gree of amorphous character. This would be expected as the deposition occurs at room temperature and the presence of any crystalline material is in itself remarkable. Different polymorphs have differing optical properties; hence this could provide a simple route to a generally inaccessible material with potentially interesting applications. Scanning electron microscopy (SEM) revealed the films (14 days deposition) were composed of nanosized HgS spheres, from 20 to 250 nm in diameter (Fig. 3). The nanodimensions of the particles could explain the stability of the b-polymorph film, as small particles can often exist in energetically unfavorable crystal phases.[20] Absorption spectroscopy on the same film showed an onset of absorption at ca. 1 eV with an excitonic feature at ca. 1.3 eV (Fig. 2b). Although this does not fit with any theoretical data, other studies have shown that band-edge measurement of HgS materials do not correlate with predicted bandgaps.[21]In conclusion, we have prepared a novel mercury(II) dithiocarbamate complex with an eight-membered ring structure. The molecule has been used as a room-temperature precursor to a metastable phase of mercury sulphide not normally accessible via low-temperature reaction pathways. ExperimentalIn a typical synthesis, [Hg(S 2 CNMe(EtPh)) 2 ] 2 was prepared by dissolving 1.95 g (6.1 10 ±3 M) mercury acetate in 150 mL ethanol, followed by filtration. To this was added dropwise a mixture of carbon disulfide (0.8 mL, 0.012 M) and N-methylphenethylamine (2 ml, 0.012 M) in 50 mL ethanol, producing an immediate white precipitate. After 4 h stirring, the precipitate was filtered, air dried, and redissolved in 50 mL dichloromethane. Storage at 4 C resulted in yellow needle-like crystals, the single-crystal X-ray structure (120 K) of which is shown in Figure 1. It is noteworthy that the precursor started to decompose in solution and a black material was observed (HgS). Once isolated, the yellow crystals were indefinitely stable at room temperature. To produce a b-HgS thin film, 0.05 g of [Hg(S 2 CNMe(EtPh)) 2 ] 2 was dissolved in 10 mL acetone producing a optically clear colorless solution, into which a glass substrate was placed vertically.

Particles of amorphous calcium carbonate (ACC), formed in situ from calcium chloride by the slow release of carbon dioxide by alkaline hydrolysis of dimethyl carbonate in water, are stabilized against coalescence in the presence of very small amounts of double hydrophilic block copolymers (DHBCs) composed of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blocks. Under optimized conditions, spherical particles of ACC with diameters less than 100 nm and narrow size distribution are obtained at a concentration of only 3 ppm of PEO-b-PAA as additive. Equivalent triblock or star DHBCs are compared to diblock copolymers. The results are interpreted assuming an interaction of the PAA blocks with the surface of the liquid droplets of the concentrated CaCO3 phase, formed by phase separation from the initially homogeneous reaction mixture. The adsorption layer of the block copolymer protects the liquid precursor of ACC from coalescence and/or coagulation.