Surface plasmon enhanced fluorescence of cationic conjugated polymer on periodic nanoarrays

The fluorescence from conjugated polymer assembled onto lithographically fabricated gold nanoarrays using genetically engineered peptides as molecular linkers is studied. A 16-fold increase in the photoluminescence of the conjugated polymer is observed when assembled on the optimized nanostructures due to surface plasmon enhanced fluorescence. This is achieved using a water-soluble cationic conjugated polymer, poly[(9,9-bis(6′-((N,N,N- trimethylammonium)hexyl)-2,7-fluorene)-co-4,7-di-2-thienyl-2,1, 3-benzothiadiazole] dibromide (PFDBT-N⁺), systematically tuning the vertical distance of PFDBT-N⁺ from the gold nanopillar surface using solid-specific peptide linkers and horizontally optimizing the localized surface plasmon resonance by varying the geometric arrangements of the patterned metal nanoarrays. The diameter and tip-to-tip spacing of the nanopillars along with vertically tuning the distance of PFDBT-N⁺ from the nanopillar affected the observed fluorescence enhancements. The collective optical properties of conjugated polymers combined with the photonic properties of nanoparticles provide a new means in the development of metal enhanced hybrid nanomaterials for biotechnology. © 2010 American Chemical Society.