Highly Sensitive Biosensing Using Arrays of Plasmonic Au Nanodisks Realized by Nanoimprint Lithography

Abstract

We describe the fabrication of elliptical Au nanodisk arrays as a localized surface plasmon resonance (LSPR) sensing substrate for clinical immunoassay via thermal nanoimprint lithography (NIL) and enhancement in the sensitivity of the detection of the prostate-specific antigen (PSA) using the precipitation of 5-bromo-4-chloro-3-indolyl phosphate p-toluidine/nitro blue tetrazolium (BCIP/NBT), catalyzed by alkaline phosphatase. Au nanodisks were fabricated on glass through an unconventional tilted evaporation, which could preserve the thickness of imprinted resists and create an undercut beneficial to the subsequent lift-off process without any damage to pattern dimension and the glass while removing the residual polymers. To investigate the optically anisotropic property of the LSPR sensors, a probe light with linear polarization parallel to and perpendicular to the long axis of the elliptical nanodisk array was utilized, and their sensitivity to the bulk refractive index (RI) was measured as 327 and 167 nm/RIU, respectively. To our knowledge, this is the first application of enzyme-substrate reaction to sandwich immunoassay-based LSPR biosensors that previously suffered from a low sensitivity due to the short penetration depth of the plasmon field, especially when large-sized antibodies were used as bioreceptors. As a result, a large change in local refractive index because of the precipitation on the Au nanodisks amplified the wavelength shift of the LSPR peak in the vis-NIR spectrum, resulting in femtomolar detection limits, which was ∼10(5)-fold lower than the label-free detection without the enzyme precipitation. This method can be extended easily to the other clinical diagnostics with a high sensitivity.

Plasmonic gold nanodiscs using piezoelectric substrate birefringence for liquid sensing

“…A sensitivity of 165 nm per refractive index unit (RIU) has been observed at the liquid mode λT and a sensitivity of 130 nm/RIU has been observed at the LiNbO3 mode λB. The sensitivity for the liquid mode is comparable to other similar SPR sensors on isotropic media with a resonance in the same wavelength range 18 -for these, the sensitivity increases for longer resonant wavelengths, 21 but this principle only applies due to the similarity of substrate and superstrate refractive indices and yields only one broad resonance: for our structure it does not hold true for the higher wavelength λB mode compared to λT. In essence, it can be inferred that it is the liquid (top) resonance mode λT which provides the high sensitivity and undergoes a sensitivity increase for longer wavelengths.…”

Ultrabroadband Metasurface for Efficient Light Trapping and Localization: A Universal Surface‐Enhanced Raman Spectroscopy Substrate for “All” Excitation Wavelengths

“…In recent years, extensive efforts have been focused on the development of inexpensive, large area SERS substrates with high enhancement factors (EFs), and reproducible, uniform responses. [3][4][5][6][7] Current dominant fabrication techniques include electron beam (e-beam) lithography, [ 8,9 ] nanoimprint, [10][11][12] self-assembled nanosphere, [13][14][15][16][17] hybrid volumes. Therefore, a single substrate can work for almost "all" available excitation wavelengths, which is particularly useful for sensing a broad spectrum of chemicals on the same chip.…”

Ecofriendly antiglare film derived from biomass using ultraviolet curing nanoimprint lithography for high-definition display

“…5 As an alternative to photolithography processes to obtain various nanostructures, ultraviolet curing nanoimprint lithography has been proposed and pursued in creating nanostructures. [6][7][8][9][10][11] Ultraviolet curing nanoimprint lithography has existed for several years and has demonstrated great potential for advanced electronic nanofabrication endeavors in the industrial production of many semiconductors, hard disk drive storage devices, light-emitting diodes, solar cell devices, actuators, biosensors, and microelectro mechanical systems. Ultraviolet curing nanoimprint lithography to yield optical structures is being pursued in optics and photonics to yield low-cost optical components.…”