Multiband emission from single β-NaYF_(4)(Yb,Er) nanoparticles at high excitation power densities and comparison to ensemble studies  

作　　者：Florian Frenzel Christian Würth Oleksii Dukhno Frédéric Przybilla Lisa MWiesholler Verena Muhr Thomas Hirsch Yves Mély Ute Resch-Genger 

机构地区：[1]Federal Institute for Materials Research and Testing(BAM),Division 1.2 Biophotonics,Richard-Willstaetter-Str.11,12489,Berlin,Germany [2]Laboratory of Biomaging and Pathologies,UMR 7021 CNRS,University of Strasbourg,67000,Strasbourg,France [3]Institute of Analytical Chemistry,Chemo-and Biosensors,University of Regensburg,93040,Regensburg,Germany [4]Institut für Physik and IRIS Adlershof,Humboldt-Universität zu Berlin,Newtonstraße 15,12489,Berlin,Germany

出　　处：《Nano Research》2021年第11期4107-4115,共9页纳米研究（英文版）

基　　金：The authors thank the European Upconversion Network(EUN)for financial support of a research exchange program(COST-CM1403);U.R.-G.,F.F.and C.W.acknowledge financial support by research grants RE 1203/20-1(project NANOHYPE,DFG and M-Eranet).Y.M.is grateful to the Institut Universitaire de France(IUF)for support and providing additional time to be dedicated to research.

摘　　要：Ensemble and single particle studies of the excitation power density (P)-dependent upconversion luminescence (UCL) of core and core-shell β-NaYF_(4):Yb,Er upconversion nanoparticles (UCNPs) doped with 20% Yb^(3+) and 1% or 3% Er^(^(3+)) performed over a P regime of 6 orders of magnitude reveal an increasing contribution of the emission from high energy Er^(3+) levels at P > 1 kW/cm^(2). This changes the overall emission color from initially green over yellow to white. While initially the green and with increasing P the red emission dominate in ensemble measurements at P < 1 kW/cm^(2), the increasing population of higher Er^(^(3+)) energy levels by multiphotonic processes at higher P in single particle studies results in a multitude of emission bands in the ultraviolet/visible/near infrared (UV/vis/NIR) accompanied by a decreased contribution of the red luminescence. Based upon a thorough analysis of the P-dependence of UCL, the emission bands activated at high P were grouped and assigned to 2–3, 3–4, and 4 photonic processes involving energy transfer (ET), excited-state absorption (ESA), cross-relaxation (CR), back energy transfer (BET), and non-radiative relaxation processes (nRP). This underlines the P-tunability of UCNP brightness and color and highlights the potential of P-dependent measurements for mechanistic studies required to manifest the population pathways of the different Er^(3+) levels.

关 键 词：upconversion luminescence single nanoparticle study high power excitation emission color luminescence decay kinetics 

分 类 号：O57[理学—粒子物理与原子核物理]