title: Electrostatic and covalent interactions in CdTe nanocrystalline assemblies.
abstract: This paper focuses on the interactions between cysteamine-stabilized CdTe nanocrystals [CdTe(CA) NCs] and thioglycolic-acid-stabilized CdTe nanocrystals [CdTe(TGA) NCs]. These interactions were examined by the absorption, continuous, and time-resolved photoluminescence (PL) spectra of the electrostatically mixed and the covalently linked NCs assemblies comprised of the oppositely surface charged CdTe(CA) and CdTe(TGA) NCs and by a comparison with those of the corresponding pristine NCs. The CdTe(CA)-CdTe(TGA) coupling is dictated by the surfactant spacer, ranging between 0.93 and 1.14 nm and by electrostatic and covalent interactions, enabling a Förster resonance energy transfer (FRET) process among the NCs. The results revealed an excellent spectral overlap between the emission of the CdTe(TGA) NCs and the absorption of the CdTe(CA) NCs as well as a PL spectral red shift on the formation of electrostatic and covalent interactions. Furthermore, the measurements showed a lifetime ranging between 1.2 and 3 ns for the electrostatically mixed and the covalently linked assemblies, shorter than those of the pristine CdTe(CA) NCs and CdTe(TGA) NCs, both of which measured as approximately 5.5 ns. When CdTe(TGA) NCs performed as the most efficient donors, FRET rates of 10(10)-10(11) s(-1) were calculated for the electrostatically mixed NCs or covalently linked NCs.
authors.affiliation: Department of Chemistry and Solid State Institute and the Russell Berrie Nanotechnology Institute, Technion, Haifa 32000, Israel. rutho@tx.technion.ac.il
authors.forename: Ruth
authors.initials: R
authors.lastname: Osovsky
authors.forename: Alexey
authors.initials: A
authors.lastname: Shavel
authors.forename: Nikolai
authors.initials: N
authors.lastname: Gaponik
authors.forename: Lilac
authors.initials: L
authors.lastname: Amirav
authors.forename: Alexander
authors.initials: A
authors.lastname: Eychmüller
authors.forename: Horst
authors.initials: H
authors.lastname: Weller
authors.forename: Efrat
authors.initials: E
authors.lastname: Lifshitz
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D003543:Cysteamine; D004355:Drug Stability; D031541:Fluorescence Resonance Energy Transfer; D036103:Nanotechnology / Q000379:methods*; D055672:Static Electricity; D013691:Tellurium / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002104:Cadmium; D003543:Cysteamine; D013691:Tellurium