UV fluorescence enhancement by Al and Mg nanoapertures

Aluminum and magnesium have a strong plasmonic response in the ultraviolet part of the spectrum. Due to the differences in their dielectric responses, however, there are qualitative differences in the fluorescence enhancement factors for Al and Mg nanoapertures. In order to make our results applicable to experimental studies, we further investigate fluorescence enhancement in these nanoapertures using UV emitters that excite near 270 nm and emit near 340 nm with both high and low quantum yields (QY). Our results suggest that Al nanoapertures may perform better for molecules with low QY, while Mg may perform better for molecules with high QY. We further consider the effects of bulk and surface oxidation of the two metals. In order to improve fluorescence enhancement, avoiding bulk oxidation during film deposition is important, although bulk oxidation could be used as an optimization parameter for some enhancement mechanisms. (paper)