An ideal diagnostic device should be inexpensive, easy-to-use, rapid and reliable. Nanostructured porous silicon (PSi) satisfies these criterions including label-free optical detection and high throughput detection. Pore morphology (size, porosity) must be tailored for each specific application, and for immunosensing applications PSi morphology has been optimized for maximal pore infiltration of larger proteins as immuno gamma globlulin (IgG). Sensor degradation by high salt concentration induces a baseline drift. Different thermal oxidation procedures have been studied in order to obtain a stable sensor in the 3 hour incubation period of the immunoassay with negligible drift
A colorimetric resonant mesoporous silicon photonic crystal is used as a surface binding platform for biochemical
detection. The photonic crystal, when illuminated with white light at normal incidence, is designed to reflect a photonic
band gap (PBG) centered at a single wavelength. When molecules are attached to the internal surfaces of pores, the PBG
is shifted due to the change in refractive index of the porous silicon layers. The planar structure of the platform can be
easily integrated into a fluidic cell. We have optically verified the presence of proteins and chemicals as a colorimetric
shift in the reflectivity spectrum of mesoporous silicon photonic crystals and microcavities.
Optical properties of a planar array of composite Au/Co/Au magnetic plasmonic nanosandwiches of 60 and 110 nm in
diameter are studied using linear absorption and optical second harmonic generation (SHG) technique. Linear absorption
spectrum reveals a peak centered at about 2.1 eV, which is associated with the excitation of localized surface plasmon in
Au/Co/Au nanosandwiches. The nonlinear-optical experiments are performed using the fundamental radiation of YAG:
Nd3+ laser at 1064 nm, so that the SHG radiation corresponds to the resonant plasmon line. It is shown that in spite of
spatial inhomogeneity of such an ensemble, the SHG response in the nanosandwiches of the diameter 110 nm is
presumably polarized and specular, i.e. substantially coherent. At the same time, for nanosandwiches with the diameter
of 60 nm the SHG signal is observed in the form of the hyper-Rayleigh scattering. Plasmon-assisted effects in nonlinear-optical
response of nanosandwiches reveal themselves by different relative amplitude and phase of odd in magnetization
component of the SHG field as compared with those in plasmon-free continuous trilayer structure.
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