Formation mechanism of monodisperse CdS particles from concentration solutions of Cd-EDTA complexes

Tadao Sugimoto, Grace E. Dirige, Atsushi Muramatsu

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57 Citations (Scopus)


The formation mechanism of monodisperse spherical CdS particles in a condensed homogeneous solution of Cd-EDTA complexes in the presence of thioacetamide (TAA), ammonium acetate, ammonia, and gelatin was studied. The monodisperse particles were formed through a consecutive process with an almost instantaneous nucleation and succeeding gradual growth without renucleation. The Cd-eDTA and TAA worked only as reservoirs of Cd2+ and S2- ions, but the rate-determining step of particle growth was found to be the dissociation process of the Cd-eDTA complexes and not of the TAA. Ammonia played a decisive role as a complexing agent at high concentrations of Cd(NH3)(n)2+, which could promptly release free Cd2+ ions, in promoting nucleation as well as growth even under a low supersaturation, and thus achieved excellent monodispersity by lowering the supersaturation below the critical level during their growth. The important role of CH3COONH4-NH3 as a powerful pH buffer for maintaining the activity of both NH3 and TAA was also proved. Moreover, size control of the final product was achieved in a range from 0.038 to 0.51 μm.

Original languageEnglish
Pages (from-to)444-456
Number of pages13
JournalJournal of Colloid And Interface Science
Issue number2
Publication statusPublished - 1996 Sep 25


  • CdS
  • EDTA
  • ammonia
  • galatin
  • monodispersed particles
  • size control
  • thioacetamide

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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