Advanced Large-Scale Nanofabrication Route for Ultrasensitive SERS Platforms Based on Precisely Shaped Gold Nanostructures

Suzanna Akil,Safi Jradi,Rana Omar,Vladimir Shur,Aotmane En Naciri,Dmitry Kuznetsov

doi:10.3390/nano11071806

Abstract

One of the key issues for SERS-based trace applications is engineering structurally uniform substrates with ultrasensitivity, stability, and good reproducibility. A label-free, cost-effective, and reproducible fabrication strategy of ultrasensitive SERS sensors was reported in this work. Herein, we present recent progress in self-assembly-based synthesis to elaborate precisely shaped and abundant gold nanoparticles in a large area. We demonstrated that shape control is driven by the selective adsorption of a cation (Na+, K+, and H+) on a single facet of gold nanocrystal seeds during the growth process. We studied SERS features as a function of morphology. Importantly, we found a correlation between the shape and experimental SERS enhancement factors. We observed a detection threshold of 10−20 M of bipyridine ethylene (BPE), which matches the lowest value determined in literature for BPE until now. Such novel sensing finding could be very promising for diseases and pathogen detection and opens up an avenue toward predicting which other morphologies could offer improved sensitivity.

Highlights

As the restoring force on the conduction electrons is extraordinarily sensitive to the particle curvature, non-spherical metallic nanoparticles (MNPs) produced via various approaches [1,2,3] have been found to shift their surface plasmon frequency drastically, making them useful as multicolor diagnostic labels and for other optical devices [4]
In previous works, [26,27,28,29] we focused on the understanding of PMMA self-assembly via vapor induced phase separation (VIPS) in order to fabricate MNPs
It was concluded that the silver precursor concentration, substrate chemistry, and the thermal treatment of the substrate are the main factors which rule the synthesis process

Summary

Introduction

As the restoring force on the conduction electrons is extraordinarily sensitive to the particle curvature, non-spherical metallic nanoparticles (MNPs) produced via various approaches [1,2,3] have been found to shift their surface plasmon frequency drastically, making them useful as multicolor diagnostic labels and for other optical devices [4]. Recent studies showed that turnover rates and selectivity of catalytic reactions can be strongly influenced by the shape of the NPs since their surface structures and active sites are tailored at the molecular level. In addition to colloidal approaches, new methods have been proposed to synthesize non-spherical NPs. Abid et al showed that silver NPs can be synthesized by various irradiation methods. Laser irradiation of aqueous solution of a silver salt and surfactant yields silver NPs with suitable shapes and sizes [11]

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