Surface plasmon coupled fluorescence in the ultraviolet and visible spectral regions using zinc thin films

The use of zinc thin films deposited onto glass supports for surface plasmon coupled fluorescence (SPCF) over a broad 200 nm wavelength range is demonstrated. Fresnel calculations performed in the ultraviolet and visible spectral range are predicted to generate surface plasmon modes in 30 nm zinc thin films. In this spectral range, the extent of coupling of light to zinc thin films was shown to be significant as compared to similar aluminum, gold, and silver thin films. The experimental demonstration of SPCF using 30 nm zinc thin films in the ultraviolet and visible spectral regions was undertaken using three different fluorophores 2-AP, POPOP, and FITC, respectively. Surface plasmon coupled fluorescence from zinc thin films was p-polarized and highly directional with lambda max conferred at an angle of 58, 68, and 60 degrees for FITC, POPOP, and 2-AP, respectively. s-Polarized emission from zinc thin films was negligible for all fluorophores except for a sample spin coated from a 10% PVA solution, which resulted in significant s-polarized emission due to the generation of waveguide modes. The experimental results are consistent with reflectivity curves that are theoretically predicted using Fresnel calculations. Given the growing use and utility of plasmon-enhanced fluorescence in the analytical and biological sciences, our findings will serve as a useful tool for workers in the ultraviolet and visible spectral regions.