1-D Photonic Crystals Based on Bragg Structure for Sensing and Drug Delivery Applications

Koh, Youngdae The Basic Science Institute Chosun University 2011 조선자연과학논문집 Vol.4 No.1

Free-standing multilayer distributed Bragg reflectors (DBR) porous silicon dielectric mirrors, prepared by electrochemical etching of crystalline silicon using square wave currents are treated with polymethylmethacrylate (PMMA) to produce flexible, stable composite materials in which the porous silicon matrix is covered with caffeine-impregnated PMMA. Optically encoded free-standing DBR PSi dielectric mirrors retain the optical reflectivity. Optical characteristics of free-standing DBR PSi dielectric mirrors are stable and robust for 24 hrs in a pH 12 aqueous buffer solution. The appearance of caffeine and change of DBR peak were simultaneously measured by UV-vis spectrometer and Ocean optics 2000 spectrometer, respectively.

1-D Photonic Crystals Based on Bragg Structure for Sensing and Drug Delivery Applications

Youngdae Koh 조선대학교 기초과학연구원 2011 조선자연과학논문집 Vol.4 No.1

Detection of Avidin Based on Rugate-structured Porous Silicon Interferometer

Youngdae Koh,Sung Jin Kim,Jaehyun Park,박철영,Sungdong Cho,우희권,Young Chun Ko*,Honglae Sohn* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.11

Biosensor based on rugate PSi interferometer for the detection of avidin has been described. Rugate PSi fabricated by applying a computer-generated pseudo-sinusoidal current waveform has been prepared for the application as a label-free biosensor based on porous silicon interferometer. The fabrication, optical characterization, and surface derivatization of a rugate PSi has been described. The method to fabricate biotin-derivatized rugate PSi has been investigated. The surface and cross sectional morphology of rugate PSi are obtained with SEM. FT-IR spectroscopy is used to characterize the oxidation and functionalization reaction of rugate PSi sample. Binding of the avidin into the biotin-derivatized rugate PSi induces a change in refractive index. A red-shift of reflectivity by 18 nm in the reflectivity spectrum is observed, when the biotin-modified rugate PSi was exposed to a flow of avidin.

1-D Photonic Crystals Based on Bragg Structure for Sensing and Drug Delivery Applications

Youngdae Koh 조선대학교 기초과학연구원 2011 조선자연과학논문집 Vol.3 No.4

Free-standing multilayer distributed Bragg reflectors (DBR) porous silicon dielectric mirrors, prepared by electrochemical etching of crystalline silicon using square wave currents are treated with polymethylmethacrylate (PMMA) to produce flexible, stable composite materials in which the porous silicon matrix is covered with caffeine-impregnated PMMA. Optically encoded free-standing DBR PSi dielectric mirrors retain the optical reflectivity. Optical characteristics of free-standing DBR PSi dielectric mirrors are stable and robust for 24 hrs in a pH 12 aqueous buffer solution. The appearance of caffeine and change of DBR peak were simultaneously measured by UV-vis spectrometer and Ocean optics 2000 spectrometer, respectively.

Porous Silicon Interferometric Sensors for the Detection of Nerve Agent Mimics Using Various Light Sources

장승현,Youngdae Koh,김지훈,Kyoungsun Jung,손홍래 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1

