Presentation on theme: "T. Ozaki, K. Sugano, T. Tsuchiya, O. Tabata"— Presentation transcript:
1 GOLD NANOPARTICLE PATTERNING BY SELF-ASSEMBLY AND TRANSFER FOR LSPR BASED SENSING T. Ozaki, K. Sugano, T. Tsuchiya, O. TabataDepartment of Micro Engineering, Kyoto University, Kyoto, JAPANADVISER: Dr .CHENG-SHINE-LIUREPORTER: SRINIVASU V P & HSIEH,HSIN-YISTUDENT ID: &
2 OUTLINE Abstract Introduction Process overview Template assisted self assemblyResults and discussionTransfer of nanoparticlesLSPR characteristics of assembled Nanoparticle patternsConclusion
3 Abstract Pattern formation Dot and line pattern Assembled particle pattern transferLocalized Surface Plasmon Resonance (LSPR)
4 Introduction Characteristics of nanoparticles Conventional nanopatterning techniquesAdvantages of proposed method60-nm diameter gold nanoparticles
5 PROCESS OVERVIEW1) Self-assembly step2)Transfer step
6 Template assisted self assembly Mechanism of TASAAqueous particle dispersionCapillary force
7 Result and discussion Effect of cross sectional shape Relation between yield and concentrationThe 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 atemplate pattern and a yield of self-assembly (the concentrationof particle dispersion: wt%)Relation betweenconcentration of particle dispersion and a yield ofself-assembly.
11 Template transfer process SiO2/Si substrate with assembled particlesUncured 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 principleNoble 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 nanoparticlesa = radius of the metallic nanosphereem = dielectric constant of the medium surrounding the metallic nanosphereλ = wavelength of the absorbing radiationεi = imaginary portion of the metallic nanoparticle's dielectric functionεr = real portion of the metallic nanoparticle's dielectric functionχ = 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 labelsnanoparticle aggregationcharge-transfer interactions at nanoparticle surfaceslocal refractive index changesThis approach has many advantages including:a simple fabrication technique that can be performed in most labsreal-time biomolecule detection using UV-vis spectroscopya chip-based design that allows for multiplexed analysis
15 LSPR applications Sensor adsorption of small molecules ligand-receptor bindingprotein adsorption on self-assembled monolayersantibody-antigen bindingDNA and RNA hybridizationprotein-DNA interactions
16 LSPR scattering spectrum Dot patternapertureSchematic of dark-field microscopeline 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 polarizationVacuumairmethanolwaterethanolhexanetoluenexyleneRefractiveindex1.01.00081.3291.3301.361.37491.49631.498
19 Spectrum peak vs. refractive index Polarizing cube beamsplitterp-polarized lights-polarized lightNon-polarized lightnon-polarized lightp-polarized lights-polarized light
20 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.