4.6 Article

Extraordinary sensitivity enhancement of Ag-Au alloy nanohole arrays for label-free detection of Escherichia Coli

Journal

BIOMEDICAL OPTICS EXPRESS
Volume 12, Issue 5, Pages 2734-2743

Publisher

OPTICAL SOC AMER
DOI: 10.1364/BOE.420828

Keywords

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Funding

  1. National Research Foundation of Korea [2016R1A2B301306115]
  2. PiQuant Inc.

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Silver-gold alloy nanohole arrays demonstrate enhanced refractive index sensitivity and long-term stability for ultra-sensitive plasmonic label-free detection of Escherichia coli, providing a new outlook for widely applicable biosensing and bio-medical applications.
Alloy nanostructures unveil extraordinary plasmonic phenomena that supersede the mono-metallic counterparts. Here we report silver-gold (Ag-Au) alloy nanohole arrays (alpha NHA) for ultra-sensitive plasmonic label-free detection of Escherichia Coli (E. coli). Large-area alpha-NHA were fabricated by using nanoimprint lithography and concurrent thermal evaporation of Ag and Au. The completely miscible Ag-Au alloy exhibits an entirely different dielectric function in the near infra-red wavelength range compared to mono-metallic Ag or Au. The alpha-NHA demonstrate substantially enhanced refractive index sensitivity of 387 nm/RIU, surpassing those of Ag or Au mono-metallic nanohole arrays by approximately 40%. Moreover, the alpha-NHA provide highly durable material stability to corrosion and oxidation during over one-month observation. The ultra-sensitive alpha-NHA allow the label-free detection of E. coil in various concentration levels ranging from 10(3) to 10(8) cfu/ml with a calculated limit of detection of 59 cfu/ml. This novel alloy plasmonic material provides a new outlook for widely applicable biosensing and blo-medical applications. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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