Yb, Nd, Er-doped upconversion nanoparticles: 980 nm versus 808 nm excitation. Issue 28 (9th July 2019)

• Record Type: Journal Article
• Authors: Wiesholler, Lisa M.; Frenzel, Florian; Grauel, Bettina; Würth, Christian; Resch-Genger, Ute; Hirsch, Thomas
• Is Part Of: Nanoscale. Volume 11:Issue 28(2019)
• Page Start: 13440
• Page End: 13449
• Publication Date: 2019-07-09
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c9nr03127h
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : A set of similarly sized (Yb 3+, Nd 3+, Er 3+ )-doped upconversion nanoparticles of different architecture were spectroscopically examined in water at broadly varied excitation power at 980 nm & 808 nm to study the sensitizer dependent penetration-depth. Abstract : Yb, Nd, Er-doped upconversion nanoparticles (UCNPs) have attracted considerable interest as luminescent reporters for bioimaging, sensing, energy conversion/shaping, and anticounterfeiting due to their capability to convert multiple near-infrared (NIR) photons into shorter wavelength ultraviolet, visible or NIR luminescence by successive absorption of two or more NIR photons. This enables optical measurements in complex media with very little background and high penetration depths for bioimaging. The use of Nd 3+ as substitute for the commonly employed sensitizer Yb 3+ or in combination with Yb 3+ shifts the excitation wavelength from about 980 nm, where the absorption of water can weaken upconversion luminescence, to about 800 nm, and laser-induced local overheating effects in cells, tissue, and live animal studies can be minimized. To systematically investigate the potential of Nd 3+ doping, we assessed the performance of a set of similarly sized Yb 3+, Nd 3+, Er 3+ -doped core- and core–shell UCNPs of different particle architecture in water at broadly varied excitation power densities ( P ) with steady state and time-resolved fluorometry for excitation at 980 nm and 808 nm. As a measure for UCNPs performance, the P -dependent upconversion quantum yield ( Φ UC ) and its saturation behavior were used as well as particle brightness ( B UC ). Based upon spectroscopic measurements at both excitation wavelengths in water and in a lipid phantom and B UC -based calculations of signal size at different penetration depths, conditions under which excitation at 808 nm is advantageous are derived and parameters for the further optimization of triple-doped UCNPs are given.