title: Linear dipole behavior in single CdSe-oligo(phenylene vinylene) nanostructures.
abstract: We report on linearly polarized absorption and emission from individual (4.3 nm) CdSe quantum dots whose surfaces are coordinated with monodisperse oligo-phenylene vinylene ligands. Shown previously to suppress quantum dot blinking, we demonstrate here that the electronic interaction of photoexcited ligands with the quantum dot core is manifested as a strong polarization anisotropy in absorption (M = 0.5), as well as distinct linear dipole emission patterns from the quantum dot core. Further, there is a correlation between the quantum dot emission moment and polarization orientation corresponding to the absorption maxima that is manifested as fluctuations in emission moment orientation in the X-Y plane. The observed polarization effects can be switched off by tuning the excitation away from the ligand absorption band. We propose a mechanism based on exciton dissociation from the photoexcited ligand, followed by the pinning of electrons at the quantum dot surface. The resulting Stark interaction is sufficiently strong to break the 2D degeneracy of the emission moment within the dot, and may therefore account for the linear dipole emission character.
authors.affiliation: George R. Richason Jr. Chemistry Laboratory, Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
authors.forename: K T
authors.initials: KT
authors.lastname: Early
authors.forename: K D
authors.initials: KD
authors.lastname: McCarthy
authors.forename: M Y
authors.initials: MY
authors.lastname: Odoi
authors.forename: P K
authors.initials: PK
authors.lastname: Sudeep
authors.forename: T
authors.initials: T
authors.lastname: Emrick
authors.forename: M D
authors.initials: MD
authors.lastname: Barnes
mesh_terms: D000042:Absorption; D019187:Cadmium Compounds / Q000737:chemistry*; D005453:Fluorescence; D053761:Nanocomposites / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry*; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D019187:Cadmium Compounds; D011145:Polyvinyls; D018036:Selenium Compounds; C530822:oligo(p-phenylene vinylene); C058667:cadmium selenide