Plasmonic enhancement of nanophosphor upconversion luminescence in Au nanohole arrays

Arrays of subwavelength holes (nanoholes) in Au films were computationally designed, fabricated, and used as templates to localize and enhance the luminescence of upconversion nanophosphors (UCNPs)--hexagonal phase NaYF4 doped with Yb(3+) and Er(3+). The dimensions of nanohole Au arrays were designed to accept only a single UCNP upon particle filling and with a periodicity to be resonant with the excitation wavelength of the upconversion. Frequency-dependent luminescence enhancements of up to 35-fold and a concomitant shortening of the UCNP luminescence rise time were observed, consistent with simulations of plasmonic enhancement of the UCNP absorption.