Surface plasmon resonance (SPR) biosensors based on attenuated total reflection (ATR) have been widely used in biochemistry and genetic engineering, because it is a sensitive and label-free method. The dimension of the sensing probe is millimeters or more, so that the required amount of a sample solution is more than 100 μL even if a micro chamber is used. For multifunctional biosensing applications, therefore, a small biosensing platform is needed. We employed localized surface plasmons (LSPs) in gold nanostructures, instead of the conventional ATR-based SPR, to realize such small sensing probes. A few works on biosensing developed in our research group will be shown in this paper. One is a fabrication method of gold nanoparticles by annealing of thin gold film less than 10 nm thick. The optimized condition for producing nanoparticles for biosensing applications is discussed. The other is a sensitive optical fiber biosensor based on LSPs in gold nanoparticles. This optical fiber biosensor has advantages: easy handling and remote sensing. These merits come from the fact that the sensor probe is formed at the endface of a standard multimode optical fiber whose core diameter is 50 μm. Instead of such a small probe area, it has similar sensitivity to that of the ATR-based SPR sensors. This optical fiber biosensor enables us to perform biosensing with a sample solution of less than 100 nL. Finally we show biosensing based on nonlinear optics. Second-harmonic generation is one of the secondorder nonlinear optical phenomena and is a surface sensitive phenomenon. Here we show that it provides us a highly sensitive way for biosensing.

Date Published: 28 September 2007
PDF: 8 pages
Proc. SPIE 6642, Plasmonics: Nanoimaging, Nanofabrication, and Their Applications III, 66420J (28 September 2007); doi: 10.1117/12.730827

Published in SPIE Proceedings Vol. 6642:
Plasmonics: Nanoimaging, Nanofabrication, and Their Applications III
Satoshi Kawata; Vladimir M. Shalaev; Din-Ping Tsai, Editor(s)