- Seminar [12/19] Surface Plasmon Resonance in Metallic Nano-structures: Sensing, Optofluidics and Optoelectronics
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Time and Date : 13:00 ~ 14:00 Thursday 12/19/2019
Place : C716, Engineering Building #3
Title : Surface Plasmon Resonance in Metallic Nano-structures: Sensing, Optofluidics and Optoelectronics
Surface plasmons have been widely studied in many branches of physical sciences because of their unique properties associated with electromagnetic radiation-induced free electron movements. Surface plasmon resonance (SPR), in particular, which is well-known for the generation of highly localized energy intensity in the nanoscale, has been investigated for various applications including sensing and nanophotonics.
SPR biosensors typically measures the shifts in resonance, which may take the form of intensity dip, spectral absorption or optical phase jump, when target molecules are being captured and immobilized at the sensor surface. Among them, the SPR phase has been shown to be most sensitive for detecting target molecules. Various interferometer configurations have been reported to improve the resolution limit of SPR biosensors. Amongst them the spectral-phase interferometer has been shown to be most promising.
SPR absorption also results in strong ohmic heating. A focused laser beam may induce highly localized hotspot through plasmonic absorption in gold nano-islands. Temperature gradient-induced trapping, guided optofluidic flow and valving are readily achievable. By varying the incident power density, which in turn changes the temperature within the hot spot, one can readily perform a sequence of operations on living cells including trapping, cell lysis and DNA amplification. This approach opens the possibility of a performing genetic diagnosis from a small cluster of cells purely through laser irradiation.
Plasmonic localization also enhances the performance of gas sensors through a “catalytic” process by altering the carrier injection mechanism on the surface of the sensor material. This leads to the use of photon energy instead of conventional heating for gas sensing activation. We have demonstrated a room-temperature gas sensor scheme activated by plasmonic absorption in nano-sized metallic structures. By decorating gold nanoparticles (Au NPs) on the surface of ZnO NTPs through a physical evaporation process, we have incorporated localized surface plasmon resonance (LSPR) at the surface of the ZnO NTPs. The presence of LSPR has lowered the photon energy requirement for achieving light activation. In our experiments, the sensing response at 500 ppm ethanol has been improved from 5.5 to 62 (an enhancement of over 10 times). We also observed improved sensing performance for other common organic vapors such as formaldehyde, acetone and methanol.
Presenter: Prof. Aaron Ho-Pui Ho / Department of Biomedical Engineering, The Chinese University of Hong Kong
Host: Prof. Kim, Donghyun, Yonsei EEE