Enhanced UV Upconversion Emission Using Plasmonic Nanocavities

Abstract

Upconversion of near infrared (NIR) into ultraviolet (UV) radiation could lead to a number of applications in bio-imaging, diagnostics and drug delivery. However, for bare nanoparticles, the conversion efficiency is extremely low. In this work, we experimentally demonstrate strongly enhanced upconversion emission from an ensemble of β-NaYF 4 :Gd 3+ /Yb 3+ /Tm 3+ @NaLuF 4 core-shell nanoparticles trapped in judiciously designed plasmonic nanocavities. In doing so, different metal platforms and nanostructures are systematically investigated. Our results indicate that using a cross-shape silver nanocavity, a record high enhancement of 170-fold can be obtained in the UV band centered at a wavelength of 345 nm. The observed upconversion efficiency improvement may be attributed to the increased absorption at NIR, the tailored photonic local density of states, and the light out-coupling characteristics of the cavity. References and links1. F. Auzel, "Upconversion and anti-Stokes processes with f and d ions in solids," Chem. Rev. 104(1), 139-174 (2004). 2. X. Li, F. Zhang, and D. Zhao, "Highly efficient lanthanide upconverting nanomaterials: progresses and challenges," Nano Today 8(6), 643-676 (2013). 3. N. Bloembergen, "Solid state infrared quantum counters," Phys. Rev. Lett. 2(3), 84-85 (1959) . 36. E. M. Purcell, "Spontaneous emission probabilities at radio frequencies," Phys. Rev. 69, 681 (1946). 37.

Controlling Surface Plasmon Resonance of Metal Nanocap for Upconversion Enhancement

“…Substantial efforts, including the development of new host media and optimization of assisting dopants, have been devoted to improve the upconversion efficiency. 9,10 Another promising approach for the improvement of upconversion efficiency is utilizing surface plasmon resonance of metal nanostructures. 5,9,11−18 A variety of composite nanoparticles (NPs) consisting of upconversion materials and metal nanostructures have been developed 7,14,19−22 and the enhancement of the upconversion has been demonstrated.…”