Stable Sulfuric Vapor Transport and Liquid Sulfur Growth on Transition Metal Dichalcogenides

Transition metal dichalcogenides (TMDs) are an emergent class of low-dimensional materials with growing applications in the field of nanoelectronics. However, efficient methods for synthesizing large monocrystals of these systems are still lacking. Here, we describe an efficient synthetic route for a large number of TMDs that were obtained in quartz glass ampoules by sulfuric vapor transport and liquid sulfur. Unlike the sublimation technique, the metal enters the gas phase in the form of molecules, hence containing a greater amount of sulfur than the growing crystal. We have investigated the physical properties for a selection of these crystals and compared them to state-of-the-art findings reported in the literature. The acquired electronic properties features demonstrate the overall high quality of single crystals grown in this work as exemplified by CoS2, ReS2, NbS2, and TaS2. This new approach to synthesize high-quality TMD single crystals can alleviate many material quality concerns and is suitable for emerging electronic devices

Understanding Self-Assembly of Porphyrin-Based SURMOFs: How Layered Minerals Can Be Useful

Porphyrin-based metal–organic frameworks on surfaces are a new class of planar materials with promising features for applications in chemical sensing, catalysis, and organic optoelectronics at nanoscale. Herein, we studied systematically a series of the SURMOFs assembled from variously <i>meso</i>-carboxyphenyl/pyridyl-substituted porphyrins and zinc acetate on template monolayers of graphene oxide via layer-by-layer deposition. This microscopically flat template can initiate the growth of macroscopically uniform SURMOF films exhibiting well-resolved X-ray diffraction. By applying the D’yakonov method, which has been previously used for the extraction of self-convolution of electron density in clay minerals, to the analysis of the experimental diffraction patterns of the SURMOFs, we determined the relation between the structure of porphyrin linkers and the geometry of packing motives in the films. We showed that the packing of the SURMOFs differs significantly from that of bulk powders of similar composition because of steric limitations imposed on the assembly in 2D space. The results of microscopic examination of the SURMOFs suggest that the type of metal-to-linker chemical bonding dictates the morphology of the films. Our method provides an enlightening picture of the interplay between supramolecular ordering and surface-directed assembly in porphyrin-based SURMOFs and is useful for rationalizing the fabrication of various classes of layered metal–organic frameworks on solids