다공성 실리콘의 센싱 및 약물전달 응용.

Abstract

Ⅰ. Investigation of Optical Properties for Thermal Oxidized Porous Silicon Luminescent porous silicon samples were prepared by an electrochemical etching of n-type silicon (phosphorous doped, <100> orientation) of resistivity between 1-10 Ω/㎝. The etching solution was prepared by adding an equal volume of pure ethanol (Fisher Scientific) to an aqueous solution of HF (48% by weight; Fisher Scientific). The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Etching was carried out as a two-electrode galvanostatic procedure at an anodic current density of 50 mA/㎠ for 15 min. The porosity of the sample was about 80%. After formation of porous silicon, the samples were thermally oxidized at 100℃, 200℃, 300℃, and 400℃, respectively. The growth rate of SiO₂ layer on porous silicon was investigated using FT-IR instrument. Ⅱ. Porous Silicon Chip as a Dual Transducer Novel porous silicon chip exhibiting dual optical properties, both Fabry-Perot fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type silicon wafer (boron-doped, <100> orientation, resistivity 1～10Ω). The etching solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF (48% by weight). The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Etching was carried out as a two-electrode galvanostatic procedure at an anodic current. The surface of porous silicon was characterized by FTIR instrument. The porosity of samples was about 80%. Three different types of porous silicon, fresh porous silicon (Si-H terminated), oxidized porous silicon (Si-OH terminated), and surface-derivatized porous silicon (Si-R terminated) were prepared by the thermal oxidation and hydrosilylation. Then the samples were exposed to the vapor of various organics, such as methanol, ethanol, acetone, hexane, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic vapors. These surface-modified samples showed unique responding in both reflectivity and photoluminescence with various organic vapors. While polar molecules exhibit greater quenching photoluminescence, molecules having higher vapor pressure show greater red shift for reflectivity. Ⅲ. 1-D Photonic Crystals of DBR PSi/Polystyrene Composite for Drug Delivery Applications Free-standing distributed Bragg reflectors (DBR) porous silicon films are treated with polystyrene to produce flexible, stable composite materials in which the porous silicon matrix is covered with caffeine-impregnated polystyrene. Optical characteristics of DBR PSi/caffeine-impregnated polystyrene Composite retain their photonic feature for 3 days in pH 7 aqueous buffer solution. The appearance of caffeine and change of DBR peak were simultaneously measured by UV-vis spectrometer and Ocean Optics 2000 spectrometer. DBR PSi/caffeine-impregnated polystyrene composite releases caffeine 3 days in pH 7 aqueous buffer solution. Free-standing DBR film exhibits its photonic peak at 520 nm, but the photonic feature of composite films shifts to red by 35 nm. The intensity of photonic peak of composite is decreased exponentially as caffeine releases from the composite films. The blue shift of photonic peak has been also observed during caffeine release process, which indicates that the refractive index of composite decreases due to the release of drug from composite. The release quantity of caffeine exhibits a linear relationship with release time on log scale.