title: Synthesis and properties of water-soluble core-shell-shell silica-CdSe/CdS-silica nanoparticles.
abstract: This paper describes the synthesis of highly water-soluble and fluorescent core-shell-shell silica-CdSe/CdS-silica nanoparticles (CSS silica-QDs-silica NPs). We used cadmium nitrate and 1,1-dimethyl-2-selenourea precursors to synthesize CdSe quantum dots (QDs) in aqueous solution under simultaneous illumination with a diode-pumped solid state green laser and a Xe-Hg lamp. After passivation of the CdSe QDs with CdS, the CdSe/CdS QDs were then conjugated covalently to (3-mercaptopropyl)trimethoxysilane (MPS); we call these nanoparticles "MPS-QDs". We mixed the MPS-QDs with tetraethoxysilane (TEOS), ethanol, and NH3. By controlling the concentrations of the reagents, the stirring speed, and the reaction time, we synthesized CSS silica-QDs-silica NPs having sizes ranging from 75 to 190 nm. The incubation time for preparing the MPS-QDs and their concentrations are important parameters in determining the morphologies of the CSS silica-QDs-silica NPs. When we mixed 50 nM MPS-QDs, 1.1 mM TEOS, and 78 mM NH3 and reacted them at a stirring speed of 750 rpm, we obtained 85-nm-diameter CSS silica-QDs-silica NPs having a QD shell thickness of about 20 nm. The CSS silica-QDs-silica NPs provide a strong photoluminescence intensity (quantum yield 88%) and exhibit enhanced stability both photochemically and in high-conductivity media (e.g., 1.0 M NaCl).
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei.
authors.forename: Yang-Wei
authors.initials: YW
authors.lastname: Lin
authors.forename: Chi-Wei
authors.initials: CW
authors.lastname: Liu
authors.forename: Huan-Tsung
authors.initials: HT
authors.lastname: Chang
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D003460:Crystallization / Q000379:methods; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D012995:Solubility; D013440:Sulfides / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D014867:Water; D012822:Silicon Dioxide; C058667:cadmium selenide