1. GOLD NANOPARTICLE PATTERNING BY SELF-ASSEMBLY AND TRANSFER FOR LSPR BASED SENSING
T. Ozaki, K. Sugano, T. Tsuchiya, O. Tabata
Department of Micro Engineering, Kyoto University
, Kyoto, JAPAN
ADVISER: Dr .CHENG-SHINE-LIU
REPORTER: SRINIVASU V P & HSIEH,HSIN-YI
STUDENT ID: &

2. OUTLINE Abstract Introduction Process overview
Template assisted self assembly
Results and discussion
Transfer of nanoparticles
LSPR characteristics of assembled Nanoparticle patterns
Conclusion

3. Abstract Pattern formation Dot and line pattern
Assembled particle pattern transfer
Localized Surface Plasmon Resonance (LSPR)

4. Introduction Characteristics of nanoparticles
Conventional nanopatterning techniques
Advantages of proposed method
60-nm diameter gold nanoparticles

5. PROCESS OVERVIEW
1) Self-assembly step
2)Transfer step

6. Template assisted self assembly
Mechanism of TASA
Aqueous particle dispersion
Capillary force

7. Result and discussion Effect of cross sectional shape
Relation between yield and concentration
The self-assembly yield is defined as the ratio of the total dot-patterned area to the properly assembled area.

8. SEM images of each cross-section before resist removal
SEM images of each cross-section before resist removal. Shape A, B and Shape C were fabricated by SF6 and CF4 dry etching, respectively.

9. concentration of particle dispersion and a yield of self-assembly.
Relation between a cross-sectional profile of a
template pattern and a yield of self-assembly (the concentration
of particle dispersion: wt%)
Relation between
concentration of particle dispersion and a yield of
self-assembly.

10. Capillary force

11. Template transfer process
SiO2/Si substrate with assembled particles
Uncured PDMS was poured onto the template
(base compound : curing agent = 10:1)
(3) Degassing for 30 min
(4) Curing PDMS (60 ℃ for 4 hr)
(5) Peel off PDMS

12. Au self-assemble on the template
Transferred pattern on the PDMS
(> 90% successful)

13. LSPR principle
Noble metal nanoparticles exhibit a strong UV-vis absorption band that is not present in the spectrum of the bulk metal.
This absorption band results when the incident photon frequency is resonant with the collective oscillation of the conduction electrons and is known as the localized surface plasmon resonance (LSPR).
E(λ) = extinction (viz., sum of absorption and scattering)
NA = area density of nanoparticles
a = radius of the metallic nanosphere
em = dielectric constant of the medium surrounding the metallic nanosphere
λ = wavelength of the absorbing radiation
εi = imaginary portion of the metallic nanoparticle's dielectric function
εr = real portion of the metallic nanoparticle's dielectric function
χ = 2 for a sphere (aspect ratio of the nanoparticle)

14. LSPR characteristics These mechanisms are:
resonant Rayleigh scattering from nanoparticle labels in a manner analogous to fluorescent dye labels
nanoparticle aggregation
charge-transfer interactions at nanoparticle surfaces
local refractive index changes
This approach has many advantages including:
a simple fabrication technique that can be performed in most labs
real-time biomolecule detection using UV-vis spectroscopy
a chip-based design that allows for multiplexed analysis

15. LSPR applications Sensor adsorption of small molecules
ligand-receptor binding
protein adsorption on self-assembled monolayers
antibody-antigen binding
DNA and RNA hybridization
protein-DNA interactions

16. LSPR scattering spectrum
Dot pattern
aperture
Schematic of dark-field microscope
line pattern

17. Dark-field microscope
Diagram illustrating the light path through a dark field microscope.
Light enters the microscope for illumination of the sample.
A specially sized disc, the patch stop (see figure) blocks some light from the light source, leaving an outer ring of illumination.
The condenser lens focuses the light towards the sample.
The light enters the sample. Most is directly transmitted, while some is scattered from the sample.
The scattered light enters the objective lens, while the directly transmitted light simply misses the lens and is not collected due to a direct illumination block (see figure).
Only the scattered light goes on to produce the image, while the directly transmitted light is omitted.

18. Scattering spectrums of line patterns w/o polarization
line pattern w/o polarization
Vacuum
air
methanol
water
ethanol
hexane
toluene
xylene
Refractive
index
1.0
1.0008
1.329
1.330
1.36
1.3749
1.4963
1.498

19. Spectrum peak vs. refractive index
Polarizing cube beamsplitter
p-polarized light
s-polarized light
Non-polarized light
non-polarized light
p-polarized light
s-polarized light

20. Conclusions
Self-assembly nanoparticle pattern formation method can be realized more than 90% onto 200 x 200 dots.
Dot and line patterns of gold nanoparticles in diameter of 60 nm were transferred on a flexible PDMS substrate.
LSPR sensitivity will be possible by controlling patterns of the assembled nanoparticles.
In the future, it is expected that this method will realize novel MEMS/NEMS devices with nanoparticles patterns on various 3D microstructures made of various materials via a carrier substrate.