Surface-Enhanced Raman Spectroscopy for Biomedical Applications: A Review

Surface-enhanced Raman scattering has recently become a powerful vibrational spectroscopic tool for numerous applications in physical, chemical, biological as well as medical science. Apart from a chemical enhancement process, plasmonic fields sustained by metal nanoparticles play a vital role in the surface enhancement phenomena. Thus most SERS based applications also involve metal nanostructures as substrates apart from the analyte molecules. High sensitivity, molecular selectivity, portability and low cost are some of the advantages of SERS over conventional spectroscopic methods that has led to its popularity. In particular, biomedical applications involving detection and sensing of biomolecules are now moving towards utilizing this new tool. This review provides an introduction of SERS for biomedical applications. The theory of SERS will be explained in the first section. A brief review on popular SERS substrates will be given in the subsequent section. The review will focus on certain biomedical applications such as glucose sensors, cancer detection and protein sensing using SERS

4f coherent imager system and its application to nonlinear optical measurements

International audienc

20th International Symposium on Optomechatronic Technology

This book presents peer-reviewed articles from the 20th International Symposium on Optomechatronic Technologies (ISOT 2019), held in Goa, India. The symposium brought together students, researchers, professionals, and academicians in the field of optomechatronics and related areas on a common platform conducive to academic interaction with business professionals

Shaping the optical response of nanoantennas

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Controlling the optical near field of nanoantennas with spatial phase-shaped beams

We report on a novel approach, based on sub-wavelength spatial phase variations at the focus of high-order beams, to reconfigure the optical near field distribution near plasmonic nanostructures. We first show how the introduction of phase jumps in the incident field driving a gap nanoantenna strongly affects its near field response. Beyond, we demonstrate the feasibility of exploiting this approach to selectively switch on and off hot-spots sites within a complex antenna architecture.4 page(s

Template-Stripped Tunable Plasmonic Devices on Stretchable and Rollable Substrates

We use template stripping to integrate metallic nanostructures onto flexible, stretchable, and rollable substrates. Using this approach, high-quality patterned metals that are replicated from reusable silicon templates can be directly transferred to polydimethylsiloxane (PDMS) substrates. First we produce stretchable gold nanohole arrays and show that their optical transmission spectra can be modulated by mechanical stretching. Next we fabricate stretchable arrays of gold pyramids and demonstrate a modulation of the wavelength of light resonantly scattered from the tip of the pyramid by stretching the underlying PDMS film. The use of a flexible transfer layer also enables template stripping using a cylindrical roller as a substrate. As an example, we demonstrate roller template stripping of metallic nanoholes, nanodisks, wires, and pyramids onto the cylindrical surface of a glass rod lens. These nonplanar metallic structures produced via template stripping with flexible and stretchable films can facilitate many applications in sensing, display, plasmonics, metasurfaces, and roll-to-roll fabrication.ISSN:1936-0851ISSN:1936-086

Optically-assisted thermophoretic reversible assembly of colloidal particles and E. coli using graphene oxide microstructures

International audienceOptically-assisted large-scale assembly of nanoparticles have been of recent interest owing to their potential in applications to assemble and manipulate colloidal particles and biological entities. In the recent years, plasmonic heating has been the most popular mechanism to achieve temperature hotspots needed for extended assembly and aggregation. In this work, we present an alternative route to achieving strong thermal gradients that can lead to non-equilibrium transport and assembly of matter. We utilize the excellent photothermal properties of graphene oxide to form a large-scale assembly of silica beads. The formation of the assembly using this scheme is rapid and reversible. Our experiments show that it is possible to aggregate silica beads (average size 385 nm) by illuminating thin graphene oxide microplatelet by a 785 nm laser at low intensities of the order of 50-100 µW/µm 2. We further extend the study to trapping and photoablation of E. coli bacteria using graphene oxide. We attribute this aggregation process to optically driven thermophoretic forces. This scheme of largescale assembly is promising for the study of assembly of matter under non-equilibrium processes, rapid concentration tool for spectroscopic studies such as surface-enhanced Raman scattering and for biological applications

Millimeter-Sized Suspended Plasmonic Nanohole Arrays for Surface-Tension-Driven Flow-Through SERS

We present metallic nanohole arrays fabricated on suspended membranes as an optofluidic substrate. Millimeter-sized suspended nanohole arrays were fabricated using nanoimprint lithography. We demonstrate refractive-index-based tuning of the optical spectra using a sucrose solution for the optimization of SERS signal intensity, leading to a Raman enhancement factor of 10⁷. Furthermore, compared to dead-ended nanohole arrays, suspended nanohole arrays capable of flow-through detection increased the measured SERS signal intensity by 50 times. For directed transport of analytes, we present a novel methodology utilizing surface tension to generate spontaneous flow through the nanoholes with flow rates of 1 μL/min, obviating the need for external pumps or microfluidic interconnects. Using this method for SERS, we obtained a 50 times higher signal as compared to diffusion-limited transport and could detect 100 pM 4-mercaptopyridine. The suspended nanohole substrates presented herein possess a uniform and reproducible geometry and show the potential for improved analyte transport and SERS detection

Template-Stripped Tunable Plasmonic Devices on Stretchable and Rollable Substrates

We use template stripping to integrate metallic nanostructures onto flexible, stretchable, and rollable substrates. Using this approach, high-quality patterned metals that are replicated from reusable silicon templates can be directly transferred to polydimethylsiloxane (PDMS) substrates. First we produce stretchable gold nanohole arrays and show that their optical transmission spectra can be modulated by mechanical stretching. Next we fabricate stretchable arrays of gold pyramids and demonstrate a modulation of the wavelength of light resonantly scattered from the tip of the pyramid by stretching the underlying PDMS film. The use of a flexible transfer layer also enables template stripping using a cylindrical roller as a substrate. As an example, we demonstrate roller template stripping of metallic nanoholes, nanodisks, wires, and pyramids onto the cylindrical surface of a glass rod lens. These nonplanar metallic structures produced <i>via</i> template stripping with flexible and stretchable films can facilitate many applications in sensing, display, plasmonics, metasurfaces, and roll-to-roll fabrication