Preparation of Metal Sulfides from Chelates

Institute for Advanced Materials Processing, Tohoku University, Sendai, Japan 

Chiu prepared monodisperse crystalline particles of metal sulfides, such as lead sulfide (PbS cubes 100 A) (I), cupric sulfide (CuS hexagonal bipyramids 200 A) (2), and zinc sulfide (ZnS multifaceted spheres 0.1-0.4 p,m) (3) by introducing hydrogen sulfide gas into dilute acidic solutions of the ethylenediamine tetraacetic acid (EDTA) complexes of the corresponding metal ions (10 4-10-1 mol dm-3) for several minutes at room temperature. 

In the condensed chelate systems, many kinds of chelating agents were used, such as ethylenediamiiie-/V,/V,/V, /V -tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), /-aspartic acid (AA), trimethylenediamine (TMD), /V,/V-dimethylethylenedi-amine (DMED), diethylenetriamine (DETA), triethylenetetraamine (TETA), and t ris(2-aminoethyl)amine (TAEA) (6). The chelating agents used are listed in Table 3.2.1. 

Note The chelating agents marked with an asterisk ( ), DMED and AA, were used only for ihe formation of CuS. 

If one chooses a chelating agent with a relatively high stability constant, such as EDTA, one may find some ideal separation of nucleation and growth stages as a decisive prerequisite for monodispersed particles formation, since a drastic change of supersaturation can be expected in a system with metal ions around the stoichio- 

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