Nanostructure and molecular interface for biosensing devices

In the recent literature, the development of optical biosensing devices has been focused on finding new methods and technologies to exploit the optical properties of noble metal nanostructure, especially localized surface plasmon resonance (LSPR)1-4. Theoretically, the LSPR is excited when the electromagnetic radiation of incident light interacts with the free electrons of the nanostructure, which results in the collective oscillations, leading to strong enhancements of the local electromagnetic fields surrounding the nanostructures 5-8. Therefore, the nanostructure surface plays an important role to inspect the surface plasmon band because it can alter the boundary conditions for the polarizability of noble metal, expressing in the changes of LSPR spectra9-11. Depending on the types of materials, sizes and shapes ofnanostructures, LSPR absorption peaks have various sensing capacity to the interfacial refractive index (RI) and biomolecular interactions12-15. The corresponding changes in both the peak intensity and wavelength are importantdetection signals for analytical and biological applications since the molecular interfaces are highly functionalized by chemical reactions. A number of nanostructure surfaces have been developed up to now 16-22. Some have the disadvantages, for instance, troublesome in fabrication of triangular nanoparticles by nanosphere lithography23or difficult controlling in nanoparticle diameter, surface layer of gold nanoparticles by chemical modifications 17..., thus limiting the flexibility in coupling with other techniques. Especially, the requirement Kretschmann configuration in total internal reflection system restricts to miniaturize these conventional LSPR devices into micro total analysis systems(µTAS) with a better selectivity, reagent economy and rapid detection 23-24.

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