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Proceedings Paper

Orientation sensors by defocused imaging of single gold nano-bipyramids
Author(s): Fanwei Zhang; Qiang Li; Wenye Rao; Hongjin Hu; Ye Gao; Lijun Wu
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Paper Abstract

Optical probes for nanoscale orientation sensing have attracted much attention in the field of single-molecule detections. Noble metal especially Au nanoparticles (NPs) exhibit extraordinary plasmonic properties, great photostability, excellent biocompatibility and nontoxicity, and thereby could be alternative labels to conventional applied organic dyes or quantum dots. One type of the most interesting metallic NPs is Au nanorods (AuNRs). Its anisotropic emission accompanied with anisotropic shape is potentially applicable in orientation sensing. Recently, we resolved the 3D orientation of single AuNRs within one frame by deliberately introducing an aberration (slight shift of the dipole away from the focal plane) to the imaging system1 . This defocused imaging technique is based on the electron transition dipole approximation and the fact that the dipole radiation exhibits an angular anisotropy. Since the photoluminescence quantum yield (PLQY) can be enhanced by the “lightning rod effect” (at a sharp angled surface) and localized SPR modes, that of the single Au nano-bipyramid (AuNB) with more sharp tips or edges was found to be doubled comparing to AuNRs with a same effective size2. Here, with a 532 nm excitation, we find that the PL properties of individual AuNBs can be described by three perpendicularly-arranged dipoles (with different ratios). Their PL defocused images are bright, clear and exhibit obvious anisotropy. These properties suggest that AuNBs are excellent candidates for orientation sensing labels in single molecule detections.

Paper Details

Date Published: 2 January 2018
PDF: 7 pages
Proc. SPIE 10456, Nanophotonics Australasia 2017, 104564W (2 January 2018); doi: 10.1117/12.2283374
Show Author Affiliations
Fanwei Zhang, South China Normal Univ. (China)
Qiang Li, South China Normal Univ. (China)
Wenye Rao, South China Normal Univ. (China)
Hongjin Hu, South China Normal Univ. (China)
Ye Gao, South China Normal Univ. (China)
Lijun Wu, South China Normal Univ. (China)

Published in SPIE Proceedings Vol. 10456:
Nanophotonics Australasia 2017
James W. M. Chon; Baohua Jia, Editor(s)

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