Various detection methods using nanostructured materials, such as distributed Bragg reflectors (DBRs), for sensing G-type nerve agent mimics have been developed. For DBRs, the versatile porous silicon (PSi) is prepared by electrochemical etching through applied square current waveform. The manufactured DBR exhibits unique optical properties providing the reflection of a specific wavelength in the optical reflectivity spectrum. The detection methods involve the shift of DBR in the reflectivity spectra under exposure to vapors of nerve agent mimics. Rapid detection has been achieved within 5 sec, in situ, and has been observed through the red-shift of the reflection peak caused by an increase in the refractive indices in PSi. Real-time detection for the nerve agent gases indicates that the measurement is reversible. The detection efficiency for nerve agent mimics is also increased when a light-emitting diode (LED, λem = 520 nm) or laser (λem = 530 nm) is used as an incident light source instead of a tungsten-halogen lamp. Various detection methods using nanostructured materials, such as distributed Bragg reflectors (DBRs), for sensing G-type nerve agent mimics have been developed. For DBRs, the versatile porous silicon (PSi) is prepared by electrochemical etching through applied square current waveform. The manufactured DBR exhibits unique optical properties providing the reflection of a specific wavelength in the optical reflectivity spectrum. The detection methods involve the shift of DBR in the reflectivity spectra under exposure to vapors of nerve agent mimics. Rapid detection has been achieved within 5 sec, in situ, and has been observed through the red-shift of the reflection peak caused by an increase in the refractive indices in PSi. Real-time detection for the nerve agent gases indicates that the measurement is reversible. The detection efficiency for nerve agent mimics is also increased when a light-emitting diode (LED, λem = 520 nm) or laser (λem = 530 nm) is used as an incident light source instead of a tungsten-halogen lamp.

Simply Modified Biosensor for the Detection of Human IgG Based on Protein AModified Porous Silicon Interferometer

Jaehyun Park,Youngdae Koh,손홍래,Young Chun Ko 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.7

A biosensor has been developed based on induced wavelength shifts in the Fabry-Perot fringes in the visible reflection spectrum of appropriately derivatized thin films of porous silicon semiconductors. Porous silicon (PSi) was generated by an electrochemical etching of silicon wafer using two electrode configurations in aqueous ethanolic HF solution. Porous silicon displayed Fabry-Perot fringe patterns whose reflection maxima varied spatially across the porous silicon. The sensor system studied consisted of a mono layer of porous silicon modified with Protein A. The system was probed with various fragments of an aqueous Human Immunoglobin G (Ig G) analyte. The sensor operated by measurement of the Fabry-Perot fringes in the white light reflection spectrum from the porous silicon layer. Molecular binding was detected as a shift in wavelength of these fringes.

Polygermole Nanoaggregate Chemical Sensor for TNT: Enhancement of Photoluminescence Efficiency by Aggregation-Induced Emission

Jang, Seunghyun,Koh, Youngdae,Woo, Hee-Gweon,Sohn, Honglae American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.2

<P>New photoluminescent and nanoscale polygermole nanoaggregates for the detection of 2,4,6-trinitrotoluene (TNT) were developed by using aggregation-induced emission property. Polygermole nanoaggregates displaying diameter of 40 nm exhibited that photoluminescence (PL) intensity of emission band was increased about 730% when the water fraction was increased to 90% by volume. Relative PL efficiency of polygermole nanoaggregates was exponentially increased to the percent of water fraction and particle diameter was dependent on solvent composition. Particle size of polygermole nanoaggregates was tuned by controlling the water fraction by volume. PL intensity of polygermole nanoaggregates was not changed over a month. This indicated that polygermole nanoaggregates showed neither further aggregation nor degradation. Detection of TNT was achieved from the measuring of quenching PL of polygermole nanoaggregates by adding the TNT A linear Stern-Volmer relationship was observed for the detection of TNT.</P>

Multi-Encoded Rugate Porous Silicon as Nerve Agents Sensors

Jang, Seunghyun,Kim, Jihoon,Koh, Youngdae,Ko, Young Chun,Woo, Hee-Gweon,Sohn, Honglae American Scientific Publishers 2007 Journal of Nanoscience and Nanotechnology Vol.7 No.11

<P>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.</P>

Photonic Polymer Replicas Containing CdSe Nanoparticles Based on Porous Silicon

김지훈,Seunghyun Jang,Youngdae Koh,김성진,고영춘,손홍래 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3

