Plasmonic-Enhanced NIR-II Downconversion Fluorescence beyond 1500 nm from Core-Shell-Shell Lanthanide Nanoparticles

This paper reports on the light amplification of NaGdF4:Yb,Er,Ce@NaGdF4:Yb,Nd@NaGdF4 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 Yb3+ induced 1000 nm emission, Nd3+ induced 1060 nm emission, and Er3+ 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 Er3+ 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 Er3+ 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.

Automated summary

This study reports on the light amplification of NaGdF4:Yb,Er,Ce@NaGdF4:Yb,Nd@NaGdF4 core-shell-shell downconversion nanoparticles (CSS-DCNPs) in the near-infrared second biological window (NIR-II: 1000-1700 nm) using plasmonic nanostructures. The fluorescence emissions at 1000 nm, 1060 nm, and 1527 nm induced by Yb3+, Nd3+, and Er3+, respectively, are enhanced through a precisely controlled plasmonic metallic nanostructure. Further enhancement of the 1527 nm emission is observed under a 980 nm laser excitation. The observed fluorescence enhancement is attributed to enhanced excitation and an increased radiative decay rate.