| Abstract
| - We present in this paper that porous silicon can be used as a large surface area matrix as well asthe transducer of biomolecular interactions. We report the fabrication of heavily doped p-type porous siliconwith pore diameters that can be tuned, depending on the etching condition, from approximately 5 to 1200 nm.The structure and porosity of the matrixes were characterized by scanning force microscopy (SFM) and scanningelectron microscopy (SEM), Brunnauer−Emmett−Teller nitrogen adsorption isotherms, and reflectanceinterference spectroscopy. The thin porous silicon layers are transparent to the visible region of the reflectancespectra due to their high porosity (80−90%) and are smooth enough to produce Fabry−Perot fringe patternsupon white light illumination. Porous silicon matrixes were modified by ozone oxidation, functionalized inthe presence of (2-pyridyldithiopropionamidobutyl)dimethylmethoxysilane, reduced to unmask the sulfhydrylfunctionalities, and coupled to biotin through a disulfide-bond-forming reaction. Such functionalized matrixesdisplay considerable stability against oxidation and corrosion in aqueous media and were used to evaluate theutility of porous silicon in biosensing. The streptavidin−biotin interactions on the surface of porous siliconcould be monitored by the changes in the effective optical thickness calculated from the observed shifts in theFabry−Perot fringe pattern caused by the change in the refractive index of the medium upon protein−ligandbinding. Porous silicon thus combines the properties of a mechanically and chemically stable high surfacearea matrix with the function of an optical transducer and as such may find utility in the fabrication of biosensordevices.
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