Analytical Sciences

Backward-scattering-based Localized Surface Plasmon Resonance Sensors with Gold Nanospheres and Nanoshells

Tokuhisa KAWAWAKI, Naoaki SHINJO, and Tetsu TATSUMA

Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan

Localized surface plasmon resonance (LSPR) sensors based on plasmonic nanoparticles are sensitive to changes in local refractive index, so that they are used for affinity-based chemical sensing and biosensing. Conventional LSPR sensors are generally based on transmission of light through the sensor and a sample solution, which could be colored or turbid. In this study, we develop backward-scattering-based LSPR sensors that can be applied to colored or turbid sample solutions. Au nanospheres (100 nm diameter) and Au nanoshells (25 nm thick) with SiO₂ cores (80 nm diameter) are used as plasmonic nanoparticles and immobilized on a glass substrate. The refractive index sensitivities of the Au nanospheres and nanoshells are 128 and 278 nm RIU⁻¹, respectively, which are in good agreement with simulated values and the values for conventional transmission-based LSPR sensors. The Au nanoshells require a lower amount of Au for the same scattering intensity in comparison with the Au nanospheres. The backward-scattering-based LSPR sensing is possible with the Au nanospheres and nanoshells even in coffee as a colored and turbid sample.

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