Multi-Encoded Rugate Porous Silicon as Nerve Agents Sensors

Abstract

The nanostructured rugate porous silicons (PSi) containing multiple photonic band gaps have been generated by an electrochemical etching through applying a composite waveform summed three computer-generated pseudo-sinusoidal current waveforms. They exhibit three sharp photonic band gaps in the optical reflectivity spectrum, corresponding to the each of the sine components varied from 0.42, 0.36, and 0.30 Hz, with a spacing of 0.06 Hz between each sine component. The sensing experiments using multi-encoded rugate PSi for the detection of nerve agents such as triethyl phosphate (TEP), diethyl chlorophosphate (DCP), dimethyl methylphosphonate (DMMP), and diethyl ethylphosphonate (DEEP) have been achieved. Capillary condensation in the pores causes the reflectivity of rugate PSi to shift to longer wavelengths due to an increase in refractive indices of the porous medium.

Fabrication and Optical Characterization of Multi-Encoded Rugate Porous Silicon/Polymer Composite

“…The rugate PS prepared with a sine etching current profile possess a sinusoidally varying porosity gradient in the direction perpendicular to the plane of the filter. 18 To encode multiple rugate structures, three sine waves are summed together to create the composite waveform, which is used as an electrochemical etching current profile. 19 Therefore, multiple rugate PS might have a complex wave-formed porosity gradient rather than a simple porosity of cylindrical macro-pores in the direction perpendicular to the plane of the filter due to the sum of sine components.…”

“…16 Multi-encoded rugate filters were recently developed by applying a computer-generated pseudo-sinusoidal composite current-time waveform. 17 18 The refractive index * Author to whom correspondence should be addressed. varied sinusoidally in a photonic structure of rugatestructured PS.…”

Preparation and Characterization of Flexible Optical Composite Films Based on Bragg-Structured Interferometer

“…Since the discovery of porous silicon (PSi) [1] , it has been intensively investigated for a variety of applications such as chemical and biological sensors, medical diagnostics, and drug delivery [2][3][4][5][6][7][8][9][10][11][12][13][14] . The morphology and optical properties depend on surface orientation, doping level and type, temperature, the current density, and the composition of the etching solution [15][16][17][18][19][20][21][22][23] .…”

Fabrication and Characterization of Dodecyl-derivatized Silicon Nanowires for Preventing Aggregation

“…[8][9][10][11][12][13][14] Due to material abundance and nontoxicity, the silicon-based materials are highly favored at a huge industrial infrastructure for low production/processing costs and high production yields. Bulk silicon does not emit visible light, because it is an indirect band gap material with a small exciton-binding energy (15 meV).…”