Gold coated Cicada wings: A plasmon coupled anti-reflective micro-environment for fluorescence enhancement in silica coated upconversion nanoparticles

Akash Gupta^1*, Kung-Hsuan Lin², Surojit Chattopadhyay¹

¹Biophotonics, National Yang Ming University, Taipei, Taiwan
²Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Akash Gupta, email:gupta.akash00@gmail.com

Upconversion nanoparticles (UCNPs) are attractive bioimaging, and therapeutic materials as it is excited in the infrared (IR), however, limited by the low quantum yield. Here, a plasmonic effect of a gold coating, coupled with an anti-reflecting (AR) Cicada wing substrate, is demonstrated to enhance the fluorescence of the UCNPs. Silica (SiO2) coated Erbium doped green emitting core-shell UCNPs (NaYF4: Yb3+, Er3+@SiO2) show conventional metal enhanced fluorescence. The anti-reflection property of the Cicada wing (R~ 0.2 % @ 1000 nm) contributes >6 X enhancement as compared to flat (silicon) substrates (R~30% @ 1000 nm). Upon plasmon coupling, with an optimized sputtered Au coating, an unprecedented enhancement of >50 X for the 520, and 655 nm emission was obtained on the gold coated Cicada wings, vis-à-vis planar uncoated (silicon) substrates. The enhancement was also confirmed by direct fluorescence imaging of the photonic substrates used.

Keywords: Upconversion Nanoparticles, Cicada wing, Photonic substrate, Anti-reflection, Plasmonic Enhancement