Bonghwan CHON - Academia.edu (original) (raw)
Papers by Bonghwan CHON
Semiconductor Science and Technology, Aug 13, 2008
International Journal of Molecular Sciences
The optical properties of indocyanine green (ICG) as a near-infrared (NIR) fluorescence dye depen... more The optical properties of indocyanine green (ICG) as a near-infrared (NIR) fluorescence dye depend on the nature of the solvent medium and the dye concentration. In the ICG absorption spectra of water, at high concentrations, there were absorption maxima at 700 nm, implying H-aggregates. With ICG dilution, the main absorption peak was at 780 nm, implying monomers. However, in ethanol, the absorption maximum was 780 nm, and the shapes of the absorption spectra were identical regardless of the ICG concentration, indicating that ICG in ethanol exists only as a monomer without H-aggregates. We found that emission was due to the monomer form and decreased with H-aggregate formation. In the fluorescence spectra, the 820 nm emission band was dominant at low concentrations, whereas at high concentrations, we found that the emission peaks were converted to 880 nm, suggesting a new form via the twisted intramolecular charge transfer (TICT) process of ICG. The NIR fluorescence intensity of ICG...
Analytical chemistry, 2021
Infrared (IR) absorption spectroscopy is a powerful tool that can quantify complex biomolecules a... more Infrared (IR) absorption spectroscopy is a powerful tool that can quantify complex biomolecules and their structural conformations. However, conventional approaches to protein analysis in aqueous solutions have been significantly challenged because the strong IR absorption of water overwhelms the limited dynamic range of the detection system and thus allows only a very short path length and a limited concentration sensitivity. Here, we demonstrate a solvent absorption compensation (SAC) approach that can improve the concentration sensitivity and extend the available path length by distinguishing the analyte signal over the full dynamic range at each wavelength. Absorption spectra without any postprocessing show good linearity from 100 to 0.1 mg/mL protein concentration, allowing a >100 times enhanced signal-to-noise ratio in the amide I band compared to the non-SAC results. We apply this method to in situ investigate the isothermal kinetics of insulin fibrillation at two clinical...
We examine multiphoton-produced optical signals waveguided through single ZnO nanorod (NR) using ... more We examine multiphoton-produced optical signals waveguided through single ZnO nanorod (NR) using a newly developed, scanning offset-emission hyperspectral microscopy (SOHM) technique. SOHM acquires spectrally indexed and spatially resolved intensity maps/spectra of waveguided light intensity, while excitation/emission collection positions and light polarization are scanned. Hence, the powerful measurement capabilities of SOHM enable quantitative analyses of the different ZnO NR waveguiding behaviors specific to the multiphoton-generated emissions as a function of measurement position, and the optical origin of the guided signal. We subsequently reveal the distinct waveguiding behaviors of single ZnO NRs pertaining to the variously originated signals and discuss particularly attractive ZnO NR properties in CARS waveguiding. In this talk, I will present the distinctive CARS waveguiding nature through single ZnO NR, exhibiting high position and polarization-dependence.
The Journal of Physical Chemistry B
The Journal of Physical Chemistry Letters
Journal of Raman Spectroscopy
Design and Quality for Biomedical Technologies IX, 2016
Scripta Materialia, 2005
Gallium-doped silicon nitride nanowires sheathed with amorphous silicon oxynitride have been prep... more Gallium-doped silicon nitride nanowires sheathed with amorphous silicon oxynitride have been prepared on silicon substrates using GaN as the source of Ga. Ga plays important roles not only in the formation of silicon nitride nanowires but also their oxidation, forming the sheath of silicon oxynitride. The as-grown nanowires are of significance in facilitating complementary metal-oxide semiconductor-based nanodevice manufacturing. The photoluminescence spectra of the nanowires at 10 K and 300 K are also investigated.
Semicond Sci Technol, 2008
We report on continuous wave and time-resolved photoluminescent characteristics of Mg x Zn 1−x O ... more We report on continuous wave and time-resolved photoluminescent characteristics of Mg x Zn 1−x O (0 x 0.18) alloy nanorods grown on Si substrates using catalyst-free metal-organic chemical vapor deposition. Low temperature time-integrated photoluminescence (PL) spectra of the alloy nanorods clearly exhibited a dominant PL peak of a single Mg x Zn 1−x O phase without showing any PL peak from ZnO. In addition, dominant PL peak positions of the alloy nanorods were blueshifted with increasing Mg content in the nanomaterials. Using temperature-dependent PL spectra and time-resolved PL spectra of Mg x Zn 1−x O nanorods, we discuss the composition fluctuations in Mg x Zn 1−x O (0 x 0.18) nanorods.