A photonic crystal containing a Bragg structure was prepared by applying a computer-generated periodic square current waveform and result in a mirror with high reflectivity in a specific narrow spectral region. This paper describes a method for the fabrication of photonic polymer replicas containing CdSe nanoparticles based on distributed Bragg reflector (DBR) porous silicon (PSi). Well-defined one-dimensional photonic polymethly methacrylate (PMMA) replicas containing CdSe nanoparticles showing a reflectivity at 571 nm and a photoluminescence at 560 nm were successfully obtained by removing the DBR PSi template from the PMMA composite film. XRD measurements indicated that the oxidized DBR PSi was completely removed from the composite films. The photonic polymer replicas exhibited a sharp resonance with a full width at half maximum (FWHM) of 20 nm in the reflectivity spectrum. The optical characteristics of the photonic polymer replicas indicated that the surface of the polymer film had the negative structure of DBR PSi. These replicas were stable in aqueous solutions for several days without any degradation. A photonic crystal containing a Bragg structure was prepared by applying a computer-generated periodic square current waveform and result in a mirror with high reflectivity in a specific narrow spectral region. This paper describes a method for the fabrication of photonic polymer replicas containing CdSe nanoparticles based on distributed Bragg reflector (DBR) porous silicon (PSi). Well-defined one-dimensional photonic polymethly methacrylate (PMMA) replicas containing CdSe nanoparticles showing a reflectivity at 571 nm and a photoluminescence at 560 nm were successfully obtained by removing the DBR PSi template from the PMMA composite film. XRD measurements indicated that the oxidized DBR PSi was completely removed from the composite films. The photonic polymer replicas exhibited a sharp resonance with a full width at half maximum (FWHM) of 20 nm in the reflectivity spectrum. The optical characteristics of the photonic polymer replicas indicated that the surface of the polymer film had the negative structure of DBR PSi. These replicas were stable in aqueous solutions for several days without any degradation.

Detection of G-Type Nerve Agent Simulants Based on a Double Reflection DBR Porous Silicon Interferometer

Seunghyun Jang,Honglae Sohn,Jihoon Kim,Youngdae Koh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2

Distributed Bragg reflector (DBR) porous silicon (PSi) chips with two reflection peaks were fabricated by electrochemical etching in an aqueous ethanolic HF solution and were used to detect of chemical nerve agent simulants. Dimethyl methylphosphonate (DMMP) is a simulant for G-type nerve agents. The manufactured DBR PSi chips exhibit two sharp photonic bands, 560 and 717 nm, with narrow full widths at half maximum (FWHM) of 15 and 20 nm, respectively. The detection method involved the shift of the DBR reflection peaks in the reflectivity spectra under exposure to vapors of the analyte. Rapid detection was achieved in few seconds in situ and the observed red shift of the DBR peaks resulted from an increase in the refractive indices in DBR PSi. When the DBR PSi chips were exposed to vapor of DMMP, the two reflection peaks from DBR PSi were red-shifted by 22 and 32 nm, respectively. Real-time detection for the stimulant indicated that the detection measurements were reversible. Detection of other analytes, such as triethyl phosphate (TEP) and diethyl ethylphosphonate (DEEP), has been also achieved. Distributed Bragg reflector (DBR) porous silicon (PSi) chips with two reflection peaks were fabricated by electrochemical etching in an aqueous ethanolic HF solution and were used to detect of chemical nerve agent simulants. Dimethyl methylphosphonate (DMMP) is a simulant for G-type nerve agents. The manufactured DBR PSi chips exhibit two sharp photonic bands, 560 and 717 nm, with narrow full widths at half maximum (FWHM) of 15 and 20 nm, respectively. The detection method involved the shift of the DBR reflection peaks in the reflectivity spectra under exposure to vapors of the analyte. Rapid detection was achieved in few seconds in situ and the observed red shift of the DBR peaks resulted from an increase in the refractive indices in DBR PSi. When the DBR PSi chips were exposed to vapor of DMMP, the two reflection peaks from DBR PSi were red-shifted by 22 and 32 nm, respectively. Real-time detection for the stimulant indicated that the detection measurements were reversible. Detection of other analytes, such as triethyl phosphate (TEP) and diethyl ethylphosphonate (DEEP), has been also achieved.