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Nano Research 2019, 12(8): 1871-1879 https://doi.org/10.1007/s12274-019-2450-4
Research Article | Issue | Published: 20 June 2019

Explaining the influence of dopant concentration and excitation power density on the luminescence and brightness of β-NaYF4: Yb3+, Er3+ nanoparticles: Measurements and simulations

Show Author's Information Martin Kaiser1,  Christian Würth1,  Marco Kraft1,  Tero Soukka2,  Ute Resch-Genger1( )
Division Biophotonics, Federal Institute for Materials Research and Testing (BAM),Richard-Willstaetter-Str. 11,D-12489,Berlin, Germany;
Department of Biotechnology,University of Turku, Kiinamyllynkatu 10,Turku,FI-20520,Finland;
Keywords:
nanoparticles, upconversion, quantum yield, color tuning, dopant concentration, rate equation model
Topics:
LuminanceLuminescenceNanoparticlesQuantum yieldSemiconductor doping
Cite this article:
Kaiser M, Würth C, Kraft M, et al. Explaining the influence of dopant concentration and excitation power density on the luminescence and brightness of β-NaYF4: Yb3+, Er3+ nanoparticles: Measurements and simulations. Nano Research, 2019, 12(8): 1871-1879. https://doi.org/10.1007/s12274-019-2450-4
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Abstract Full text Electronic supplementary material About this article

We assessed the influence of Yb3+ and Er3+ dopant concentration on the relative spectral distribution, quantum yield (ƵUC), and decay kinetics of the upconversion luminescence (UCL) and particle brightness (BUC) for similarly sized (33 nm) oleate-capped β-NaYF4: Yb3+, Er3+ upconversion (UC) nanoparticles (UCNPs) in toluene at broadly varied excitation power densities (P). This included an Yb3+ series where the Yb3+ concentration was varied between 11%Ƀ21% for a constant Er3+ concentration of 3%, and an Er3+ series, where the Er3+ concentration was varied between 1%Ƀ4% for a constant Yb3+ concentration of 14%. The results were fitted with a coupled rate equation model utilizing the UCL data and decay kinetics of the green and red Er3+ emission and the Yb3+ luminescence at 980 nm. An increasing Yb3+ concentration favors a pronounced triphotonic population of 4F9/2 at high P by an enhanced back energy transfer (BET) from the 4G11/2 level. Simultaneously, the Yb3+-controlled UCNPs absorption cross section overcompensates for the reduction in ƵUC with increasing Yb3+ concentration at high P, resulting in an increase in BUC. Additionally, our results show that an increase in Yb3+ and a decrease in Er3+ concentration enhance the color tuning range by P. These findings will pave the road to a deeper understanding of the energy transfer processes and their contribution to efficient UCL, as well as still debated trends in green-to-red intensity ratios of UCNPs at different P.


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About this article

Explaining the influence of dopant concentration and excitation power density on the luminescence and brightness of β-NaYF4: Yb3+, Er3+ nanoparticles: Measurements and simulations

Show Author's information Martin Kaiser1, Christian Würth1, Marco Kraft1, Tero Soukka2, Ute Resch-Genger1( )
Division Biophotonics, Federal Institute for Materials Research and Testing (BAM),Richard-Willstaetter-Str. 11,D-12489,Berlin, Germany;
Department of Biotechnology,University of Turku, Kiinamyllynkatu 10,Turku,FI-20520,Finland;

Abstract

We assessed the influence of Yb3+ and Er3+ dopant concentration on the relative spectral distribution, quantum yield (ƵUC), and decay kinetics of the upconversion luminescence (UCL) and particle brightness (BUC) for similarly sized (33 nm) oleate-capped β-NaYF4: Yb3+, Er3+ upconversion (UC) nanoparticles (UCNPs) in toluene at broadly varied excitation power densities (P). This included an Yb3+ series where the Yb3+ concentration was varied between 11%Ƀ21% for a constant Er3+ concentration of 3%, and an Er3+ series, where the Er3+ concentration was varied between 1%Ƀ4% for a constant Yb3+ concentration of 14%. The results were fitted with a coupled rate equation model utilizing the UCL data and decay kinetics of the green and red Er3+ emission and the Yb3+ luminescence at 980 nm. An increasing Yb3+ concentration favors a pronounced triphotonic population of 4F9/2 at high P by an enhanced back energy transfer (BET) from the 4G11/2 level. Simultaneously, the Yb3+-controlled UCNPs absorption cross section overcompensates for the reduction in ƵUC with increasing Yb3+ concentration at high P, resulting in an increase in BUC. Additionally, our results show that an increase in Yb3+ and a decrease in Er3+ concentration enhance the color tuning range by P. These findings will pave the road to a deeper understanding of the energy transfer processes and their contribution to efficient UCL, as well as still debated trends in green-to-red intensity ratios of UCNPs at different P.

Keywords: nanoparticles, upconversion, quantum yield, color tuning, dopant concentration, rate equation model

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Publication history
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Acknowledgements

Publication history

Received: 17 February 2019
Revised: 29 May 2019
Accepted: 30 May 2019
Published: 20 June 2019
Issue date: August 2019

Copyright

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Acknowledgements

Acknowledgements

Synthesis of the UCNPs by Emilia Palo and performance of the ICP-OES measurements by MSc. Melissa Monks is gratefully acknowledged. URG acknowledges financial support by research grants RE 1203/18-1 (German research council; DFG), RE 1203/20-1 (project NANOHYPE; DFG and M-Eranet) and TS from Tekes, the Finnish Funding Agency for Innovation.

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