Journal of Luminescence, 2016
All-optical camera, converting X-rays into visible photons, is a promising strategy for high-perf... more All-optical camera, converting X-rays into visible photons, is a promising strategy for high-performance X-ray imaging detector requiring high detection efficiency and ultrafast detector response time. Zinc oxide is a suitable material for all-optical camera due to its fast radiative recombination lifetime in subnanosecond regime and its radiation hardness. ZnO nanostructures have been considered as proper building blocks for ultrafast detectors with spatial resolution in sub-micrometer scale. To achieve remarkable enhancement of luminescence efficiency n-type doping in ZnO has been employed. However, luminescence dynamics of doped ZnO nanostructures have not been thoroughly investigated whereas undoped ZnO nanostructures have been employed to study their luminescence dynamics. Here we report a study of luminescence dynamics of hydrogen doped ZnO nanowires obtained by hydrogen plasma treatment. Hydrogen doping in ZnO nanowires gives rise to significant increase in the near-band-edge emission of ZnO and decrease in averaged photoluminescence lifetime from 300 to 140 ps at 10 K. The effects of hydrogen doping on the luminescent characteristics of ZnO nanowires were changed by hydrogen doping process variables.
J Phys Chem B, 2006
Starting from a mixture of Zn and BiI3, we grew nanowires and nanoplates on an oxidized Si substr... more Starting from a mixture of Zn and BiI3, we grew nanowires and nanoplates on an oxidized Si substrate at relatively low temperatures of 250 and 300 degrees C, respectively. The ZnO nanowires had diameters of approximately 40 nm and grew along the [110] direction rather than the conventional [0001] direction. The nanoplates had thicknesses of approximately 40 nm and lateral dimensions of 3-4 microm. The growth of both the nanowires and nanoplates is dominated by the synergy of vapor-liquid-solid (VLS) and direction conducting. Analysis of photoluminescence spectra suggested that the nanoplates contain more oxygen vacancies and have higher surface-to-volume ratios than the nanowires. The present results clearly demonstrate that the shapes of ZnO nanostructures formed by using BiI3 can be controlled by varying the temperature in the range 250-300 degrees C.
Journal of biophotonics, Jan 16, 2015
A new optical scattering contrast-agent based on polymer-nanoparticle encapsulated silver nanopla... more A new optical scattering contrast-agent based on polymer-nanoparticle encapsulated silver nanoplates (PESNs) is presented. Silver nanoplates were chosen due to the flexibility of tuning their plasmon frequencies. The polymer coating preserves their physical and optical properties and confers other advantages such as controlled contrast agent delivery. Finite difference time domain (FDTD) simulations model the interaction of light with the nanoplates in different orientations in the cluster. Hyperspectral dark field microscopy (HYDFM) observes the scattering spectra of the PESNs. An unsupervised sequential maximum angle convex cone (SMACC) image analysis resolves spectral endmembers corresponding to different stacking orientations of the nanoplates. The orientation-dependent endmembers qualitatively agree with the FDTD results. For contrast enhancement, the uptake and spatial distribution of PESNs are demonstrated by an HYDFM study of single melanoma cells to result in an enhanced co...
Journal of biomedical optics, 2015
A hyperspectral image projector (HIP) based on liquid crystal on silicon spatial light modulators... more A hyperspectral image projector (HIP) based on liquid crystal on silicon spatial light modulators is explained and demonstrated to generate data cubes. The HIP-constructed data cubes are three-dimensional images of the spatial distribution of spectrally resolved abundances of intracellular light-absorbing oxyhemoglobin molecules in single erythrocytes. Spectrally and spatially resolved image data indistinguishable from the real scene may be used as standard data cubes, so-called digital phantoms, to calibrate image sensors and validate image analysis algorithms for their measurement quality, performance consistency, and interlaboratory comparisons for quantitative biomedical imaging applications.
The Journal of chemical physics, Jan 28, 2015
The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-... more The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O-D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O-D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O-D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O-D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quan...
Design and Performance Validation of Phantoms Used in Conjunction with Optical Measurement of Tissue VII, 2015
Physical Chemistry Chemical Physics, 2014
Experimental procedure in confocal single molecule fluorescence lifetime correlation spectroscopy... more Experimental procedure in confocal single molecule fluorescence lifetime correlation spectroscopy to determine the excitation power and molecular or particulate concentration under which the application of an unmodified model autocorrelation function is justified.
