Micro-cones Array-Based Plasmonic Metasurface for Sensitive and Enhanced Raman Detection
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Micro-cones Array-Based Plasmonic Metasurface for Sensitive and Enhanced Raman Detection Songya Cui 1
&
Chengxiang Tian 1 & Yarong Su 2 & Jiaguo Tian 1 & Yongqi Fu 1
Received: 2 March 2020 / Accepted: 29 June 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We report a micro-cone unit-based plasmonic metasurface for surface-enhanced Raman spectroscopy. The unit consists of Au cone-shaped needle, Au thin film, and SiO2 substrate. To verify performance of the structure for surface-enhanced Raman scattering (SERS) detection, both theoretical and experimental studies are performed. Highly efficient coupling conditions satisfied by the structure, ∇Φ > k0, the metasurface can realize the SERS measurement with detection limit and analytical enhancement factor (AEF) as high as 10−8 M and 109, respectively. With concentrations of benzenethiol ranging from 10−2 down to 10−8 M, the ratio of Raman intensity Iω2/Iω1 increases from 0.6 to 0.85 and Iω3/Iω1 from 0.9 to 1.3. This structure can provide a new insight for biosensing and biochemistry analyses. Keywords Micro-cone-like unit . Plasmonic metasurface . SERS . Benzenethiol . AEF
Introduction Since the first surface enhanced Raman scattering (SERS) phenomenon was observed at the end of last century, the related study becomes a hot research field. Many different explanations regarding mechanism of SERS from both physical (electromagnetic enhancement) and chemical (chemistry enhancement) point of views appear such as micro-rod effect model, surface mirror field model, surface plasmon resonance (SPR) theory, charge transfer model, and active site model [1–8]. Meanwhile, great efforts were made for preparation of wide range of “SERS substrates” (actually, they are metallic nanostructures that support SERS). And numerous different metallic structures were reported for the purpose of improving SERS signal intensity, e.g., noble metal surfaces [9], gold electrodes [10], fiber facetbased optical antenna arrays [11], Ag nanostructures on silica spheres [12], shell-isolated nanoparticle [13], metamaterials [14], gold nanotriangles [15], and colloidal gold nanostars
* Yongqi Fu [email protected] 1
2
[16]. These structures can be fabricated using electrolessplating method [17], self-assembled monolayer [18, 19], Au thin film is deposited [20], and focused ion beam milling [21]. However, the metal materials employed in the literature will cause large optical loss during propagation due to their large optical absorption of the metal surfaces (it is determined by imaginary part of permittivity of metal materials) which convert the optical energy into heat loss. In this paper, we report a new functional artificial material: a micro-cone unit-based plasmonic metasurface, for SERS detection. The Au micro-cone array can excite surface plasmon resonance (SPR) wave propagating along the conical needles to apex area. Therefore, this metasurface has small optical loss with special deign [22]. The plasmonic metasurface has advantages of two-dimensional stru
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