Photo-polymerizable gold nanorods / methyl methacrylate composite for plasmonic optical application
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Photo-polymerizable gold nanorods / methyl methacrylate composite for plasmonic optical application Kyoko Masui1,2, Satoru Shoji1, Xuan-Ming Duan2, and Satoshi Kawata1 2
1 Department of Applied Physics, Osaka University, Osaka 565-0871, Japan, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, China [email protected] / http://lasie.ap.eng.osaka-u.ac.jp/
ABSTRACT We prepared a photo-polymerizable compound of Au nanorods and methyl methacrylate (MMA). An irradiation of ultraviolet (UV) light onto the compound induces photopolymerization of MMA, resulting in a formation of an Au nanorods/PMMA composite. Au nanorods were synthesized by seed-mediated growth method in aqueous solution. Hydrophobically functionalized Au nanorods were dispersed into MMA with a small amount of photosensitizer and initiator. We investigated the stability and the uniformity of the dispersion of Au nanorods during the photo-polymerization process through VIS-NIR absorption spectroscopy. We also demonstrated the use of the compound for two-photon micro/nanolithography. INTRODUCTION Recently noble metal nanoparticles and their arrangement are recognized as fundamental platforms of novel optical/photonic technologies. Varieties of applications, such as optical sensors, super-resolution imaging, metamaterials, optical nano-waveguides, etc. are proposed based on the excitation, transformation, and detection of local surface plasmon polaritons (LSPPs) through an interaction of photons and metal nanoparticles. Currently, for the achievement of such plasmonic technologies, one of the urgent demands is to develop novel micro/nano-fabrication methods to provide three-dimensional (3D) complex microstructures in which metal nanoparticles are embedded in desired orientation and arrangement. Aiming this purpose, we developed a gold nanorods/methyl methacrylate (MMA) compound, which makes it possible to produce arbitrary 3D micro/nano-structures of Au nanorods/PMMA composite. Our produced compound shows good stability of the dispersion of Au nanorods in MMA before / after photo-polymerization. Fabrication of Au nanorod/PMMA composite microstructures is demonstrated by means of two-photon lithography. Our approach could be a variable method for the development of novel plasmonic devices and metamaterials. PREPARATION OF GOLD NANORODS / METHYL METHACRYLATE COMPOUND The procedure of the preparation of Au nanorods/MMA compound is shown in Figure 1. Au nanorods were prepared by seed-mediated method [1,2]. The synthesis started from small gold seeds, and by the anisotropic protection of the surface of the gold particles by the surfactant
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hexadecyltrimethylammonium bromide (CTAB), the individual gold particle grew into a rod shape. Figure 2 shows scanning electron microscope (SEM) images of the Au nanorods dried on a glass substrate. Nanorods with a quite uniform geometrical shape and size (a thickness of 15 nm and a length of 60 nm) were obtained. Because of their shape uniformity, aggregations of self-aligned nanorods were
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