Multilayer thin-film flake dispersion gel for surface-enhanced Raman spectroscopy
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ORIGINAL ARTICLE
Multilayer thin‑film flake dispersion gel for surface‑enhanced Raman spectroscopy Samir Kumar1 · Misa Kanagawa1 · Kyoko Namura1 · Takao Fukuoka1 · Motofumi Suzuki1 Received: 12 June 2020 / Accepted: 19 September 2020 © King Abdulaziz City for Science and Technology 2020
Abstract Ag nanorod arrays/dielectrics/mirror-structured multilayer thin films are well-known, sensitive surface-enhanced Raman scattering (SERS) substrates that enhance the Raman scattering cross section by the interference of light. However, it is difficult to extract biomarkers directly from human skin using these solid substrates. To overcome this problem, we propose a multilayer thin-film flake dispersion gel by centrifugal mixing of the multilayer thin film and hydroxyethyl cellulose (HEC) gel. The multilayer thin film was prepared by serial bideposition using the dynamic oblique angle deposition technique. The mixing process was optimized to obtain flakes of ~ 10 μm so that the optical properties of the multilayer film can be preserved, and there is no risk of adverse effects on humans. The SERS characteristics of the flakes dispersion gel were tested using 4, 4′-bipyridine (BPY). The BPY molecules diffused through the highly porous gel within seconds, producing significant SERS signals. The multilayer thin-film flakes dispersion gel showed a SERS signal approximately 20 times better than the gel-dispersed Ag nanorod arrays without a multilayer film structure. These SERS active flakes dispersion gel can be used directly on the skin surface to collect body fluids from sweat, for biomarker sensing. Keywords Ag nanorods · Surface-enhancing Raman scattering · Hydroxyethylcellulose gel · Dynamic oblique angle deposition
Introduction Localized plasmon resonance can be excited when the light of a specific wavelength is incident on a noble metal nanoparticle.(Bochenkov et al. 2015; Kosuda et al. 2016) This enhances the electric field around the nanoparticles and enables surface-enhanced Raman scattering (SERS).(Moskovits 1985; Kruszewski 1998; Deng et al. 2013) SERS has been a growing area of interest in materials science, biophysics, medical diagnostics, and molecular biology as it enables the label-free detection and identification of molecules.(Hughes Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13204-020-01562-0) contains supplementary material, which is available to authorized users. * Samir Kumar [email protected] Motofumi Suzuki m‑[email protected]‑u.ac.jp 1
Department of Micro Engineering, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615‑8540, Japan
et al. 2014; Kumar et al. 2015, 2020b; Sivashanmugan et al. 2019) With the rapid development of medical and chemical fields, efforts have recently been dedicated to the practical use of biosensors using SERS.(Petry et al. 2003; Harper et al. 2013; Schlücker 2014; Pu et al. 2017). A variety of SERS substrates have been reported, ranging from rough metal surfaces to fractals, nanowire
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