Fabrication and applicationof plasmonic materials- Takeyasu group Faculty of Sciencetakeyasu@okyama-u.ac.jp

Research activities
1) Self-assembly/growth for metallic nanostructures
1) Plasmon-induced chemical reaction2) Surface-enhanced Raman scattering (SERS)

Self-assembly/growth for metallicnanostructures
Metallic nanostructures show interesting optical properties because ofsurface plasmon polaritons. These structures are applicable to opticalfilters, sensing method, index control, and so on. The optical properties aredetermined also by the shape in nanoscale. For practical applications, it isdesired to fabricate such metallic nanostructure over bulk scales.
Objective: Self-assembly/growth for such metallic nanostructure with awide variety of shapes

Au nanoparticle array

Ag nano-tree

R. Kagawa, N. Takeyasu, T. Kaneta, Y. Takemoto, Appl. Phys. Express 9, 075003 (2016). Au nano-dimer
N. Takeyasu, N. Taguchi, N. Nishimura, B.H. Cheng, S. Kawata, APL Photonics 1, 050801 (2016).
S. Ikegami, N. Takeyasu, T. Tanaka, T. Kaneta, (submitted).

An innovative and low cost method to growsmooth thin films of gold nanoparticles

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Plasmon-induced chemical reaction
Light can be enormously enhanced at the surface of nanometals: this crucial property was used in plasmon-induced chemical
reaction, surrface-enhanced spectroscopy, etc.
Objectives: Investigation of plasmon-induced chemical reactionsabpara-Aminothiophenol (p-ATP) wasmeasured on AgNP array. It wasobserved that chemical reaction
from p-ATP to dimercaptoazobenzene (DMAB) was induced
during SERS measurement.

Raman peaks of DMAB were observed at 1140, 1390 and 1430 cm-1. The
peak intensity ratios were plotted with different laser powers at (a)1140 cm-1
and (b)1430 cm-1 (compared to the peak at 1180cm-1). From these results, it
was estimated that the chemical reaction from p-ATP to DMAB occurs at morethan ~0.028 mW.
N. Takeyasu, et al., J. Phys. Chem. C 120, 12163 (2016).

Surface-enhanced Raman scattering (SERS)Light can be enormously enhanced at the surface of nanometals, which enables high-sensitive chemical sensing.
However, it was afraid that some analytes, for instance, p-ATP, weretransformed into different molecules during SERS measurement.

Objectives: Development of high-sensitive analytical method

SERS spectrum of Rhodamine6G on
silver nano-trees. Fluorescence wasquenched, and the signals wereenhanced by ~5×106.

para-Aminothiophenol (p-ATP)
was measured on AuNP arraycovered with thin SiO2, which
was effective to prevent thechemical reaction.

N. Takeyasu, et al., APL Photonics 1, 050801 (2016).
N. Takeyasu, K. Yamaguchi, R. Kagawa, T. Kaneta, F. Benz, M.Fujii, J. J. Baumberg (submitted).

Takeyasu Gr. International Projects
ASCENTOkayama University researcher: Pr. Takeyasu
Tyndall researcher : Dr. Mircea Modreanu <mircea.modreanu@tyndall.ie
Coordinator : Dr. Nicolas Cordero Nicolas.Cordero@tyndall.ie"Characterisation of 2D metal nanoparticle array"
We have been working on surface-enhanced Raman scattering/spectroscopy (SERS). Noble metallic
nano-surface are required for SERS substrate. We are developing the SERS substrate now.
Gold/silver nano-particle arrays (single layer) have been shown to work as excellent SERS substrates
exhibiting Raman enhancement of 10^4 ~ 10^5.

To increase the enhancement, we would like to make double layer andevaluate the optical properties ---- Job performed at Tyndall in April 2017.

Specific gain expected at ASCENT (Tyndall) platforms
Raman microscope equipped with a 633 nm excitation laser at Tyndall – 532 & 785 nm at OU.
Only silver nanoparticle array has been used so far.
The 633 nm laser allows using gold nanoparticle single/ double layer as SERS substrate.

Takeyasu Gr. Members (y-2017)
1 MD student (Metafluid)
2 BD students (SERS, nano-dimer)International students

1 internship student (MD), Grenoble-Alpes University – France Duration: May 2017 - Aug. 2017
* Thermal deformation of Au nanorod

Recent papers
1) R. Kagawa, N. Takeyasu, T. Kaneta, Y. Takemoto, “Oil-in-water emulsion as fabrication
platform for uniform plasmon-controlled two-dimensional metallic nanoparticle array,” Appl.
Phys. Express 9, 075003 (2016).
2) N. Takeyasu, R. Kagawa, K. Sakata, T. Kaneta, “Laser Power Threshold of ChemicalTransformation on Highly Uniform Plasmonic and Catalytic Nanosurface,” J. Phys. Chem. C120, 12163 (2016).
3) Invited Article: N. Takeyasu, N. Taguchi, N. Nishimura, B.H. Cheng, S. Kawata, “Plasmonicgrowth of patterned metamaterials with fractal geometry,” APL Photonics 1, 050801 (2016).