• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.374-378
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• 1991

The electrochemical reduction behavior of Bilirubin (BR) in phosphate buffer (pH 7.8) solution was studied by DC polarography, differential pulse polarography, cyclic voltammetry and controlled potential coulometry. In DC polarogram, two reduction waves of BR were found. The half wave potentials of two reduction waves were -1.32 and -1.51 volts vs. Ag/AaCl respectively. The current type of 1st reduction wave was diffusion-controlled and the 2$^{nd}$ reduction wave was diffusion current containing a little kinetic current. The electrochemical reduction process of BR at each reduction step was all irreversible. The prewave appeared at lower concentration than 3.4 ${\times}$ 10$^{-4}$M, this prewave was identified as adsorption prewave. And the number of electron transfered in reduction steps, n$_{app}$ was two for the 1st reduction step and one for the 2$^{nd}$ reduction step.

• Carbon letters
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• v.21
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• pp.61-67
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• 2017

We report the use of carrot, a new and inexpensive biomaterial source, for preparing high quality carbon dots (CDs) instead of semi-conductive quantum dots for bioimaging application. The as-derived CDs possessing down and up-conversion photoluminescence features were obtained from carrot juice by commonly used hydrothermal treatment. The corresponding physiochemical and optical properties were investigated by electron microscopy, fluorescent spectrometry, and other spectroscopic methods. The surfaces of obtained CDs were highly covered with hydroxyl groups and nitrogen groups without further modification. The quantum yield of as-obtained CDs was as high as 5.16%. The cell viability of HaCaT cells against a purified CD aqueous solution was higher than 85% even at higher concentration ($700{\mu}g\;mL^{-1}$) after 24 h incubation. Finally, CD cultured cells exhibited distinguished blue, green, and red colors, respectively, during in vitro imaging when excited by three wavelength lasers under a confocal microscope. Offering excellent optical properties, biocompatibility, low cytotoxicity, and good cellular imaging capability, the carrot juice derived CDs are a promising candidate for biomedical applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.7
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• pp.455-461
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• 2018

Boron nitride (BN) nanofibers were fabricated using BN nanoparticles (70 nm) by electrospinning. Morphologies such as the diameter and density of the BN nanofibers are strongly influenced by the viscosity and dispersion state of the precursor solution. In this study, the precursor solution was prepared by ball milling BN nanoparticles and polyvinylpyrrolidone (PVP, Mw~1,300,000) in ethanol, which was electrospun and then calcined to produce BN fibers. High-quality BN nanofibers were well fabricated at a BN concentration of 15 wt% with their diameters in the range of 500 nm to 800 nm; the viscosity of the precursor solution was $400mPa{\cdot}S$. The calcination of the as-electrospun BN fibers seemed to be completed by holding them at $350^{\circ}C$ for 2 h considering the TGA data. The morphologies and phases of the BN fibers were investigated by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively; Fourier transform infrared (FT-IR) was also used for structure analysis.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3707-3711
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• 2011

Silver nanoparticles coated with silica can be obtained by the reduction of $AgNO_3$ with hydrazine in the presence of NaOH-stabilized, active silicic acid (polysilicic acid). The size of the silver nanoparticles and the silica shell thicknesses were affected by varying the hydrazine content, the active silicic acid content and the experimental method (e.g. hydrothermal method). Typically, silver nanoparticles sized around 40 nm were aggregated, connected by silica. The presence of peaks centered around 400 nm in UV-vis spectra corresponds to the surface plasmon resonance of silver nanoparticles. The size of the aggregated silver nanoparticles increased with increasing hydrazine concentration. Under hydrothermal conditions at $150^{\circ}C$ the formation of individual silica particles was observed and the sizes of the silver nanoparticles were reduced. The hydrothermal treatment of silver nanoparticles at $180^{\circ}C$ gives a well-defined Ag@$SiO_2$ core-shell in aggregated silica sol particles. The absorption band observed at around 412 nm were red-shifted with respect to the uncoated silver nanoparticles (${\lambda}_{max}$ = 399 nm) due to the larger refractive index of silica compared to that of water. The formation of silver nanoparticles coated with silica is confirmed by UV-visible absorption spectra, transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS) data.

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.108-114
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• 2007

The lyotropic behaviors to form the structure of distearoylphosphatidylcholine (DSPC)-based liquid crystal (LC) hydrated by only propylene glycol (PG) without water were examined by differential scanning calorimetry (DSC), X-ray diffractions (XRD), polarized microscope (PM) and transmission electron microscope (TEM). By increasing the amount of PG instead of water, it showed the phase transition to be gradually changed from anisotropic structures to other structures more close to isotropic ones and their appearance to be changed from solid-like states to liquid-like ones with more fluidity. Below 50% w/w PG, the mixtures of DSPC and PG resulted in no direct observation of LC structure through PM because they were very close to solid-states. From 55% w/w to 90% w/w of PG, the dense lamella crystalline structures were observed through PM, and their thickness and area decreased as the content of PG increased. Measured by DSC with heating process, the main phase transition from α -lamella phase to isotropic phase appeared from 52.89 °C to 47.41 °C to show linearly decreasing behaviors because PG affects the hydrophobic region of DSPC-based lamella phase. The repeating distance of the lamella phase and the interlayer distance between bilayers were calculated with XRDs and the average number of bilayers related to the thickness in LC structure was approximately estimated by combining with TEM results. The WAXS and DSC measurements showed that all of PG molecules contributed to swelling both the lipid layer in the edge region of lamella phase close to phosphate groups and the interlayer between bilayers below 90% w/w of PG. The phase and thermal behaviors were found to depend on the amount of PG used by means of dissolving DSPC as a phospholipid and rearranging its structure. Instead of water, the inducement of PG as a polar solvent in solid-lamella phase is discussed in terms of the swelling effect of PG for DSPC-based lamella membrane.

