Porous silicon biosensors based on reflectometric ‎interference Fourier transform spectroscopy- theoretical ‎foundations and experimental results

Porous silicon (PSi) biosensor based on reflectometric interference Fourier transform spectroscopy ‎‎(RIFTS) has received a lot of attention due to its applicability as a label-free biosensor. In this ‎approach, light is illuminated on the surface of a PSi layer and the interference pattern of all reflected ‎beams from all interfaces is recorded. After exposing the PSi surface to bioanalyte, depending on ‎analyte's size, it absorbs on the surface of PSi layer or penetrates to the pores and absorbs on the wall of ‎the pores. This phenomenon causes variation in the refractive index of the interface of PSi/environment ‎or in the refractive index of the layer respectively. As a consequence, decrease in peak intensity or shift ‎in the peak position of fast Fourier transform of the interference pattern is observable, which can then ‎be used as a key parameter for biosensing applications. In this work, theoretical foundations of RIFTS ‎method were discussed. Then the experimental details of using this method for biosensing applications ‎on modified porous silicon were described. Finally, experimental data for diagnosis of Osteocalcin ‎protein, a piece of VKORC1 gen and Escherichia coli bacteria by RIFTS methods were illustrated.‎