In control! Ag2S nanocrystals of predictable size and shape were synthesized from the precursor Ag(SCOPh) in the presence of an amine. Careful tuning of several parameters, such as the reaction temperature and the ratio of amine to precursor, led to Ag2S nanocrystals of varying morphology (red: nanocubes; blue: faceted nanocrystals; yellow: nanorods) and size. x=particle size. HDA=hexadecylamine.

Monodispersed copper sulfide nanocrystals were synthesized via the decomposition of an air-stable precursor, copper (I) thiobenzoate (CuTB), in the presence of dodecanethiol (DDT). We discover that, by varying the stabilizing agent used (trioctylphosphine or tributylphosphite), we can selectively generate phase-pure roxbyite nanoplates (Cu 1.75 S) or chalcocite faceted nanocrystals (Cu 2 S). We also demonstrate that, under suitable conditions, the roxbyite nanoplates can be forced to grow only in two dimensions, with an aspect ratio (diameter/thickness) tunable between 2.3 and 4.1. To the best of our knowledge, this is the first report for making nanocrystalline copper sulfide with such aspect ratio tunability. Temperature and the [DDT]/[CuTB] ratio were identified to be the important factors for controlling the size of the nanocrystals. To gain more insight to the mechanisms of phase-selective control, we attempted a series of controlled experiments and DFT calculations. It appears that the precursor can undergo two competitive pathways, leading to seeds, and thus the growth, of different crystal phases. This work thus demonstrates a general approach to phase-selective nanocrystals engineering whereby the kinetics of decomposition of a chosen precursor is readily manipulated using activating or stabilizing agents.

Hybrid composites of PbS nanoparticles embedded in sulfonated polystyrene matrixes were prepared without other added capping agent in the random ionomer. The nanocomposites were found to exhibit photoluminescence in both the near-infrared and visible regions. The infrared luminescence was tunable in the range 1100-1500 nm via quantum size effect. XRD, TEM, UV-vis, FTIR, DSC, and XPS techniques were employed to investigate the size, shape, morphology, absorption, and thermal properties as well as the formation mechanism of nanoparticles in the ionomer matrix. The unique microstructure of the sulfonated polystyrene ionomer was found to provide a confined medium for the formation of nanoparticles. The -SO 3groups acted as the coordination sites for Pb 2+ ion aggregation, PbS nanoparticles were then successfully grown in situ at these sites with a supply of S 2from thioacetamide. The sizes and shapes of the PbS nanoparticles produced were controllable by varying the sulfonate content of the polymer and the initial feed concentration of Pb 2+ ions. The average size of PbS nanoparticles was estimated to be 5-8 nm, with size dispersity of ∼10-12%. Some PbS nanorods, with an average diameter of 3.5 nm, were formed at higher Pb/SO 3 H feed ratios.