UV Fluorescence Lifetime Modification by Aluminum Nanoapertures

We report excited-state lifetime modification of diffusing molecules by Al nanoapertures in the UV. Lifetime reductions of similar to 3.5X have been observed for the high quantum yield laser dye p-terphenyl in a 60 nm diameter aperture. The lifetime reduction is smaller for the low quantum yield molecule tryptophan, for which a maximum reduction of similar to 1.7 is observed. Lifetime reduction as a function of aperture size and native quantum yield is accurately predicted by simulation. Simulation further predicts greater net fluorescence enhancement for tryptophan compared to p-terphenyl, which is consistent with the expectation that low quantum yield emitters experience greater enhancement in the effective quantum yield.