Reproducible Plasmonic Nanopyramid Array of Various Metals for Highly Sensitive Refractometric and Surface-Enhanced Raman Biosensing

Abstract

Localized surface plasmon resonance (LSPR) biosensors show great potential for practical/commercial use in clinical diagnosis, home healthcare, environmental analysis, and public healthcare. However, two main issues, that is, low refractometric sensitivity and low reproducibility (large-area uniformity and batch-to-batch consistency), hinder the extensive applications of LSPR biosensors. Therefore, plasmonic nanostructures with high sensitivity and excellent reproducibility are desirable for preparing reliable LSPR sensors. Herein, we have fabricated plasmonic nanopyramid arrays (NPAs) for several batches with reproducible morphology and optical properties by elastic soft lithography and metal thermal evaporation. NPAs of various metals (i.e., Al, Au, and Ag) were also prepared by thermal evaporation with the according metals. The transmission spectra of these NPAs showed several narrow LSPR peaks in the visible-infrared wavelength region. The refractometric sensitivities of the LSPR peaks were systematically studied, and high refractometric sensitivities of 774.0, 472.8, and 421.0 nm/RIU were achieved on Al, Au, and Ag NPAs, respectively. To demonstrate the potential of the NPAs for multiplex applications, we first applied this highly sensitive Al NPA biosensor to monitoring the process of proliferation of HeLa cancer cells, in situ and in real time. Then, we demonstrated that the Au NPA was able to identify the absorbed analytes on its surface through the surface-enhanced Raman scattering spectrum. In addition, the finite difference time domain simulations were performed to reveal the electromagnetic field enhancement on NPAs. Because of the properties of high sensitivity and excellent reproducibility of the metal NPA LSPR substrates, as well as the simplicity and cost efficiency of the fabrication method, our proposed work will accelerate the practical use of LSPR sensors.

High‐Aspect‐Ratio Nanostructured Surfaces as Biological Metamaterials

“…Surface‐enhanced Raman spectroscopy relies upon roughened or vertically structured surfaces to induce the appropriate effect, making high‐aspect‐ratio nanostructured surfaces decorated with metallic nanoparticles well suited to this technique. This approach has been used extensively in general biosensing applications, along with a few examples of direct cell interfacing.…”

Biosensing Applications Using Nanostructure-Based Localized Surface Plasmon Resonance Sensors

“…Deposition of nanomaterials on flat substrates can be achieved via annealing and deposition procedures using focused ion beams, holographic lithography, nanosphere lithography, elastic soft lithography, and template stripping [ 41 , 42 , 43 ]. Using this approach, diverse nanostructures, such as nanoshells, dimer/trimer nanoantennas, nanostars, nanocrescents, and nanopyramid arrays have been produced and deposited on diverse flat substrates [ 44 , 45 , 46 , 47 , 48 , 49 ]. Periodic nanopatterns can be fabricated using electron beam lithography or mask-assisted techniques, which render regular patterns such as nanoholes, nanofillars, and nanodisks [ 50 , 51 , 52 , 53 , 54 ].…”

Recent Progress in Optical Sensors for Biomedical Diagnostics

“…The sensor was fabricated using a composite of tungsten sulphide nanorod array on titanium mesh with DNA functionalised AuNPs (size = 18 ± 1 nm) as a sensor platform and a multiplexed signal amplifier in the form of a nanohybrid of AgNPs (lattice spacing = 0.27 nm) and zinc metal-organic framework nanozyme. Other geometries that have been widely explored in recent years for developing LSPR sensors include nanopyramids [95,104,105], nanourchins [106][107][108][109], nanocups [92,[110][111][112][113], nanoholes [114][115][116][117] and nanoislands [118][119][120][121][122].…”