In Chan Baek

Core/shell silica-based in-situ microencapsulation: A self-templating method

Core/shell SiO2 and (RSiO1.5)(1-x)-(SiO2)x (R = alkyl) microcapsules were synthesized via a single-step O/W emulsion system using a self-templating method; the facile synthetic process provides an in-situ encapsulation route for a wide range of lipophilic functional compounds.

ZnSe colloidal nanoparticles synthesized by solvothermal method in the presence of ZrCl4.

The nanocrystalline ZnSe was synthesized from precursors of zinc acetate and Se powder in a high boiling trioctylphosphine (TOP), oleic acid, and ZrCl(4) by solvothermal method. The produced ZnSe nanoparticles showed gradual absorption edge shifting towards blue wavelength region as well as transformation of crystal phase from cubic to hexagonal with increasing ZrCl(4) concentrations in precursor solutions. The particle size calculated from XRD measurements for ZnSe nanoparticles was decreased with increasing ZrCl(4) concentrations for a reaction time of 240 min, from 6.5 nm to 5.1 nm whereas from TEM measurements it was 7.0 to 6.1 nm at 0.0 and 22.5 mol% of ZrCl(4), respectively. No trace of zirconium was found in solid ZnSe nanoparticles by SEM-EDS analysis but the atomic percentage of Se with respective to Zn was decreased with increasing ZrCl(4). The absorption edge blue shifting was explained on the basis of decreased particle size. The crystal phase transformation may be due to the combined effect of small internal energy difference between the two phases and the decrease of crystallite size.

The Effect of Acetic Acid in Synthesizing PbSe Quantum Dots by Hot Solution Chemical Process

PbSe, with a band gap in the mid-infrared and a samll effective mass, is an interesting material for optical and electrical applications in infrared region. Various colloidal synthetic routes for synthesizing PbSe quantum dot nanoparticles have been developed in the last couple of years. In this work, stable colloidal solutions containing crystalline PbSe particles in the order of 5-15 ㎚ were synthesized using different amount of acetic acid in high boiling coordinating solvents. The size and shape of PbSe nanoparticles was greatly influenced by coexistence of acetic acid in synthetic medium. It was observed by TEM that the shape of PbSe nanoparticles with different amount of acetic acid was changed from spherical to cube or star types.