Semiconductor Science and Technology, Aug 13, 2008
International Journal of Molecular Sciences
The optical properties of indocyanine green (ICG) as a near-infrared (NIR) fluorescence dye depen... more The optical properties of indocyanine green (ICG) as a near-infrared (NIR) fluorescence dye depend on the nature of the solvent medium and the dye concentration. In the ICG absorption spectra of water, at high concentrations, there were absorption maxima at 700 nm, implying H-aggregates. With ICG dilution, the main absorption peak was at 780 nm, implying monomers. However, in ethanol, the absorption maximum was 780 nm, and the shapes of the absorption spectra were identical regardless of the ICG concentration, indicating that ICG in ethanol exists only as a monomer without H-aggregates. We found that emission was due to the monomer form and decreased with H-aggregate formation. In the fluorescence spectra, the 820 nm emission band was dominant at low concentrations, whereas at high concentrations, we found that the emission peaks were converted to 880 nm, suggesting a new form via the twisted intramolecular charge transfer (TICT) process of ICG. The NIR fluorescence intensity of ICG...
Analytical chemistry, 2021
Infrared (IR) absorption spectroscopy is a powerful tool that can quantify complex biomolecules a... more Infrared (IR) absorption spectroscopy is a powerful tool that can quantify complex biomolecules and their structural conformations. However, conventional approaches to protein analysis in aqueous solutions have been significantly challenged because the strong IR absorption of water overwhelms the limited dynamic range of the detection system and thus allows only a very short path length and a limited concentration sensitivity. Here, we demonstrate a solvent absorption compensation (SAC) approach that can improve the concentration sensitivity and extend the available path length by distinguishing the analyte signal over the full dynamic range at each wavelength. Absorption spectra without any postprocessing show good linearity from 100 to 0.1 mg/mL protein concentration, allowing a >100 times enhanced signal-to-noise ratio in the amide I band compared to the non-SAC results. We apply this method to in situ investigate the isothermal kinetics of insulin fibrillation at two clinical...
We examine multiphoton-produced optical signals waveguided through single ZnO nanorod (NR) using ... more We examine multiphoton-produced optical signals waveguided through single ZnO nanorod (NR) using a newly developed, scanning offset-emission hyperspectral microscopy (SOHM) technique. SOHM acquires spectrally indexed and spatially resolved intensity maps/spectra of waveguided light intensity, while excitation/emission collection positions and light polarization are scanned. Hence, the powerful measurement capabilities of SOHM enable quantitative analyses of the different ZnO NR waveguiding behaviors specific to the multiphoton-generated emissions as a function of measurement position, and the optical origin of the guided signal. We subsequently reveal the distinct waveguiding behaviors of single ZnO NRs pertaining to the variously originated signals and discuss particularly attractive ZnO NR properties in CARS waveguiding. In this talk, I will present the distinctive CARS waveguiding nature through single ZnO NR, exhibiting high position and polarization-dependence.
The Journal of Physical Chemistry B
The Journal of Physical Chemistry Letters
Journal of Raman Spectroscopy
Design and Quality for Biomedical Technologies IX, 2016
Scripta Materialia, 2005
Gallium-doped silicon nitride nanowires sheathed with amorphous silicon oxynitride have been prep... more Gallium-doped silicon nitride nanowires sheathed with amorphous silicon oxynitride have been prepared on silicon substrates using GaN as the source of Ga. Ga plays important roles not only in the formation of silicon nitride nanowires but also their oxidation, forming the sheath of silicon oxynitride. The as-grown nanowires are of significance in facilitating complementary metal-oxide semiconductor-based nanodevice manufacturing. The photoluminescence spectra of the nanowires at 10 K and 300 K are also investigated.
Semicond Sci Technol, 2008
We report on continuous wave and time-resolved photoluminescent characteristics of Mg x Zn 1−x O ... more We report on continuous wave and time-resolved photoluminescent characteristics of Mg x Zn 1−x O (0 x 0.18) alloy nanorods grown on Si substrates using catalyst-free metal-organic chemical vapor deposition. Low temperature time-integrated photoluminescence (PL) spectra of the alloy nanorods clearly exhibited a dominant PL peak of a single Mg x Zn 1−x O phase without showing any PL peak from ZnO. In addition, dominant PL peak positions of the alloy nanorods were blueshifted with increasing Mg content in the nanomaterials. Using temperature-dependent PL spectra and time-resolved PL spectra of Mg x Zn 1−x O nanorods, we discuss the composition fluctuations in Mg x Zn 1−x O (0 x 0.18) nanorods.
