Beyond superquenching: Hyper-efficient energy transfer from conjugated polymers to gold nanoparticles

doi:10.1073/pnas.1132025100

Beyond superquenching: Hyper-efficient energy transfer from conjugated polymers to gold nanoparticles

^*Institute for Polymers and Organic Solids, Departments of ^†Chemistry and Biochemistry, ^‡Materials, ^§Interdepartmental Biomolecular Science and Engineering Program, and ^¶Department of Physics, University of California, Santa Barbara, CA 93106;

Contributed by Alan J. Heeger, April 7, 2003

Abstract

Gold nanoparticles quench the fluorescence of cationic polyfluorene with Stern–Volmer constants (K _SV) approaching 10¹¹ M^— ¹, several orders of magnitude larger than any previously reported conjugated polymer–quencher pair and 9–10 orders of magnitude larger than small molecule dye–quencher pairs. The dependence of K_SV on ionic strength, charge and conjugation length of the polymer, and the dimensions (and thus optical properties) of the nanoparticles suggests that three factors account for this extraordinary efficiency: (i) amplification of the quenching via rapid internal energy or electron transfer, (ii) electrostatic interactions between the cationic polymer and anionic nanoparticles, and (iii) the ability of gold nanoparticles to quench via efficient energy transfer. As a result of this extraordinarily high K_SV, quenching can be observed even at subpicomolar concentrations of nanoparticles, suggesting that the combination of conjugated polymers with these nanomaterials can potentially lead to improved sensitivity in optical biosensors.

Footnotes

↵ ∥ To whom correspondence should be addressed. E-mail: ajh{at}physics.ucsb.edu.
Abbreviations: PF, poly(9,9′-bis(6-N,N,N-trimethylammonium)-hexyl)-fluorene phenylene; PL, photoluminescence; K _SV, Stern–Volmer quenching constant; (PRU/Q)₅₀, polymer repeat units per quencher at 50% quenching; 2-OF, 2-oligofluorene; OPV, oligophenylene vinylene.