Fabrication Strategies of 3D Plasmonic Structures for SERS
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Review Article
Fabrication Strategies of 3D Plasmonic Structures for SERS Seungki Lee1 & Inhee Choi
1,
*
Received: 10 January, 2019 / Accepted: 18 February, 2019 / Published online: 08 March, 2019 â’¸The Korean BioChip Society and Springer 2019
Abstract Recent advancements in fabricating plasmonic nanostructures have markedly lessened the limitations of conventional optical sensors, in terms of sensitivity, tunability, photostability, and in vivo applicability. The sophisticated design of diverse metallic nanoparticles and formation of two- or threedimensional (3D) assemblies have enhanced the performance of plasmon-based sensing and imaging applications. Especially, the creation of highly localized electromagnetic fields (i.e., hot-spots) in the multidimensional plasmonic structures has enabled ultrasensitive detection of biomolecules at low concentrations via surface-enhanced Raman scattering (SERS). In this review, we summarize representative approaches to obtain 3D plasmonic structures categorized by the fabrication strategies. These include colloidal synthesis of plasmonic nanoparticles with multiple hot-spots and post-integration of the nanoparticles into 3D templates, and self-integration in the course of constructing 3D structures. We also describe notable structural benefits in sensing applications, especially for SERS, that take advantages of such 3D plasmonic nanostructures. Keywords: Plasmonic nanoparticles, Plasmonic nanostructures, Hot-spots, Surface enhanced Raman scattering, Three-dimensional assembly
Introduction Numerous approaches for fabricating metallic nanostructures have been introduced and utilized for various 1
Department of Life Science, University of Seoul, Seoul 02504, Republic of Korea *Correspondence and requests for materials should be addressed to I. Choi ( [email protected])
optical sensing and imaging applications. The collective oscillation of free electrons on noble metallic nanostructures induces surface plasmon resonance and intense electromagnetic (EM) fields. The result is the enhancement of optical signals, such as Raman scattering 1 and fluorescence2,3. Raman scattering, which features inelastic scattering of photons by the molecules, provides molecular specific fingerprint spectra. However, such Raman signals are usually too weak to be measured for low concentrations of analytes. To overcome this limitation, various plasmonic nanostructures have been utilized to obtain surfaceenhanced Raman scattering (SERS) signals4-7. SERS is a powerful plasmon-enhanced detection method that has broad applicability in many fields including biomedical8,9, environmental10,11, and food safety12,13. For SERS signal amplification, well- designed plasmonic nanoparticles and/or their controlled assembly techniques are necessary to create strong EM hot-spots in individual nanoparticles or between the nanoparticles. Studies have reported colloidal assemblies14,15 and two-dimensional (2D) arrays16,17 of the plasmonic nanoparticles as a way of generating abundant hot-spots and to collect s
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