K2Hg2Te3: Straightforward and Large-Scale Mercury-Flux Synthesis of a Small-Band-Gap Photoconducting Material.

K2Hg2Te3 was synthesized via a mercury-flux synthesis pathway. Single-crystal and powder X-ray diffraction reveal the compound to be isostructural to its lighter congener K2Hg2Se3, yet exhibiting enhanced photoconductivity and electrical conductivity of (several) orders of magnitude and a decreased thermal conductivity and band gap. In this report, we elaborate on the synthesis and properties of the novel ternary compound.

NOUF6 Revisited: A Comprehensive Study of a Hexafluoridouranate(V) Salt.

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.

Changes in the structural dimensionality of selenidostannates in ionic liquids: formation, structures, stability, and photoconductivity.

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.

Terahertz Brewster lenses.

Typical lenses suffer from Fresnel reflections at their surfaces, reducing the transmitted power and leading to interference phenomena. While antireflection coatings can efficiently suppress these reflections for a small frequency window, broadband antireflection coatings remain challenging. In this paper, we report on the simulation and experimental investigation of Brewster lenses in the THz-range. These lenses can be operated under the Brewster angle, ensuring reflection-free transmission of p-polarized light in an extremely broad spectral range. Experimental proof of the excellent focusing capabilities of the Brewster lenses is given by frequency and spatially resolved focus plane measurements using a fiber-coupled THz-TDS system.

Terahertz time-domain spectroscopy for monitoring the curing of dental composites.

We apply terahertz (THz) time-domain spectroscopy for monitoring the curing process of three different light-curing dental composites. Exact knowledge of the sample thickness is required for a precise determination of the THz dielectric parameters, as the materials exhibit shrinkage when they are cured. We find very small but significant changes of the THz refractive index and absorption coefficient during stepwise light exposure. The changes in the refractive index are correlated with changes in the density of the materials. Furthermore, the refractive index and the sample thickness are found to give the most reliable result for monitoring the curing process of the dental composites.