Plasmonic nanoparticles can strongly interact with adjacent fluorophores resulting in plasmon-enhanced fluorescence or fluorescence quenching. Dipolar coupling is dependent upon the composition of the nanoparticle, distance between the fluorophore and the plasmonic surface, the transition dipole orientation and the fluorophore's absorbance/emission wavelengths relative to the surface plasmon band of the nanoparticles.In this work, we examine the distance and plasmon wavelength dependent fluorescence of IRDye 800CW DBCO bound to gold nanorods. Nanorods with plasmon bands ranging from 530 � 850 nm are synthesized and coated with mesoporous silica shells 11 � 26 nm thick. IRDye is covalently attached to the silica surface via copper-free click chemistry. Using time-resolved techniques, a strong reduction in fluorescence lifetime is observed with decreasing silica shell thickness and when the plasmon band is closer to IRDye absorption/emission, with no loss in emission intensity. Steady-state measurements also demonstrate wavelength and distance dependent emission. Maximum fluorescence intensity with a 10 fold enhancement is observed with 17 nm silica shells when the gold nanorod plasmon band is resonant with IRDye absorption.In addition, control experiments are carried out to confirm that the observed changes in fluorescence are due to plasmonic interactions, not simply attachment to a silica surface. There is no change in fluorescence lifetime or steady-state intensity when IRDye is bound to mesoporous silica nanoparticles. In addition, IRDye loading is limited to maintain a distance between dye molecules on the surface to more than 9 nm, well above the F�rster radius. This assures minimal dye-dye interactions on the surface of the nanoparticles.

Distance and plasmon wavelength dependent fluorescence of molecules bound to silica-coated gold nanorods: A study of plasmon-induced luminescence enhancement

248th National Meeting (2014)

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