Publications by authors named "Hyeonggon Kang"

12 Publications

  • Page 1 of 1

Lipoic Acid Decorated Gold Nanoparticles and Their Application in the Detection of Lead Ions.

J Nanomed Nanotechnol 2019 12;10(6). Epub 2019 Dec 12.

Center for Nanotechnology, Department of Natural Sciences, Coppin State University, 2500 W. North Ave, Baltimore, MD, USA.

A simple colorimetric method has been developed for the detection of lead (Pb) in water samples using lipoic acid-functionalized gold nanoparticles. The lipoic acid-functionalized gold nanoparticles are induced to aggregate in the presence of the Pb which results in a change in the color of the functionalized gold nanoparticles. The change in color and the amount of Pb producing the change could be monitored via UV-visible spectrophotometry. A good correlation coefficient of 0.9927 was obtained for the calibration curve of the colorimetric method. The method was applied in the determination of Pb in water samples and the results compared to that of measurement carried out with Atomic Absorption Spectroscopy.
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http://dx.doi.org/10.35248/2157-7439.19.10.539DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6986728PMC
December 2019

Terahertz Reflectometry Imaging of Carbon Nanomaterials for Biological Application.

J Nanomed Nanotechnol 2019 26;10(4). Epub 2019 Aug 26.

Department of Natural Sciences, Center for Nanotechnology, Coppin State University, 2500 W. North Ave, Baltimore, MD, USA.

The multiwalled carbon nanotubes has a myriad of applications due to its unique electrical and mechanical properties. The biomedical application of multiwalled carbon nanotubes that have been reported include drug delivery, medical imaging, gene delivery, tissue regeneration, and diagnostics. Proper characterization is required to enhance the potential application of the multiwalled carbon nanotubes. Terahertz technology is a relatively unfamiliar spectrometric technique that show promise in efficiently characterizing multiwalled carbon nanotubes. In this paper, terahertz imaging was used to characterize multiwalled carbon nanotube in comparison with other characterization techniques, including transmission electron microscopy and field emission scanning electron microscopy. The average diameter of the carbon nanotubes from the reconstructed terahertz images was 48.54 nm, while the average length of a fiber was found to be approximately 1.2 μm. The multiwalled carbon nanotubes were additionally characterized by FTIR, Raman spectroscopy, and Energy-dispersive X-ray spectroscopy.
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http://dx.doi.org/10.35248/2157-7439.19.10.535DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6738974PMC
August 2019

Dendrimer-based Nanoparticle for Dye Sensitized Solar Cells with Improved Efficiency.

J Nanomed Nanotechnol 2018 13;9(2). Epub 2018 Apr 13.

Department of Neurosurgery, Cellular and Molecular Imaging Laboratory, Henry Ford Hospital, Detroit, MI, USA.

Dye sensitized solar cells were fabricated with DyLight680 (DL680) dye and its corresponding europium conjugated dendrimer, DL680-Eu-G5PAMAM, to study the effect of europium on the current and voltage characteristics of the DL680 dye sensitized solar cell. The dye samples were characterized by using Absorption Spectroscopy, Emission Spectroscopy, Fluorescence lifetime and Fourier Transform Infrared measurements. Transmission electron microscopy imaging was carried out on the DL680-Eu-G5PAMAM dye and DL680-Eu-G5PAMAM dye sensitized titanium dioxide nanoparticles to analyze the size of the dye molecules and examine the interaction of the dye with titanium dioxide nanoparticles. The DL680-Eu-G5PAMAM dye sensitized solar cells demonstrated an enhanced solar-to-electric energy conversion of 0.32% under full light illumination (100 mWcm, AM 1.5 Global) in comparison with that of DL680 dye sensitized cells which recorded an average solar-to-electric energy conversion of only 0.19%. The improvement of the efficiency could be due to the presence of the europium that enhances the propensity of dye to absorb sunlight.
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http://dx.doi.org/10.4172/2157-7439.1000496DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5976458PMC
April 2018

Nondestructive shape process monitoring of three-dimensional high aspect ratio targets using through-focus scanning optical microscopy.

