Plasmonic‐Enhanced NIR‐II Downconversion Fluorescence beyond 1500 nm from Core–Shell–Shell Lanthanide Nanoparticles
Jiamin Xu, Ming Fu, Chengyu Ji, Anthony Centeno, Dong Kuk Kim, Koen Evers, Sandrine Heutz, Rupert F. Oulton, Mary P. Ryan, Fang Xie
Abstract
Abstract This paper reports on the light amplification of NaGdF 4 :Yb,Er,Ce@NaGdF 4 :Yb,Nd@NaGdF 4 core–shell–shell downconversion nanoparticles (CSS‐DCNPs) in the near‐infrared second biological window (NIR‐II: 1000–1700 nm) by plasmonic nanostructures. Through a precisely controlled plasmonic metallic nanostructure, fluorescence from Yb 3+ induced 1000 nm emission, Nd 3+ induced 1060 nm emission, and Er 3+ induced 1527 nm emission are enhanced 1.6‐fold, 1.7‐fold, and 2.2‐fold, respectively, under an 808 nm laser excitation for the CSS‐DCNPs coupled with a gold hole‐cap nanoarray (Au‐HCNA), while the Er 3+ induced 1527 nm emission under a 980 nm laser excitation is enhanced up to 6‐fold. To gain insight into the enhancement mechanism, the plasmonic modulation of Er 3+ induced NIR‐II emission at 1550 nm under 980 nm excitation is studied by FDTD simulation and lifetime measurements, showing the observed fluorescence enhancement can be attributed to a combination of enhanced excitation and an increased radiative decay rate.