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Lu D, Cho SK, Ahn S, et al. Plasmon enhancement mechanism for the upconversion processes in NaYF4:Yb(3+),Er(3+) nanoparticles: Maxwell versus Förster. ACS Nano. 2014;8(8):7780-92doi: 10.1021/nn5011254.
Lu, D., Cho, S. K., Ahn, S., Brun, L., Summers, C. J., & Park, W. (2014). Plasmon enhancement mechanism for the upconversion processes in NaYF4:Yb(3+),Er(3+) nanoparticles: Maxwell versus Förster. ACS nano, 8(8), 7780-92. https://doi.org/10.1021/nn5011254
Lu, Dawei, et al. "Plasmon enhancement mechanism for the upconversion processes in NaYF4:Yb(3+),Er(3+) nanoparticles: Maxwell versus Förster." ACS nano vol. 8,8 (2014): 7780-92. doi: https://doi.org/10.1021/nn5011254
Lu D, Cho SK, Ahn S, Brun L, Summers CJ, Park W. Plasmon enhancement mechanism for the upconversion processes in NaYF4:Yb(3+),Er(3+) nanoparticles: Maxwell versus Förster. ACS Nano. 2014 Aug 26;8(8):7780-92. doi: 10.1021/nn5011254. Epub 2014 Jul 14. PMID: 25003209.
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ACS Nano. 2014 Aug 26;8(8):7780-92. doi: 10.1021/nn5011254. Epub 2014 Jul 14.

Plasmon enhancement mechanism for the upconversion processes in NaYF4:Yb(3+),Er(3+) nanoparticles: Maxwell versus Förster.

ACS nano

Dawei Lu, Suehyun K Cho, Sungmo Ahn, Loic Brun, Christopher J Summers, Wounjhang Park

Affiliations

  1. Department of Electrical, Computer & Energy Engineering and ‡Materials Science & Engineering Program, University of Colorado , Boulder, Colorado 80309, United States.

PMID: 25003209 DOI: 10.1021/nn5011254

Abstract

Rare-earth activated upconversion materials are receiving renewed attention for their potential applications in bioimaging and solar energy conversion. To enhance the upconversion efficiency, surface plasmon has been employed but the reported enhancements vary widely and the exact enhancement mechanisms are not clearly understood. In this study, we synthesized upconversion nanoparticles (UCNPs) coated with amphiphilic polymer which makes UCNPs water soluble and negatively charged. We then designed and fabricated a silver nanograting on which three monolayers of UCNPs were deposited by polyelectrolyte-mediated layer-by-layer deposition technique. The final structures exhibited surface plasmon resonance at the absorption wavelength of UCNP. The green and red photoluminescence intensity of UCNPs on nanograting was up to 16 and 39 times higher than the reference sample deposited on flat silver film, respectively. A thorough analysis of rate equations showed that the enhancement was due entirely to absorption enhancement in the strong excitation regime, while the enhancement of both absorption and Förster energy transfer contribute in the weak excitation regime. The Purcell factor was found to be small and unimportant because the fast nonradiative decay dominates the relaxation process. From the experimentally observed enhancements, we concluded 3.1× and 1.7× enhancements for absorption and Förster energy transfer, respectively. This study clearly shows the plasmon enhancement mechanism and its excitation power dependence. It provides the basis for comparison of the enhancements of various plasmonic UCNP systems in the literature. It also lays the foundation for rational design of optical plasmonic structures for upconversion enhancement.

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