GOLD NANOPARTICLE PATTERNINGBY SELF-ASSEMBLY AND TRANSFER

FOR LSPR BASED SENSINGT. Ozaki, K. Sugano, T. Tsuchiya, O. Tabata

Department of Micro Engineering, Kyoto University

, Kyoto, JAPAN

ADVISER: Dr .CHENG-SHINE-LIUREPORTER: SRINIVASU V P & HSIEH,HSIN-YI

STUDENT ID: 9733881 & 9735803

OUTLINEAbstractIntroductionProcess overviewTemplate assisted self assemblyResults and discussionTransfer of nanoparticlesLSPR characteristics of assembled

Nanoparticle patternsConclusion

Abstract

Pattern formation

Dot and line pattern

Assembled particle pattern transfer

Localized Surface Plasmon Resonance (LSPR)

Introduction

Characteristics of nanoparticles

Conventional nanopatterning techniques

Advantages of proposed method

60-nm diameter gold nanoparticles

PROCESS OVERVIEW1) Self-assembly step 2)Transfer step

Template assisted self assembly

Mechanism of TASA

Aqueous particle dispersion

Capillary force

Result and discussionEffect of cross sectional shapeRelation between yield and concentration

The self-assembly yield is defined as the ratio of the total dot-patterned area to the properly assembled area.

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

Relation between a cross-sectional profile of atemplate pattern and a yield of self-assembly (the concentrationof particle dispersion: 0.002 wt%)

Relation betweenconcentration of particle dispersion and a yield ofself-assembly.

Capillary force

Template transfer process

(1) SiO2/Si substrate with assembled particles

(2) 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

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

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)

LSPR characteristicsThese mechanisms are:

resonant Rayleigh scattering from nanoparticle labels in a manner analogous to fluorescent dye labels

nanoparticle aggregationcharge-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

LSPR applications

Sensoradsorption of small

molecules ligand-receptor bindingprotein adsorption on self-

assembled monolayersantibody-antigen bindingDNA and RNA

hybridizationprotein-DNA interactions

LSPR scattering spectrum

Schematic of dark-field microscope

Dot pattern

line pattern

aperture

Dark-field microscope

Scattering spectrums of line patterns 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

line pattern w/o polarization

Spectrum peak vs. refractive index

Polarizing cube beamsplitter

p-polarized light s-polarized light

Non-polarized light

p-polarized light s-polarized lightnon-polarized light

ConclusionsSelf-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.