Absolute upconversion quantum yields of blue-emitting LiYF₄:Yb³⁺,Tm³⁺ upconverting nanoparticles

Abstract

The upconversion quantum yield (ΦUC) is an essential parameter for the characterization of the optical performance of lanthanoid-doped upconverting nanoparticles (UCNPs). Despite its nonlinear dependence on excitation power density (Pexc), it is typically reported only as a single number. Here, we present the first measurement of absolute upconversion quantum yields of the individual emission bands of blue light-emitting LiYF4:Yb3+,Tm3+ UCNPs in toluene. Reporting the quantum yields for the individual emission bands is required for assessing the usability of UCNPs in various applications that require upconverted light of different wavelengths, such as bioimaging, photocatalysis and phototherapy. Here, the reliability of the ΦUC measurements is demonstrated by studying the same batch of UCNPs in three different research groups. The results show that whereas the total upconversion quantum yield of these UCNPs is quite high-typically 0.02 at a power density of 5 W cm-2-most of the upconverted photon flux is emitted in the 794 nm upconversion band, while the blue emission band at 480 nm is very weak, with a much lower quantum yield of ∼6 × 10-5 at 5 W cm-2. Overall, although the total upconversion quantum yield of LiYF4:Yb3+,Tm3+ UCNPs seems satisfying, notably for NIR bioimaging, blue-light demanding phototherapy applications will require better-performing UCNPs with higher blue light upconversion quantum yields.

NIR-Light-Driven Generation of Reactive Oxygen Species Using Ru(II)-Decorated Lipid-Encapsulated Upconverting Nanoparticles

“…Using an absolute method described by us recently, 66 the upconversion quantum yields (Φ UC ) of the individual emission bands of these UCNPs in toluene dispersion could be determined (Figures 2C and S4). At the maximum excitation power density used here (50 W cm –2 ), the total upconversion quantum yield (Φ UC,total ) was found to be 0.044 ± 0.006.…”

LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals

“…Lanthanide-doped LiYF4 can also be prepared in the form of nanocrystals with very narrow size distribution . This is usually done in high boiling oleic acid-based solvent mixtures, similar to the synthesis of NaYF4 upconversion nanocrystals [62][63][64][65][66]. Since the particles have a small size and display a relatively strong luminescence, they have been proposed for a variety of biomedical and bioimaging applications [79,80,83,87], as well as for transparent displays [70,74] and chemosensing [86].…”

“…Core particle synthesisHOA-based synthesis procedures for nanocrystalline LiYF4 are usually based on the thermal decomposition of trifluoro acetates[63,64,66,67,[78][79][80][81][82][83][84][85][86][87][88][89] or on the reaction of yttrium oleate with either ammonium fluoride and lithium oleate[77] or ammonium fluoride and lithium hydroxide[62,65,[68][69][70][71][72][73][74][75][76]. Here, we prepared the LiYF4 nanoparticles at temperatures above 200 °C via the reaction of ammonium fluoride with rare earth oleates and lithium oleate dissolved in oleic acid/octadecene[62,65,[68][69][70][71][72][73][74][75][76][77].…”

Люминесцентные Наноматериалы, Допированные Редкоземельными Ионами, И Перспективы Их Биомедицинского Применения (Обзор)

“…Для повышения эффективности ап-конверсионной люминесценции наряду с ионами Er 3+ и Tm 3+ в качестве сенсибилизатора часто используют ионы Yb 3+ [71][72][73]. Зеленые и красные полосы ап-конверсионной люминесценции в основном связаны с электронными переходами 3+ .…”