title: Precipitation, stabilization and molecular modeling of ZnS nanoparticles in the presence of cetyltrimethylammonium bromide.
abstract: ZnS nanoparticles were precipitated in aqueous dispersions of cationic surfactant cetyltrimethylammonium bromide (CTAB). The sphere radii of ZnS nanoparticles calculated by using band-gap energies steeply decreased from 4.5 nm to 2.2 nm within CTAB concentrations of 0.4-1.5 mmol L(-1). Above the concentration of 1.5 mmol L(-1), the radii were stabilized at R=2.0 nm and increased up to R=2.5 nm after 24 h. The hydrodynamic diameters of CTAB-ZnS structures observed by the dynamic light scattering (DLS) method ranged from 130 nm to 23 nm depending on CTAB concentrations of 0.5-1.5 mmol L(-1). The complex structures were observed by transmission electron microscopy (TEM). At the higher CTAB concentrations, ZnS nanoparticles were surrounded by CTA(+) bilayers forming positively charged micelles with the diameter of 10nm. The positive zeta-potentials of the micelles and their agglomerates were from 16 mV to 33 mV. Wurtzite and sphalerite nanoparticles with R=2.0 nm and 2.5 nm covered by CTA(+) were modeled with and without water. Calculated sublimation energies confirmed that a bilayer arrangement of CTA(+) on the ZnS nanoparticles was preferred to a monolayer.
authors.affiliation: Department of Analytical Chemistry and Material Testing, VŠB-Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava-Poruba, Czech Republic. petr.praus@vsb.cz
authors.forename: Petr
authors.initials: P
authors.lastname: Praus
authors.forename: Richard
authors.initials: R
authors.lastname: Dvorský
authors.forename: Petra
authors.initials: P
authors.lastname: Horínková
authors.forename: Miroslav
authors.initials: M
authors.lastname: Pospíšil
authors.forename: Petr
authors.initials: P
authors.lastname: Kovář
mesh_terms: D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D011232:Chemical Precipitation; D008027:Light; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D012542:Scattering, Radiation; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D019287:Zinc Sulfate / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D013501:Surface-Active Agents; D019287:Zinc Sulfate; D000077286:Cetrimonium