Size- and distance-dependent excitation energy transfer in fluorophore conjugated block copolymer – gold nanoparticle systems

Abstract

In the present work, we have demonstrated size- and distance-dependent excitation energy transfer (EET) phenomenon from polymer-bound fluorophores to gold nanoparticles (GNPs) conjugated to the same polymer. Anthracene labeled two block copolymers of controlled block length were synthesized by reversible-addition fragmentation chain transfer (RAFT) polymerization technique using two-arm dithioester chain transfer agent. The block copolymers were grafted onto the gold nanoparticle (GNP) surfaces by taking advantage of the high affinity of the dithioester end-groups located at the two ends of the polymer chains for the gold surface. GNPs of two different sizes, 20 nm and 55 nm, were used for the present study. The bare and polymer-bound GNPs were characterized by UV–vis spectroscopy, transmission electron microscopy and dynamic light scattering measurements. The EET process was monitored through steady-state and time-resolved fluorescence spectroscopic study. Thus we have successfully synthesized fluorophore labeled well-defined triblock copolymers with tailored architectures and subsequently anchored them with GNPs of different sized that enabled us to control the energy transfer process between GNPs and fluorescent polymer.