing and for the realization of artificial neural networks. Despite great efforts toward understanding the nanoionic processes underlying resistive switching phenomena, comprehension of the effect of competing redox processes on device functionalities from the materials perspective still represents a challenge. In this work, we experimentally and theoretically investigate the concurring reactions of silver and moisture and their impact on the electronic properties of a single-crystalline ZnO nanowire (NW). A decrease in electronic conductivity due to surface adsorption of moisture is observed, whereas, at the same time, water molecules reduce the energy barrier for Ag+ ion migration on the NW surface, facilitating the conductive filament formation. By controlling the relative humidity, the ratio of intrinsic electronic conductivity and surface ionic conductivity can be tuned to modulate the device performance. The results achieved on a single-crystalline memristive model system shed new light on the dual nature of the mechanism of how moisture affects resistive switching behavior in memristive devices.

Resistive switching memory operation is generally described in terms of formation and rupture of a conductive filament connecting two metal electrodes. Although this model was reported for several device types, its applicability is not guaranteed to all of them. On the basis of density functional theory calculations, we propose a novel switching mechanism suitable to nanowire-based resistive switching memories. For thick devices in particular, the current is highly unlikely to flow through a metallic filament connecting the electrodes. We demonstrate that in the case of ZnO nanowires metal adatoms, spread on the nanowire surface, locally dope the insulating oxide allowing surface conductance even for small metal concentrations.

Nanoporous graphene was proposed as an efficient material for reverse osmosis water desalination membranes because it allows water molecules to pass at high flux while rejecting hydrated salt ions. Nevertheless, from an experimental point of view it is still difficult to control the pore size. A scalable method to generate pores is urgently required for the diffusion of this technology. We propose, by theoretical calculations, an innovative and scalable strategy to better control the dimension of the pores in graphenebased membranes by reduction of single-layer graphene oxide (GO). The latter is first annealed at a controlled mild temperature to induce the aggregation of its randomly distributed oxygen-containing functional groups into small nanometric clusters. The layer then undergoes a high-temperature reducing treatment that causes the desorption of the functional groups along with carbon removal only in the oxidized areas, producing subnanometric pores while leaving unchanged the remaining pristine graphene areas.

Gas filtration by means of membranes is becoming increasingly important for industrial processes due to its low cost. In particular, membranes can be applied to separate methane in natural gas from pollutants such as hydrogen sulfide and carbon dioxide. The recent advent of nanoporous graphene as material for membranes helped to overcome the current problems of polymeric membranes, namely the permeability/selectivity tradeoff. However, the factors that determine gas filtration through nanoporous graphene are not completely clear yet. In this work, we show that pore size, shape and functionalization severely affect the selectivity of the membrane toward CO 2 and H 2 S with respect to CH 4 . We identified that the critical diameter of circular pore for the separation of contaminants from methane with graphene membranes is 5.90 Å. An elliptical pore is discovered to select gas species having similar sizes on the basis of their shape. The more elongated CO 2 is allowed to pass though the pore while the more spherical H 2 S and CH 4 are rejected. Finally, the gas-membrane interactions are found to decisively affect the filtration performances. Functionalization with hydroxyl groups led to a higher permeability of the gas species with polar bonds while keeping an excellent selectivity.