In-situ interface self-assemblies of nanocrystalline Ag2E (E = S, Se, or Te) via chalcogen directional transfer agents

Nanocrystalline Ag2E (E = S, Se, or Te) was interface self-assembled in-situ in the heterogeneous microphase via the reaction of aqueous AgNO3 and R=E (R = PPh3, PBu3, PCy3 or Py; E = S, Se, or Te) toluene solution at room temperature. Chalcogen directional transfer agents R=E were prepared by refluxing in toluene solution for 12 h. The compositions of as-prepared products were characterized by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The atomic ratios of Ag to S, Se or Te, measured by inductively coupled plasma (ICP) spectroscopy, were 1.98:1, 2.08:1 and 2.13:1, respectively. The morphologies of products were confirmed by transmission electron microscopy (TEM). UV-Visible spectroscopy was used to record the absorption of Ag2E nanocrystallites after removal of the passivated molecules at high temperature (> 500 degreesC). The thermal stability of Ag2E particles passivated by R=E (R = PPh3, PBu3, PCy3 or Py) molecules was studied using thermal gravimetric analysis (TGA). The possible mechanism of nanocrystalline silver chalcogenide self-assembly is discussed.