Engineering Bright and Mechanosensitive Alkaline-Earth Rare-Earth Upconverting Nanoparticles

Claire A McLellan; Chris Siefe; Jason R Casar; Chunte Sam Peng; Stefan Fischer; Alice Lay; Abhinav Parakh; Feng Ke; X Wendy Gu; Wendy Mao; Steven Chu; Miriam B Goodman; Jennifer A Dionne

doi:10.1021/acs.jpclett.1c03841

Engineering Bright and Mechanosensitive Alkaline-Earth Rare-Earth Upconverting Nanoparticles

J Phys Chem Lett. 2022 Feb 17;13(6):1547-1553. doi: 10.1021/acs.jpclett.1c03841. Epub 2022 Feb 8.

Authors

Claire A McLellan¹, Chris Siefe¹, Jason R Casar¹, Chunte Sam Peng^{2

3}, Stefan Fischer¹, Alice Lay⁴, Abhinav Parakh¹, Feng Ke⁵, X Wendy Gu⁶, Wendy Mao⁵, Steven Chu^{2

3}, Miriam B Goodman³, Jennifer A Dionne^{1

7}

Affiliations

¹ Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
² Department of Physics, Stanford University, Stanford, California 94305, United States.
³ Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, United States.
⁴ Department of Applied Physics, Stanford University, Stanford, California 94305, United States.
⁵ Department of Geological Sciences, Stanford University, Stanford, California 94305, United States.
⁶ Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States.
⁷ Department of Radiology, Stanford University, Stanford, California 94305, United States.

Abstract

Upconverting nanoparticles (UCNPs) are an emerging platform for mechanical force sensing at the nanometer scale. An outstanding challenge in realizing nanometer-scale mechano-sensitive UCNPs is maintaining a high mechanical force responsivity in conjunction with bright optical emission. This Letter reports mechano-sensing UCNPs based on the lanthanide dopants Yb³⁺ and Er³⁺, which exhibit a strong ratiometric change in emission spectra and bright emission under applied pressure. We synthesize and analyze the pressure response of five different types of nanoparticles, including cubic NaYF₄ host nanoparticles and alkaline-earth host materials CaLuF, SrLuF, SrYbF, and BaLuF, all with lengths of 15 nm or less. By combining optical spectroscopy in a diamond anvil cell with single-particle brightness, we determine the noise equivalent sensitivity (GPa/√Hz) of these particles. The SrYb_0.72Er_0.28F@SrLuF particles exhibit an optimum noise equivalent sensitivity of 0.26 ± 0.04 GPa/√Hz. These particles present the possibility of robust nanometer-scale mechano-sensing.

Abstract

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