A novel biosensor utilizing an interference of light reflected at the interfaces of a multilayer structure is proposed. This biosensor detects analytes by monitoring the changes in reflection intensity due to their adsorption to the sensor surface, on which functional biomolecules are immobilized to specifically bind to the analytes. The proposed biosensing instrument is based on a commercial digital versatile disc (DVD) system, which allows the instrument to be small and inexpensive. For the preliminary examination, SiO 2 thin films with a well-defined thickness were deposited on the sensor surface. The reflection intensity varied almost linearly depending on the thickness of the SiO 2 films in a thickness range of 2 -10 nm. Subsequently, it was demonstrated that biotin-streptavidin binding events were clearly detectable on a rotating disc substrate at a constant linear velocity of 4.0 m/s. We named this interference-based biosensor BioDVD, which is expected to be useful for highthroughput multi-analyte bioassays.
We provide a fabrication method for silver nano-particles with a uniform particle size using
vacuum deposition. The size uniformity was controlled by a small amount of
neodymium–copper (Nd–Cu) as a co-sputtered material. Particles with a size of
20 ± 7 nm dispersed
in a SiO2
matrix have been obtained. The full width at half maximum of the plasmon resonance in
the optical spectrum by the silver–neodymium–copper (Ag–Nd–Cu) nano-particles was
only half of the size compared with the spectral width of a pure Ag nano-particle
system. The effect is attributed to an increased uniformity in the particle size.
The recording and retrieval characteristics of super-resolution near-field structure disks have been evaluated before and after the fabrication of a Ag-nanostructured film on the top dielectric layer, using a 405nm wavelength laser and a 0.65 numerical aperture lens system. The carrier-to-noise ratio for 100nm mark signals is significantly improved by applying the Ag-nanostructured film. The underlying mechanism for the enhancement depends on the top dielectric layer thickness. A simulation based on Mie theory shows good agreement with the measured reflectance spectrum for the Ag-nanostructured film.
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