Evaluating strain and doping of Janus MoSSe from phonon mode shifts supported by DFT calculations.

With the study of Janus monolayer transition metal dichalcogenides, in which one of the two chalcogen layers is replaced by another type of chalcogen atom, research on two-dimensional materials is advancing into new areas. Yet only little is known about this new kind of material class, mainly due to the difficult synthesis. In this work, we synthesize MoSSe monolayers from exfoliated samples and compare their Raman signatures with density functional theory calculations of phonon modes that depend in a nontrivial way on doping and strain.

Structural Insights into Hysteretic Spin-Crossover in a Set of Iron(II)-2,6-bis(1H-Pyrazol-1-yl)Pyridine) Complexes.

Bistable spin-crossover (SCO) complexes that undergo abrupt and hysteretic (ΔT ) spin-state switching are desirable for molecule-based switching and memory applications. In this study, we report on structural facets governing hysteretic SCO in a set of iron(II)-2,6-bis(1H-pyrazol-1-yl)pyridine) (bpp) complexes - [Fe(bpp-COOEt) ](X) ⋅CH NO (X=ClO , 1; X=BF , 2). Stable spin-state switching - T =288 K; ΔT =62 K - is observed for 1, whereas 2 undergoes above-room-temperature lattice-solvent content-dependent SCO - T =331 K; ΔT =43 K.

Large-Area, Two-Dimensional MoS Exfoliated on Gold: Direct Experimental Access to the Metal-Semiconductor Interface.

Two-dimensional semiconductors such as MoS are promising for future electrical devices. The interface to metals is a crucial and critical aspect for these devices because undesirably high resistances due to Fermi level pinning are present, resulting in unwanted energy losses. To date, experimental information on such junctions has been obtained mainly indirectly by evaluating transistor characteristics.

Towards field-effect controlled graphene-enhanced Raman spectroscopy of cobalt octaethylporphyrin molecules.

During the last decade graphene-enhanced Raman spectroscopy has proven to be a powerful tool to detect and analyze minute amounts of molecules adsorbed on graphene. By using a graphene-based field-effect device the unique opportunity arises to gain a deeper insight into the coupling of molecules and graphene as graphene's Fermi level can be controlled by the transistor`s gate voltage. However, the fabrication of such a device comes with great challenges because of contaminations stemming from processing the device inevitably prevent direct adsorption of the molecules onto graphene rendering it unsuitable for field-effect controlled graphene-enhanced Raman spectroscopy measurements/experiments.

Apparent differences between single layer molybdenum disulphide fabricated via chemical vapour deposition and exfoliation.

Innovative applications based on two-dimensional solids require cost-effective fabrication processes resulting in large areas of high quality materials. Chemical vapour deposition is among the most promising methods to fulfill these requirements. However, for 2D materials prepared in this way it is generally assumed that they are of inferior quality in comparison to the exfoliated 2D materials commonly used in basic research.

The effect of elevated temperatures on excitonic emission and degradation processes of WS monolayers.

Controlled heating experiments in an inert environment have been performed on WS2 monolayers, in order to clarify the conflicting reports on the high-temperature photoluminescent response of 2D TMDs. We find that in contrast to some previous results on both WS2 and MoS2, the photoluminescent intensity shows a consistent reduction above room temperature. This is accompanied by an almost linear redshift of the peak maximum, and a nearly linear increase in the peak width, which is attributed to an enhanced interaction with optical phonons.

Electron Irradiation of Metal Contacts in Monolayer MoS Field-Effect Transistors.

Metal contacts play a fundamental role in nanoscale devices. In this work, Schottky metal contacts in monolayer molybdenum disulfide (MoS) field-effect transistors are investigated under electron beam irradiation. It is shown that the exposure of Ti/Au source/drain electrodes to an electron beam reduces the contact resistance and improves the transistor performance.

Perforating Freestanding Molybdenum Disulfide Monolayers with Highly Charged Ions.

Porous single-layer molybdenum disulfide (MoS) is a promising material for applications such as DNA sequencing and water desalination. In this work, we introduce irradiation with highly charged ions (HCIs) as a new technique to fabricate well-defined pores in MoS. Surprisingly, we find a linear increase of the pore creation efficiency over a broad range of potential energies.

Highly active single-layer MoS catalysts synthesized by swift heavy ion irradiation.

Two-dimensional molybdenum-disulfide (MoS2) catalysts can achieve high catalytic activity for the hydrogen evolution reaction upon appropriate modification of their surface. The intrinsic inertness of the compound's basal planes can be overcome by either increasing the number of catalytically active edge sites or by enhancing the activity of the basal planes via a controlled creation of sulfur vacancies. Here, we report a novel method of activating the MoS2 surface using swift heavy ion irradiation.

High affinity peptide inhibitors of the hepatitis C virus NS3-4A protease refractory to common resistant mutants.

Hepatitis C virus (HCV) NS3-4A protease is essential for viral replication. All current small molecular weight drugs against NS3-4A are substrate peptidomimetics that have a similar binding and resistance profile. We developed inhibitory peptides (IPs) capping the active site and binding via a novel "tyrosine" finger at an alternative NS3-4A site that is of particular interest for further HCV drug development.