Microtech2010 2010

A comparative study on sensitivity for biomolecular detection between gold nanoparticles coated and uncoated gold thin film using spectroscopic ellipsometry

R.S. Moirangthem, Y.-C. Chang, S.-H. Hsu, P.-K. Wei
Research Center for Applied Sciences, TW

Keywords: spectroscopic ellipsometry, biosensor, surface plasmon resonance


We investigate the plasmonic responses of gold nanoparticles (AuNP) coated and uncoated on 30nm gold thin film with aqueous medium having different refractive index using SPR ellipsometry. (See Figure 1) The sensitivities in both cases have the same order of magnitude. However, the width of the surface plasmon resonance depth in case of AuNP coated gold thin film becomes much smaller than bare gold thin film. Thus a better figure of merit, thus better sensitivity, is obtained for the AuNP coated gold thin film. Hence, it can be used to study biomolecular interaction such as DNA hybridization. We monitor the induced changes in polarization state or phase of reflected light from the sample surface, which depend on surface properties of the sample, and use these changes as a function of the photon energy as a sensor signal and compare that with an efficient theoretical simulation. This kind of characterization technique is non-destructive, label free and it has high sensitivity and sub-nanometer thickness resolution. Furthermore, investigation can be made in aqueous medium.
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