Journal of Luminescence, 2016
All-optical camera, converting X-rays into visible photons, is a promising strategy for high-perf... more All-optical camera, converting X-rays into visible photons, is a promising strategy for high-performance X-ray imaging detector requiring high detection efficiency and ultrafast detector response time. Zinc oxide is a suitable material for all-optical camera due to its fast radiative recombination lifetime in subnanosecond regime and its radiation hardness. ZnO nanostructures have been considered as proper building blocks for ultrafast detectors with spatial resolution in sub-micrometer scale. To achieve remarkable enhancement of luminescence efficiency n-type doping in ZnO has been employed. However, luminescence dynamics of doped ZnO nanostructures have not been thoroughly investigated whereas undoped ZnO nanostructures have been employed to study their luminescence dynamics. Here we report a study of luminescence dynamics of hydrogen doped ZnO nanowires obtained by hydrogen plasma treatment. Hydrogen doping in ZnO nanowires gives rise to significant increase in the near-band-edge emission of ZnO and decrease in averaged photoluminescence lifetime from 300 to 140 ps at 10 K. The effects of hydrogen doping on the luminescent characteristics of ZnO nanowires were changed by hydrogen doping process variables.
J Phys Chem B, 2006
Starting from a mixture of Zn and BiI3, we grew nanowires and nanoplates on an oxidized Si substr... more Starting from a mixture of Zn and BiI3, we grew nanowires and nanoplates on an oxidized Si substrate at relatively low temperatures of 250 and 300 degrees C, respectively. The ZnO nanowires had diameters of approximately 40 nm and grew along the [110] direction rather than the conventional [0001] direction. The nanoplates had thicknesses of approximately 40 nm and lateral dimensions of 3-4 microm. The growth of both the nanowires and nanoplates is dominated by the synergy of vapor-liquid-solid (VLS) and direction conducting. Analysis of photoluminescence spectra suggested that the nanoplates contain more oxygen vacancies and have higher surface-to-volume ratios than the nanowires. The present results clearly demonstrate that the shapes of ZnO nanostructures formed by using BiI3 can be controlled by varying the temperature in the range 250-300 degrees C.
Journal of biophotonics, Jan 16, 2015
A new optical scattering contrast-agent based on polymer-nanoparticle encapsulated silver nanopla... more A new optical scattering contrast-agent based on polymer-nanoparticle encapsulated silver nanoplates (PESNs) is presented. Silver nanoplates were chosen due to the flexibility of tuning their plasmon frequencies. The polymer coating preserves their physical and optical properties and confers other advantages such as controlled contrast agent delivery. Finite difference time domain (FDTD) simulations model the interaction of light with the nanoplates in different orientations in the cluster. Hyperspectral dark field microscopy (HYDFM) observes the scattering spectra of the PESNs. An unsupervised sequential maximum angle convex cone (SMACC) image analysis resolves spectral endmembers corresponding to different stacking orientations of the nanoplates. The orientation-dependent endmembers qualitatively agree with the FDTD results. For contrast enhancement, the uptake and spatial distribution of PESNs are demonstrated by an HYDFM study of single melanoma cells to result in an enhanced co...
Journal of biomedical optics, 2015
A hyperspectral image projector (HIP) based on liquid crystal on silicon spatial light modulators... more A hyperspectral image projector (HIP) based on liquid crystal on silicon spatial light modulators is explained and demonstrated to generate data cubes. The HIP-constructed data cubes are three-dimensional images of the spatial distribution of spectrally resolved abundances of intracellular light-absorbing oxyhemoglobin molecules in single erythrocytes. Spectrally and spatially resolved image data indistinguishable from the real scene may be used as standard data cubes, so-called digital phantoms, to calibrate image sensors and validate image analysis algorithms for their measurement quality, performance consistency, and interlaboratory comparisons for quantitative biomedical imaging applications.
The Journal of chemical physics, Jan 28, 2015
The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-... more The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O-D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O-D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O-D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O-D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quan...
Design and Performance Validation of Phantoms Used in Conjunction with Optical Measurement of Tissue VII, 2015
Physical Chemistry Chemical Physics, 2014
Experimental procedure in confocal single molecule fluorescence lifetime correlation spectroscopy... more Experimental procedure in confocal single molecule fluorescence lifetime correlation spectroscopy to determine the excitation power and molecular or particulate concentration under which the application of an unmodified model autocorrelation function is justified.