Meas Sci Technol 2018 12 6;29(12). Epub 2018 Nov 6.

SUNY Poly SEMATECH, Albany, NY, 12203, USA.

Low-cost, high-throughput and nondestructive metrology of truly three-dimensional (3-D) targets for process control/monitoring is a critically needed enabling technology for high-volume manufacturing (HVM) of nano/micro technologies in multi-disciplinary areas. In particular, a survey of the typically used metrology tools indicates the lack of a tool that truly satisfies the HVM metrology needs of 3-D targets, such as high aspect ratio (HAR) targets. Using HAR targets here we demonstrate that through-focus scanning optical microscopy (TSOM) is a strong contender to fill the gap for 3-D shape metrology. Differential TSOM (D-TSOM) images are extremely sensitive to small and/or dissimilar types of 3-D shape variations. Based on this here we propose a TSOM method that involves creating a database of cross-sectional profiles of the HAR targets along with their respective D-TSOM signals. Using the database, we present a simple-to-use, low-cost, high-throughput and nondestructive process-monitoring method suitable for HVM of truly 3-D targets, which also does not require optical simulations, making its use straightforward and automatable. Even though HAR targets are used for this demonstration, the similar process can be applied to any truly 3-D targets with dimensions ranging from micro-scale to nano-scale. The TSOM method couples the advantage of analyzing truly isolated targets with the ability to simultaneously analyze many targets present in the large field-of-view of a conventional optical microscope.
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http://dx.doi.org/10.1088/1361-6501/aae4c2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6512994PMC
December 2018

Fabrication, Optimization and Characterization of Natural Dye Sensitized Solar Cell.

Sci Rep 2017 01 27;7:41470. Epub 2017 Jan 27.

Center for Nanotechnology, Department of Natural Sciences, Coppin State University, 2500 W. North Ave, Baltimore, MD, USA.

The dyes extracted from pomegranate and berry fruits were successfully used in the fabrication of natural dye sensitized solar cells (NDSSC). The morphology, porosity, surface roughness, thickness, absorption and emission characteristics of the pomegranate dye sensitized photo-anode were studied using various analytical techniques including FESEM, EDS, TEM, AFM, FTIR, Raman, Fluorescence and Absorption Spectroscopy. Pomegranate dye extract has been shown to contain anthocyanin which is an excellent light harvesting pigment needed for the generation of charge carriers for the production of electricity. The solar cell's photovoltic performance in terms of efficiency, voltage, and current was tested with a standard illumination of air-mass 1.5 global (AM 1.5 G) having an irradiance of 100 mW/cm. After optimization of the photo-anode and counter electrode, a photoelectric conversion efficiency (η) of 2%, an open-circuit voltage (Voc) of 0.39 mV, and a short-circuit current density (Isc) of 12.2 mA/cm were obtained. Impedance determination showed a relatively low charge-transfer resistance (17.44 Ω) and a long lifetime, signifying a reduction in recombination losses. The relatively enhanced efficiency is attributable in part to the use of a highly concentrated pomegranate dye, graphite counter electrode and TiCl treatment of the photo-anode.
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http://dx.doi.org/10.1038/srep41470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5270247PMC
January 2017

Parameter optimization for through-focus scanning optical microscopy.

