Reducing the size of a material, from a bulk solid to a nanomaterial, may lead to drastic changes of various properties including reactivity and optical properties. Chemical reactivity is often increased due to the nanomaterial’s higher effective surface area, while confinement and geometric effects lead to systematic changes in optical properties. Here, we investigate the size-dependent properties of Ni2P2S6 nanosheets that were obtained from liquid phase exfoliation in N-cyclohexyl-2-pyrrolidone. The as-obtained stock dispersion was size-selected by liquid cascade centrifugation resulting in fractions with distinct size and thickness distributions, as quantified by statistical atomic force microscopy. Raman, TEM, XRD, and XPS characterization revealed that the exfoliated flakes have good crystallinity and high structural integrity across all sizes. The optical extinction and absorbance spectra systematically change with the lateral dimensions and layer number, respectively. Linking these changes to nanosheet dimensions allows us to establish quantitative metrics for size and thickness from optical properties. To gain insights into the environmental stability, extinction/absorbance behavior was followed as a function of time at different storage temperatures. Degradation is observed following first-order kinetics, and activation energies were extracted from the temperature dependent data. The decomposition is due to oxidation which appears to occur both at edges and on the basal plane.

Solution‐processed, low cost thin films of layered semiconductors such as transition metal dichalcogenides (TMDs) are potential candidates for future printed electronics. Here, n‐type electrolyte‐gated transistors (EGTs) based on porous WS2 nanosheet networks as the semiconductor are demonstrated. The WS2 nanosheets are liquid phase exfoliated to form aqueous/surfactant stabilized inks, and deposited at low temperatures (T < 120 °C) in ambient atmosphere by airbrushing. No solvent exchange, further additives, or complicated processing steps are required. While the EGTs are primarily n‐type (electron accumulation), some hole transport is also observable. The EGTs show current modulations > 104 with low hysteresis, channel width‐normalized on‐conductances of up to 0.27 µS µm−1 and estimated electron mobilities around 0.01 cm2 V−1 s−1. In addition, the WS2 nanosheet networks exhibit relatively high volumetric capacitance values of 30 F cm−3. Charge transport within the network depends significantly on the applied lateral electric field and is thermally activated, which supports the notion that hopping between nanosheets is a major limiting factor for these networks and their future application.

For all-printed circuits, the critical device dimensions, in particular, the channel length in lateral field-effect transistors (FETs), are limited by the printing resolution and alignment accuracy. In contrast, the channel length in vertical electrolyte-gated transistors (VEGTs) is mainly defined by the film thickness and can be easily scaled down to less than 100 nm to achieve high current densities. For practical VEGTs, the printed semiconductor must be highly porous to enable efficient electrolytegating by ion penetration. Here, we use aerosol-jet (AJ)-printed layers of polymer-sorted (6,5) single-walled carbon nanotubes with film thicknesses from less than 50 nm to several hundred nanometers as the semiconducting layer sandwiched between evaporated (gold) or printed (silver nanoparticle) metal electrodes and gated by an ionic-liquid-based ion gel. Vertical charge transport in the obtained three-dimensional nanotube networks is confirmed via conductive AFM measurements. The nanotube network VEGTs exhibit transfer characteristics with good on/off ratios and high on-conductances. The effective gating of the semiconducting nanotubes throughout the entire active area of several hundred μm 2 is corroborated by in situ Raman spectroscopy. The overall transistor performance scales with film thickness and electrode overlap and is comparable to photolithographically structured lateral electrolyte-gated transistors with 2 μm short channels. VEGTs could thus be a viable replacement of printed lateral FETs that require too much space for the desired drive currents.

The optical field generated by a nanoplasmonic probe is revealed in tip-enhanced Raman spectroscopy – TERS – experiments. The TERS intensity profile of nano-objects smaller than the probe’s apex has a donut-like shape which resembles the magnitude of the field generated by a point-dipole source, being well described by the Dyadic Green’s function. Having prior knowledge on the excitation field generated by the TERS probe, we measured the width of shear solitons caused by lattice reconstruction in low-angle twisted bilayer graphene, a prominent platform for twistronics, and the extend of defect-induced light emission from graphene edges.

In recent years, various functionalization strategies for transition-metal dichalcogenides have been explored to tailor the properties of materials and to provide anchor points for the fabrication of hybrid structures. Herein, new insights into the role of the surfactant in functionalization reactions are described. Using the spontaneous reaction of WS 2 with chloroauric acid as a model reaction, the regioselective formation of gold nanoparticles on WS 2 is shown to be heavily dependent on the surfactant employed. A simple model is developed to explain the role of the chosen surfactant in this heterogeneous functionalization reaction. The surfactant coverage is identified as the crucial element that governs the dominant reaction pathway and therefore can severely alter the reaction outcome. This study shows the general importance of the surfactant choice and how detrimental or beneficial a certain surfactant can be to the desired functionalization.