A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands

Controlled Suzuki-Miyaura coupling polymerization of 7-bromo-9,9-dioctyl-fluoren-2-yl-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane initiated by bromo(4-tert-butoxycarbonylamino-phenyl)(tri-tert-butylphosphine)palladium (1) or bromo(4-diethoxyphosphoryl-phenyl)(tri-tert-butylphosphine)palladium (2) yields functionalized polyfluorenes (M-n = 4 x 10(3) g mol(-1), M-w/M-n < 1.2) with a single amine or phosphonic acid, respectively, end-group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution sigma < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino-functionalized polyfluorene ligands. Single particle micro-photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot.