PROCEEDINGS ARTICLE | October 10, 2012
Proc. SPIE. 8460, Biosensing and Nanomedicine V
KEYWORDS: Refractive index, Biosensing, Spectroscopy, Particles, Crystals, Silicon, Optical coatings, Reflectivity, Photonic crystals, Silicon photonics
In this paper we demonstrate the possibility of modifying porous silicon (PSi) particles with surface chemistry and
immobilizing a biopolymer, gelatin for the detection of protease enzymes in solution. A rugate filter, a one-dimensional
photonic crystal, is fabricated that exhibits a high-reflectivity optical resonance that is sensitive to small changes in the
refractive index. To immobilize gelatin in the pores of the particles, the hydrogen-terminated silicon surface was first
modified with an alkyne, 1,8-nonadiyne via hydrosilylation to protect the silicon surfaces from oxidation. This
modification allows for further functionality to be added such as the coupling of gelatin. Exposure of the gelatin
modified particles to the protease subtilisin in solution causes a change in the refractive index, resulting in a shift of the
resonance to shorter wavelengths, indicating cleavage of organic material within the pores. The ability to monitor the
spectroscopic properties of microparticles, and shifts in the optical signature due to changes in the refractive index of the
material within the pore space, is demonstrated.
