title: Ligand induced circular dichroism and circularly polarized luminescence in CdSe quantum dots.
abstract: Chiral thiol capping ligands L- and D-cysteines induced modular chiroptical properties in achiral cadmium selenide quantum dots (CdSe QDs). Cys-CdSe prepared from achiral oleic acid capped CdSe by postsynthetic ligand exchange displayed size-dependent electronic circular dichroism (CD) and circularly polarized luminescence (CPL). Opposite CPL signals were measured for the CdSe QDs capped with D- and L-cysteine. The CD profile and CD anisotropy varied with size of CdSe nanocrystals with largest anisotropy observed for CdSe nanoparticles of 4.4 nm. Magic angle spinning solid state NMR (MAS ssNMR) experiments suggested bidentate interaction between cysteine and the surface of CdSe. Time Dependent Density Functional Theory (TDDFT) calculations verified that attachment of L- and D-cysteine to the surface of model (CdSe)13 nanoclusters induces measurable opposite CD signals for the exitonic band of the nanocluster. The origin of the induced chirality is consistent with the hybridization of highest occupied CdSe molecular orbitals with those of the chiral ligand.
authors.affiliation: Department of Chemistry, University of Wyoming , 1000 East University Avenue, Laramie, Wyoming 82071, United States .
authors.forename: Urice
authors.initials: U
authors.lastname: Tohgha
authors.forename: Kirandeep K
authors.initials: KK
authors.lastname: Deol
authors.forename: Ashlin G
authors.initials: AG
authors.lastname: Porter
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Bartko
authors.forename: Jung Kyu
authors.initials: JK
authors.lastname: Choi
authors.forename: Brian M
authors.initials: BM
authors.lastname: Leonard
authors.forename: Krisztina
authors.initials: K
authors.lastname: Varga
authors.forename: Jan
authors.initials: J
authors.lastname: Kubelka
authors.forename: Gilles
authors.initials: G
authors.lastname: Muller
authors.forename: Milan
authors.initials: M
authors.lastname: Balaz
mesh_terms: D016880:Anisotropy; D019187:Cadmium Compounds / Q000737:chemistry*; D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry; D008024:Ligands; D049449:Luminescence; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology; D019301:Oleic Acid / Q000737:chemistry; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014466:Ultraviolet Rays
chemical_list: D019187:Cadmium Compounds; D008024:Ligands; D018036:Selenium Compounds; D019301:Oleic Acid; C058667:cadmium selenide; D003545:Cysteine