Opt Express 2016 Jun;24(13):14915-24

It is important to economically and non-destructively analyze three-dimensional (3-D) shapes of nanometer to micrometer scale objects with sub-nanometer measurement resolution for emerging high-volume nanomanufacturing, especially for process control. High-throughput through-focus scanning optical microscopy (TSOM) demonstrates promise for such applications. TSOM uses a conventional optical microscope for 3-D shape metrology by making use of the complete set of through-focus, four-dimensional optical data. However, a systematic study showing the effect of various parameters on the TSOM method is lacking. Here we present the optimization of the basic parameters such as illumination numerical aperture (NA), collection NA, focus step height, digital camera pixel size, illumination polarization, and illumination wavelength to achieve peak performance of the TSOM method.
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http://dx.doi.org/10.1364/OE.24.014915DOI Listing
June 2016

Multimodal optical studies of single and clustered colloidal quantum dots for the long-term optical property evaluation of quantum dot-based molecular imaging phantoms.

Biomed Opt Express 2012 Jun 9;3(6):1312-25. Epub 2012 May 9.

Understanding the optical properties of clustered quantum dots (QDs) is essential to the design of QD-based optical phantoms for molecular imaging. Single and clustered core/shell colloidal QDs of dimers, trimers, and tetramers are self-assembled, separated, and preferentially collected using electrospray differential mobility analysis (ES-DMA) with electrostatic deposition. Multimodal optical characterization and analysis of their dynamical photoluminescence (PL) properties enables the long-term evaluation of the physicochemical and optical properties of QDs in a single or a clustered state. A multimodal time-correlated spectroscopic confocal microscope capable of simultaneously measuring the time evolution of PL intensity fluctuation, PL lifetime, and emission spectra reveals the long-term dynamic optical properties of interacting QDs in individual dimeric clusters of QDs. This new method will benefit research into the quantitative interpretation of fluorescence intensity and lifetime results in QD-based molecular imaging techniques. The process of photooxidation leads to coupling of the QDs in a dimer, leading to unique optical properties when compared to an isolated QD. These results guide the design and evaluation of QD-based phantom materials for the validation of the PL measurements for quantitative molecular imaging of biological samples labeled with QD probes.
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http://dx.doi.org/10.1364/BOE.3.001312DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3370972PMC
June 2012

Quantitative scheme for full-field polarization rotating fluorescence microscopy using a liquid crystal variable retarder.

Rev Sci Instrum 2012 May;83(5):053705

Radiation and Biomolecular Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA.

We present a quantitative scheme for full-field polarization rotating fluorescence microscopy. A quarter-wave plate, in combination with a liquid crystal variable retarder, provides a tunable method to rotate polarization states of light prior to its being coupled into a fluorescence microscope. A calibration of the polarization properties of the incident light is performed in order to correct for elliptical polarization states. This calibration allows the response of the sample to linear polarization states of light to be recovered. Three known polarization states of light can be used to determine the average fluorescent dipole orientations in the presence of a spatially varying dc offset or background polarization-invariant fluorescence signal. To demonstrate the capabilities of this device, we measured a series of full-field fluorescence polarization images from fluorescent analogs incorporated in the lipid membrane of Burkitts lymphoma CA46 cells. The fluorescent lipid-like analogs used in this study are molecules that are labeled by either a DiI (1,1(')-Dioctadecyl 3,3,3('),3(')-Tetramethylindocarbocyanine) fluorophore in its head group or a Bodipy (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) molecule in its acyl chain. A spatially varying contrast in the normalized amplitude was observed on the cell surface, where the orientation of the DiI molecules is tangential to the cell membrane. The internally labeled cellular structures showed zero response to changes in linear polarization, and the net linear polarization amplitude for these regions was zero. This instrument provides a low cost calibrated method that may be coupled to existing fluorescence microscopes to perform investigations of cellular processes that involve a change in molecular orientations.
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http://dx.doi.org/10.1063/1.4717682DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3365914PMC
May 2012

Shell and ligand-dependent blinking of CdSe-based core/shell nanocrystals.

Phys Chem Chem Phys 2010 Aug 7;12(32):9312-9. Epub 2010 Jul 7.

Bio-Nanotechnology Center, Department of Chemistry, Pohang University of Science and Technology, San31 Hyoja-dong Nam-gu, Pohang, Kyungbuk 790-784, Korea.

