【研究成果】2016年-

研究成果99

Plasmonic growth of patterned metamaterials with fractal geometry
Nobuyuki Takeyasu, Natsuo Taguchi, Naoki Nishimura, Bo Han Cheng, and Satoshi Kawata
APL PHOTONICS 1, 050801 (2016)

We have developed a self-growing method of metallic metamaterials that exhibit fractal geometry with self-similarity. Plasmonic heating with UV light illumination triggers the growth at seeds and needle tips. Silver nano-trees are grown in silver ion solution due to the diffusion of ions and reduction of silver crystals. No use of surfactant helps to form trees with branches and sub-branches. We described the protocol of the self-growth fabrication and analyzed the fractal dimensions of the structures. An application of the developed structures was shown through experiments of surface enhanced Raman sensing of molecules with large enhancement due to its fractal nature.


Enhanced Raman spectroscopy of Rhodamine 6G (R6G) molecules using silver nano-trees. (a) SEM image of the grown silver nano-trees. The scale bar is 500 μm. (b) Fluorescence microscope image of (a) covered with R6G (10 μM) aqueous solution. The fluorescence from R6G is quenched by the silver nano-trees, resulting in a dark star pattern. (c) SERS spectrum of R6G on the silver nano-trees obtained in the red circle area in (a) and (b). Strong Raman peaks assigned to vibrational modes of R6G are clearly observed, which can be attributed to the large enhancement effects provided by the silver nano-trees. (d) Same as (c) but taken on a different area without the silver nano-trees denoted by the green circle area in (a) and (b). For both measurements, the exposure time was 1 sec, and the laser power was 1.0 and 0.13 mW, respectively.