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Although many of the layered metal chalcogenides, such as MoS2, are well-studied, some other chalcogenides have received less attention by comparison. In particular, there has been an emerging interest in vanadium tetrasulfide (VS4), which displays useful properties as a component of hybrids. However, the synthetic methods and characteristics of individual VS4 are not yet well defined, and there is no report on its solution processability. Here we have synthesized VS4 by a simple and fast direct reaction between elements. Reinvestigation of the VS4 crystal structure yielded more precise atomic coordinates and interatomic distances, thereby confirming the crystallization of VS4 in the monoclinic C2/c group and its quasi-1D chainlike structure. As the chains in VS4 are only bonded by weak van der Waals forces, we further demonstrate that bulk VS4 may be ultrasonically dispersed in appropriate solvents to form colloids, similarly to the layered chalcogenides. VS4 particles in colloids retain their phase identity and rod-shaped morphology with lengths in the range of hundreds of nanometers. Isopropanol dispersion exhibited the highest concentration and stability, which was achieved owing to the repulsion caused by high negative charges on the edges of the particles.

Phenomena preceding precipitation of gold(i) sulfide in the reaction of aqueous tetrachloroauric acid with sodium sulfide have been studied applying several time-resolved in situ techniques. As can be deduced from UV-vis absorption spectroscopy, soluble species ("pre-nucleation clusters") emerge within several seconds and slightly change with time; the spectra, along with the previous data for the immobilized products, are indicative of disordered matter with Au(I)-S bonding and the gap of about 1.5 eV. In situ tapping-mode atomic force microscopy (AFM) directly imaged "soft" droplet-like species from 20-50 nm to about 200 nm in the lateral size and the continuous film condensed on the highly oriented pyrolytic graphite (HOPG) support. Small-angle X-ray scattering (SAXS) revealed quasi-particles ("liquid clusters") growing to about 12 nm for 30 min, and slowly afterwards. Dynamic light scattering (DLS) was preferentially due to the larger species, although the liquid clusters within 20 nm comprise more than 80% of the total volume of the fluid products. The entities, which exist in solution for many hours before sudden gold sulfide sedimentation, are considered as "dense liquid" intermediates involved in a non-classical nucleation pathway.

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We have determined the solubilization and crystallization fields of KNO3 for simple (Tergitol NP-4 and AOT) and mixed (Tergitol NP-4 + AOT) microemulsions at 35 °C, depending on water content and concentration of KNO3. An increase in the content of AOT in mixed microemulsions leads to widening of the solubilization field, but the crystallization field narrows up to complete disappearance (in simple microemulsions of AOT). Fourier transform-infrared spectroscopy, photon–correlation spectroscopy, and flame photometry were used to determine the rate of water evaporation (2.6–7.4 μL/min), hydrodynamic diameter of micelles (4.3–10 nm), and the content of water and K+ and Na+ ions in the studied microemulsions at different stages of evaporation crystallization of KNO3. In simple microemulsions of Tergitol NP-4 crystallization begins well before that in mixed microemulsions; in mixed microemulsions the beginning of crystallization requires higher supersaturation (up to 13 M) compared to simple microemulsions (∼4 M at initial solubilization capacity of 0.5 vol %). In accordance with the Gibbs–Thomson (Kelvin) theory, high supersaturations suggest that in mixed micelles cores of smaller sizes are formed. During crystallization, micelles with KNO3 solution coexist with KNO3 crystals. The function of micelles is to supply “building material” for their growth. Numerical simulation with the help of direct optimization showed that in mixed micelles at low water contents, Na+ ions are stronger bound with AOT–, owing to which Na+ ions occur only as impurities in powders.