Terahertz spectroscopic characterization of fractal silver nanoparticles

Terahertz meta-surface sensors integrated with silver nanoparticles have attracted attention since it was discovered that the interaction between terahertz waves and analytes to enhance the local electric field of silver nanoparticles. However, the cost of production of silver nanoparticles optimized for biosensor applications is high. In contrast, the silver tree-like fractal structures (AgTFs) with a fractal structure have the same structure over a wide range of wavelengths and are expected to exhibit light-single-particle interactions such as surface-enhanced Raman scattering over a wide range of wavelengths, making it feasible to realize biosensors with enhanced sensitivity over a wide range of wavelengths from the visible to the terahertz region. In this study, we used terahertz time-domain spectroscopy to characterize fabricated AgTFs in the terahertz region. Experimental results indicate that AgTFs with fractal structure have a resonance peak near 0.6 THz and that the resonance peak is altered by changing the solvent. This study shows that AgTFs can be used for terahertz biosensors.