title: Water soluble quantum dot nanoclusters: energy migration in artifical materials.
abstract: Energy migration in self-assembled, water soluble, quantum dot (QD) nanoclusters is reported. These spherical nanoclusters are composed of CdSe QDs bound together by pepsin, a digestive enzyme found in mammals. A structural model for the clusters is suggested, based on scanning transmission electron microscopy, as well as dynamic light scattering and small angle X-ray scattering. Cluster sizes range from 100 to 400 nm in diameter and show a close-packed interior structure. Optical characterization of the absorption and emission spectra of the clusters is reported, finding photoluminescence quantum yields of up to approximately 60% in water for clusters made from core-shell CdSe-ZnS QDs. Clusters prepared from two different size populations of CdSe QD samples (3 and 4 nm in diameter) demonstrate energy migration and trapping. Resonance energy transfer (RET), from small to large dots within the QD-pepsin cluster, is observed by monitoring the quenching of the small donor dot fluorescence along with enhancement of the large acceptor dot fluorescence.
authors.affiliation: Lash-Miller Chemical Laboratories and the Institute for Optical Sciences, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
authors.forename: Megan H J
authors.initials: MH
authors.lastname: Oh
authors.forename: Darcy J
authors.initials: DJ
authors.lastname: Gentleman
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Scholes
mesh_terms: D000042:Absorption; D002104:Cadmium / Q000737:chemistry; D002627:Chemistry, Physical / Q000379:methods*; D004735:Energy Transfer; D008027:Light; D008422:Materials Testing; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D010434:Pepsin A / Q000737:chemistry; D045663:Quantum Dots; D012542:Scattering, Radiation; D012643:Selenium / Q000737:chemistry; D013053:Spectrophotometry
chemical_list: D002104:Cadmium; D010434:Pepsin A; D012643:Selenium