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Open AccessFeature PaperArticle

Under-Etched Plasmonic Disks on Indium Tin Oxide for Enhanced Refractive Index Sensing on a Combined Electrochemical and Optical Platform

Interdisciplinary nanoscience center (iNANO), Aarhus University, 8000 Aarhus, Denmark
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Materials 2020, 13(4), 853; https://doi.org/10.3390/ma13040853
Received: 17 December 2019 / Revised: 28 January 2020 / Accepted: 12 February 2020 / Published: 13 February 2020
(This article belongs to the Special Issue Thin Films for Sensing Applications)
A simple approach to enhance the refractive index sensitivity of gold nanodisks immobilized on electrically conducting indium tin oxide (ITO) substrates has been demonstrated. A two-fold increase in sensitivity to bulk refractive index change was achieved by substrate under-etching of gold nanodisks on ITO in 50 mM sulfuric acid. The influence of an intermediate titanium adhesion layer was investigated and was found to markedly influence the etching pattern and time. Etching with an adhesion layer resulted in enhanced refractive index sensitivity on disk-on-pin like structures after long etching times, whereas etching of disks deposited directly on ITO resulted in a disk-on-pincushion like configuration and similarly enhanced sensitivity already at shorter times. The gold disks remained electrically connected to the ITO substrate throughout etching and allowed site-specific electrodeposition of poly(3-aminophenol) at the nanodisks, showing enhanced thin-film refractive index sensitivity. This work demonstrates a simple method for enhancing refractive index sensitivity of nanostructures on ITO substrates for combined electrochemical and optical platforms, and subsequently a method to modify the surface of the electrically connected nanostructures, which has potential application in biosensing.
Keywords: plasmonics; refractive index sensor; colloidal lithography plasmonics; refractive index sensor; colloidal lithography
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MDPI and ACS Style

Dyrnesli, H.; Klös, G.; Sutherland, D.S. Under-Etched Plasmonic Disks on Indium Tin Oxide for Enhanced Refractive Index Sensing on a Combined Electrochemical and Optical Platform. Materials 2020, 13, 853.

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