Post on 23-Feb-2016
description
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
AbstractPattern 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 assemblyMechanism 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
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.