• Corrosion Science and Technology
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• v.19 no.1
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• pp.16-22
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• 2020

It is important to realize that benzoate was intercalated into hydrotalcite (HTC-Bz) by the co-precipitation method. In this case, acrylic coating with 0.5 wt% HTC-Bz was deposited on carbon steel using the spin coating method. Next, the HTC-Bz structure was characterized by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). In fact, an ultraviolet vision spectroscopy (UV-Vis) was used to determine the benzoate content in HTC-Bz, and the UV absorption ability of HTC-Bz. Using electrochemical techniques, water contact angle measurement, and thermal-gravimetric analysis, we compared the protective properties before and after QUV test, hydrophobicity and the thermal stability of acrylic coating containing HTC-Bz. The obtained results showed that HTC-Bz with a plate-like structure was successfully synthesized; benzoate was intercalated into the interlayer of hydrotalcite with a concentration of 28 wt%. Additionally, it was noted that HTC-Bz has an UV absorption peak at 225 nm. In conclusion, the addition of HTC-Bz enhanced the UV stability, hydrophobicity and the thermal stability of acrylic coating.

• Biomedical Science Letters
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• v.9 no.2
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• pp.85-91
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• 2003

Gentiana scabra var. buergeri (G. scabra) is a herb known to have therapeutic effect in infection diseases. We studied cellular activation and antitoxoplasmosis in macrophages after G. scabra stimulation. Macrophage activation was detected by nitrite production. Macrophages were treated with G. scabra extracted with water or methanol. Maximal nitrite production was detected in macrophages after stimulation of G. scabra extract 0.1 mg/ml. Maximal nitrite concentration was 23.22 0.003 uM/L in macrophages after water extract of G. scabra and was 24.07 1.41 uM/L after methanol extract of G. scabra. Effect of G. scabra in the phagocytic capacity of macrophages was monitored by using PI (percentage of macrophage infected by T gondii) method. The minimum PI (42.5 2.31) was detected in macrophages treated by water extract of G. scabra 0.1 mg/ml before infection of T gondii. We also examined toxoplasmastatic capacity of macrophage using FI (fold increase) method. The minimum FI (4.46 1.16) was shown in macrophages after water extract of G. scabra 0.1 mg/ml pretreatment before infection. Under electron microscope, proliferation of T gondii was inhibited by extract of G. scabra treatment in macrophages and the mitochondrion and lysosomal vacuoles within cells were increased. Taken together, G. scabra extract activates macrophages and induces toxopalsmastatic activity after T gondii infection. It is suggested that G. scabra may be used as a therapeutic drug against toxoplasmosis.

• Biomedical Science Letters
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• v.25 no.4
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• pp.348-356
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• 2019

This study evaluated the dermal cytotoxicity of sodium bromate (NaBrO₃) and the protective effect of Aster tataricus L. (AT) extract against NaBrO₃-induced cytotoxicity in the cultured NIH3T3 fibroblasts. For this study, it was done the antioxidative effects such as electron donating (ED) activity and lipid peroxidation (LP) activity as well as cell viability. NaBrO₃ significantly decreased cell viability in a dose-dependent manner and its XTT₅₀ value was measured at a concentration of 54.4 μM in these cultures. The cytotoxicity of NaBrO₃ was determined as highly-toxic by Borenfreund and Puerner's toxic criteria. The quercetin, antioxidant significantly increased cell viability against NaBrO₃-induced cytotoxicity. Regarding the protective effect of Aster tataricus (AT) L. extract on NaBrO₃-induced cytotoxicity, AT extract significantly increased the cell viability, the ED ability and the inhibitory ability of LP. From these findings, it suggested that the oxidative stress is involved in the cytotoxicity of NaBrO₃, and AT extract effectively protected NaBrO₃-induced cytotoxicity by antioxidative effects. Conclusively, the natural component like AT extract may be a putative therapeutic agent for the diminution or treatment of the cytotoxicity correlated with oxidative stress like hair dye component, NaBrO₃.

• Clinical and Experimental Reproductive Medicine
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• v.15 no.2
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• pp.149-155
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• 1988

To increase fertilization rate in vitro, separation of viable spermatozoa from the seminal plasma and its other components may be a useful procedure. Ejaculates from healthy men, whose semen analysis findings were normal in 19, and abnormal in 10, were filtered using the glass-wool filtration technique to yield a concentrated, viable sperm samples for IVF, and the usefulness and safety of this method were evaluated. The recovery rate of motile sperm in abnormal groups was 46.2% and 54.5% in normal group. The % motility was increased significantly compared with original sample after filtration, and the grade motility was improved, too. The sperm population with normal morphology was also increased significantly in both group. Using transmission electron microscopy, the ultrastructural integrity of acrosomal segment was examined in order to evaluate the potentially hazardous effect of glass-wool filtration to sperm head, however, sperm population with normal ultrastructure was increased compared with that of original ejaculate after separation. The filtered sperm was then processed for IVF, as the fertilizing capacity is the ultimate parameter of the sperm function. In abnormal group, the fertilization rate(41.5 %) and the ET rate per stimulated cycle were much lower than that of mormal group(69.6%). However, the cleavage rate and the number of embryos transfered per ET cycle were comparable with those of nomal group. The results suggest that the glass-wool filtration of sperm, particularly in oligo-asthenozoospsrmia, may be useful and safe method in the preparation of sperm for IVF.