講演情報
[10a-N203-9]Terahertz characterization of silver nanoparticles with fractal structures in polymethyl methacrylate films
〇Sota Itayama1, Tomoki Kawahara1, Jin Wang1, Takeyasu Nobuyuki1, Kiwa Toshihiko1 (1.Okayama Univ.)
キーワード：
terahertz、silver nanoparticles、metamaterial
Terahertz (THz) radiation is highly promising for biosensing because it is non-ionizing and couples directly to collective biomolecular vibrations. Conventional THz detectors, however, still suffer from limited signal reliability and sensitivity. Metamaterial coatings that concentrate local THz fields offer a viable remedy, and self-grown silver nanoparticle tree-like fractal structures (AgTFs) are particularly attractive: they deliver broadband THz responses, can be produced rapidly at scale, and can be deposited over large areas for wall-scale sensors. Tanaka et al. [1] observed a solvent-dependent THz peak from AgTF powders dried on quartz substrates, but their spectra were degraded by thickness artefacts and by the restricted 0.1–2 THz measurement window. In the present work, AgTF powders synthesised in acetone, ethanol, and a 1:1 acetone–ethanol mixture were dispersed in polymethyl-methacrylate (PMMA) and cast into uniform 13 mm-diameter, 0.1 mm-thick films, which were characterised with a broadband 0.5–5 THz time-domain spectrometer. Ethanol films exhibited resonances at 0.91 and 1.62 THz, acetone films at 3.98 THz, and mixed-solvent films at 1.48 and 4.23 THz. These solvent-dependent shifts correlate with solvent viscosity and the branch widths observed by SEM: finer branches support lower-frequency modes, whereas coarser branches raise the resonance. Controlling solvent viscosity therefore provides a straightforward means of tuning the THz response of AgTFs, underscoring their potential for low-cost, large-area THz biosensing.