Wafer-Scale LSPR Substrate: Oblique Deposition of Gold on a Patterned Sapphire Substrate.

Kihyeun Kim,Na Rae Jo,Yong-Beom Shin,Eun-Jung Jo,Min-Gon Kim,Ki Joong Lee

doi:10.3390/bios12030158

Abstract

Label-free detection of biomolecules using localized surface plasmon resonance (LSPR) substrates is a highly attractive method for point-of-care (POC) testing. One of the remaining challenges to developing LSPR-based POC devices is to fabricate the LSPR substrates with large-scale, reproducible, and high-throughput. Herein, a fabrication strategy for wafer-scale LSPR substrates is demonstrated using reproducible, high-throughput techniques, such as nanoimprint lithography, wet-etching, and thin film deposition. A transparent sapphire wafer, on which SiO2-nanodot hard masks were formed via nanoimprint lithography, was anisotropically etched by a mixed solution of H2SO4 and H3PO4, resulting in a patterned sapphire substrate (PSS). An LSPR substrate was finally fabricated by oblique deposition of Au onto the PSS, which was then applied to label-free detection of the binding events of biomolecules. To the best of our knowledge, this paper is the first report on the application of the PSS used as an LSPR template by obliquely depositing a metal.

Highlights

Localized surface plasmon resonance (LSPR), which occurs in metal nanostructures, has attracted considerable attention from various optical- and electrical-based research fields, such as optical biosensors, color engineering, spectroscopy, metamaterials, and plasmonic optoelectronics [1–5]
We have suggested a fabrication method of wafer-scale localized surface plasmon resonance (LSPR) substrates by engineering a single crystal substrate and obliquely depositing Au, using highthroughput and high-reproducibility techniques
As a single crystal substrate, sapphire wafers were chosen because of their transparency, which is highly advantageous for optical applications, such as optical biosensors, metamaterials, and solar cells

Summary

Introduction

Localized surface plasmon resonance (LSPR), which occurs in metal nanostructures, has attracted considerable attention from various optical- and electrical-based research fields, such as optical biosensors, color engineering, spectroscopy, metamaterials, and plasmonic optoelectronics [1–5]. To fabricate LSPR substrates, two primary methods have been used until now: (i) the synthesis of metal nanoparticles (NPs), and covalent attachment of the NPs on substrates through self-assembled monolayers (SAMs) [9,10]; and (ii) the patterning of metal nanostructures by nanolithography techniques [7,11,12]. Regarding the former (i), various shapes of gold (Au) NPs were synthesized in a solution, such as spheres, rods, triangles, and spiked structures, which could tune LSPR properties depending on the shape [13,14]. Nanoimprint lithography enabled a high-throughput process and elaborate patterning, it encountered difficulties in the fabrication of various shapes of master molds, leading to limitations in the tuning of LSPR properties [24]

Methods

Results

Conclusion