Monolayers of transition-metal dichalcogenides such as WSe 2 have become increasingly attractive due to their potential in electrical and optical applications. Because the properties of these 2D systems are known to be affected by their surroundings, we report how the choice of the substrate material affects the optical properties of monolayer WSe 2 . To accomplish this study, pump-density-dependent micro-photoluminescence measurements are performed with time-integrating and time-resolving acquisition techniques. Spectral information and power-dependent mode intensities are compared at 290K and 10K for exfoliated WSe 2 on SiO 2 /Si, sapphire (Al 2 O 3 ), hBN/Si 3 N 4 /Si, and MgF 2 , indicating substrate-dependent appearance and strength of exciton, trion, and biexciton modes. Additionally, one CVD-grown WSe 2 monolayer on sapphire is included in this study for direct comparison with its exfoliated counterpart. Time-resolved micro-photoluminescence shows how radiative decay times strongly differ for different substrate materials. Our data indicates exciton-exciton annihilation as a shortening mechanism at room temperature, and subtle trends in the decay rates in correlation to the dielectric environment at cryogenic temperatures. On the measureable time scales, trends are also related to the extent of the respective 2D-excitonic modes' appearance. This result highlights the importance of further detailed characterization of exciton features in 2D materials, particularly with respect to the choice of substrate.

In situ transformations of selenidostannate frameworks in ionic liquids (ILs) were initiated by treatment of the starting phase K2[Sn2Se5] and the consecutive reaction products by means of temperature increase and/or amine addition. Along the reaction pathway, the framework dimensionalities of the five involved selenidostannate anions develop from 3D to 1D and back, both in top-down and bottom-up style. Addition of ethane-1,2-diamine (en) led to the reversion of the 2D→1D step from 2D-{[Sn24Se56](16-)} to 1D-{[Sn6Se14](4-)}. As rationalized by DFT investigations, the 2D anion is thermodynamically favored. Photoconductivity measurements reveal that all samples show Schottky contact behavior with absolute thresholds below 10 V. One of the samples exhibits conductive states within the energy range of visible photons.

K 2 Hg 2 Se 3 , a new photoconducting material with a direct band gap around 1.4 eV, was obtained in nearly quantitative yields and large scale (50 g per batch) by means of solvothermal treatment of a corresponding solid. The compound comprises covalently linked selenidomercurate columns that accommodate potassium counterions. Composition and structure allow for a specific combination of optoelectronic, photophysical, and thermoelectric properties, which initiates a systematic material development within this family of compounds.T he search for innovative materials for electronic applications is an enormous stimulus for contemporary chemical and physical research activities. A large portion of according materials are found within oxides and chalcogenides of fourth and fifth period metals.

Terahertz time-domain spectroscopy (THz TDS) is a well-known tool for material\ud analysis in the terahertz frequency band. One crucial system component in every time-domain\ud spectrometer is the delay line which is necessary to accomplish the sampling of the electric\ud field over time. Despite the fact that most of the uncertainty sources in TDS have been\ud discussed, the delay line uncertainty has not been considered in detail. We model the impact\ud of delay line uncertainty on the acquired THz TDS data. Interferometric measurements of the\ud delay line precision and THz time-domain data are used to validate the theoretical model

We have synthesized NOUF6 by direct reaction of NO with UF6 in anhydrous HF (aHF). Based on the unit cell volume and powder diffraction data, the compound was previously reported to be isotypic to O2 PtF6 , however, detailed structural data, such as the atom positions and all information that can be derived from those, were unavailable. We have therefore investigated the compound by using single-crystal and powder X-ray diffraction, IR, Raman, NMR, EPR, and photoluminescence spectroscopy, magnetic measurements, as well as chemical analysis, density determination, and quantum chemical calculations.