Variation of Metal Enhanced Fluorescence of Ag Nanoparticles Patterned by E-Beam Lithography with Size and Spacing

We report on metal-enhanced fluorescence measured on a silicon surface with silver nanoparticles patterned with electron beam lithography. We employ a combinatorial approach, depositing silver particles ranging in diameter from 50 nm to 130 nm, spaced at distances ranging from 150 nm to 390 nm onto the substrate, followed by a protein spacer-layer and fluorescein as fluorophore. The fluorescence enhancement was measured with an excitation source consisting of an Ar ion laser at 488 nm emission. This approach allows an easy and direct comparison of the enhancement to the particle size and spacing, with all other variables held constant. Our results show a variation of fluorescence enhancement with varying nanoparticle size and spacing which we relate to resonant plasmon coupling.