title: "Amorphous nickel sulfide" is hydrated nanocrystalline nis with a core-shell structure.
abstract: The application of a range of experimental techniques shows that "amorphous nickel sulfide" (the material precipitated from aqueous solutions of Ni(II) salts and S(II-) under ambient conditions) is actually a hydrated nanoparticulate material with an approximate formula NiS.1.5H(2)O. The particles comprise a crystalline, anhydrous core (diameter ca. 1-3 nm) with the millerite (NiS) structure, surrounded by a hydrated shell phase. The materials prepared under acidic conditions (pH = 3 and 5) transform with age to form polydymite (Ni(3)S(4)) and heazlewoodite (Ni(3)S(2)), while materials prepared at pH = 7 and 9 do not undergo this transformation. At pH = 12, the preparation procedure yields NiAs-type NiS as a metastable phase.
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, Wales.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Huang
authors.forename: Kenneth D M
authors.initials: KD
authors.lastname: Harris
authors.forename: Elisa
authors.initials: E
authors.lastname: Lopez-Capel
authors.forename: David A C
authors.initials: DA
authors.lastname: Manning
authors.forename: David
authors.initials: D
authors.lastname: Rickard