Near-Field Spot for Localized Light-Excitation of a Single Fluorescent Molecule
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Near-Field Spot for Localized Light-Excitation of a Single Fluorescent Molecule Muhammad Shemyal NISAR1, Yujun CUI1, Kaitong DANG1, Liyong JIANG2, and Xiangwei ZHAO1* 1
State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University,
Nanjing 210096, China 2
Department of Physics, School of Science, Nanjing University of Science and Technology, Nanjing 210094, China
*
Corresponding author: Xiangwei ZHAO
E-mail: [email protected]
Abstract: Zero-mode waveguides have become important tools for the detection of single molecules. There are still, however, serious challenges because large molecules need to be packed into nano-holes. To circumvent this problem, we investigate and numerically simulate a novel planar sub-wavelength 3-dimension (3D) structure, which is named as near-field spot. It enables the detection of a single molecule in highly concentrated solutions. The near-field spot can produce evanescent waves at the dielectric/water interface, which exponentially decay as they travel away from the dielectric/water interface. These evanescent waves are keys for the detection of fluorescently tagged single molecules. A numerical simulation of the proposed device shows that the performance is comparable with a zero-mode waveguide. Additional degrees-of-freedom, however, can potentially supersede its performance. Keywords: Plasmonics; single fluorescence molecule; evanescent field; zero-mode waveguide Citation: Muhammad Shemyal NISAR, Yujun CUI, Kaitong DANG, Liyong JIANG, and Xiangwei ZHAO, “Near-Field Spot for Localized Light-Excitation of a Single Fluorescent Molecule,” Photonic Sensors, DOI: 10.1007/s13320-020-0593-2.
1. Introduction Single molecule fluorescence (SMF) is a key technology for many applications in molecular biology, molecular kinetics [1–3], transient intermediates for chemical or biochemical reactions [4, 5], deoxyribonucleic acid (DNA) sequencing[6, 7], diagnostics[8, 9], and personalized medicine [10, 11]. Generally, there are two means to improve the signal to noise ratio (SNR) by using SMF. One way is to reduce the intrinsic background fluorescence (typically) via chemical means. The other method is to reduce the excitation volume such that less background noise Received: 6 October 2019 / Revised: 12 June 2020 © The Author(s) 2020. This article is published with open access at Springerlink.com DOI: 10.1007/s13320-020-0593-2 Article type: Regular
is generated by physical methods. For example, laser scanning confocal microscopy (LSCM) [12, 13], total internal reflection microscopy (TIRF) [14, 15], waveguide evanescent field fluorescence microscopy [16, 17], two-photon microscopy[18], and stimulated emission depletion (STED) microscopy[19] use optical settings to confine the excitation to a very small volume. There are also other techniques that use nanostructures for the localized excitation of fluorescence, for example, Raman-signal-like scanning near-field optical microscopy (SNOM) [20], tip enhanced Raman scattering (TERS) [21], optic
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