Colloidal CdSe Nanocrystals from Tri-n-Octylphosphine: Part II: Control of Growth Rate for High Quality and Large-Scale Production by Tuning Cd-to-Se Stoichiometry

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DOIResolve DOI: http://doi.org/10.1166/jnn.2005.123
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TypeArticle
Journal titleJournal of Nanoscience and Nanotechnology
Volume5
Issue4
Pages669681; # of pages: 13
SubjectCdSe nano-particles; growth kinetics; non-resonant stokes shift; photoluminescent properties; semi-conducting nano-crystals; synthesis and characterization; zero-growth rate
AbstractColloidal CdSe nanocrystals were synthesized in reaction media consisting of tri-n-octylphosphine (TOP) without addition of other species; the single-step approach used cadmium oxide (CdO) and TOPSe as Cd and Se sources, respectively. The temporal evolution of the optical properties of the growing TOP-capped CdSe nanocrystals was monitored for a couple of hours, showing that there are two distinguishable stages of growth: an early stage (less than 5 minutes) and a later stage; the growth kinetics of the two stages is a function of the Cd-to-Se precursor molar ratios. A rational choice of 2�6Cd-to-1Se molar ratio was found, based on the temporal evolution of the photoluminescent (PL) efficiency (studied as PL intensity and sensitivity to the media of dispersion, and non-resonant Stokes shifts). For a 2Cd-to-1Se synthesis, the growth in size was slow in the early stages and became fast in the later stages; this fast-later-stage feature could be suppressed by going to a synthesis with a 4�6Cd-to-1Se mole ratio: the nanocrystals between 0.5�60 min growth time exhibit very much similar optical properties, with less than 19 nm redshift of bandgap absorption and emission occurring. Thus, the synthetic route developed here, with a rational 4�6Cd-to-1Se molar ratio, enables us to produce high-quality CdSe nanocrystals on a large-scale with a high degree of synthetic reproducibility. The insights gained facilitate a deeper understanding of the concept of what constitutes high-quality nano-crystals: high PL efficiency resulting from a low growth rate, which can be thoroughly and readily investigated by the red-shift rate of the band-gap peak positions; in addition, the insights gained help us to define a proper synthetic approach for large-scale production with high-quality product.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences; NRC Institute for Biological Sciences
Peer reviewedNo
NPARC number12327193
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Record identifier60601f2c-1e30-4b25-95d9-72ca2f8534cb
Record created2009-09-10
Record modified2016-05-09
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