Blinking of zinc blende CdSe-based core/shell nanocrystals is studied as a function of shell materials and surface ligands. CdSe/ZnS, CdSe/ZnSe/ZnS and CdSe/CdS/ZnS core/shell nanocrystals are prepared by colloidal synthesis and six monolayers of larger bandgap shell materials are grown over the CdSe core. Organic-soluble nanocrystals covered with stearate are made water-soluble by ligand exchange with 3-mercaptopropionic acid. The light-emitting states of nanocrystals are characterized by absorption and emission spectroscopy as well as photoluminescence lifetime measurements in solution. The blinking time trace is recorded for single nanocrystals on a glass coverslip. Both on- and off-time distributions are fitted to the power law. The power-law exponents vary, depending on shell materials and surface ligands. The off-time exponents for organic and water-soluble nanocrystals are measured in the range of 1.36-1.55 and 1.25-1.37, respectively, while their on-time exponents are spread in the range of 1.53-1.86 and 1.85-2.17, respectively. Water-soluble surface passivation with thiolate prolongs the dark period regardless of shell materials and core/shell structures. Of the core/shell structures, CdSe/CdS/ZnS exhibits the longest bright state. The on/off-time exponents are inversely correlated, although the successive on/off events are not individually correlated. A two competing charge-tunneling model is presented to describe the variation of on- and off-time exponents with shell materials and surface ligands.
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http://dx.doi.org/10.1039/b924917fDOI Listing
August 2010

Multimodal, nanoscale, hyperspectral imaging demonstrated on heterostructures of quantum dots and DNA-wrapped single-wall carbon nanotubes.

ACS Nano 2009 Nov;3(11):3769-75

Optical Technology Division, Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.

A multimodality imaging technique integrating atomic force, polarized Raman, and fluorescence lifetime microscopies, together with 2D autocorrelation image analysis is applied to the study of a mesoscopic heterostructure of nanoscale materials. This approach enables simultaneous measurement of fluorescence emission and Raman shifts from a quantum dot (QD)-single-wall carbon nanotube (SWCNT) complex. Nanoscale physical and optoelectronic characteristics are observed including local QD concentrations, orientation-dependent polarization anisotropy of the SWCNT Raman intensities, and charge transfer from photoexcited QDs to covalently conjugated SWCNTs. Our measurement approach bridges the properties observed in bulk and single nanotube studies. This methodology provides fundamental understanding of the charge and energy transfer between nanoscale materials in an assembly.
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http://dx.doi.org/10.1021/nn901075jDOI Listing
November 2009

Quantitative characterization of quantum dot-labeled lambda phage for Escherichia coli detection.

Biotechnol Bioeng 2009 Dec;104(6):1059-67

National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.

We characterize CdSe/ZnS quantum dot (QD) binding to genetically modified bacteriophage as a model for bacterial detection. Interactions among QDs, lambda (lambda) phage, and Escherichia coli are examined by several cross-validated methods. Flow and image-based cytometry clarify fluorescent labeling of bacteria, with image-based cytometry additionally reporting the number of decorated phage bound to cells. Transmission electron microscopy, image-based cytometry, and electrospray differential mobility analysis allow quantization of QDs attached to each phage (4-17 QDs) and show that lambda phage used in this study exhibits enhanced QD binding to the capsid by nearly a factor of four compared to bacteriophage T7. Additionally, the characterization methodology presented can be applied to the quantitative characterization of other fluorescent nanocrystal-biological conjugates.
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http://dx.doi.org/10.1002/bit.22488DOI Listing
December 2009

Water-soluble DNA-wrapped single-walled carbon-nanotube/quantum-dot complexes.

Small 2009 Oct;5(19):2149-55

Materials and Construction Research Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA.

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http://dx.doi.org/10.1002/smll.200801932DOI Listing
October 2009