• Korean Journal of Materials Research
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• v.29 no.2
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• pp.87-91
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• 2019

We report on stretchable electrochromic films of poly(3-hexylthiophene) (P3HT) fabricated on silver nanowire (AgNW) electrodes. AgNWs electrodes are prepared on polydimethylsiloxane (PDMS) substrates using a spray coater for stretchable electrochromic applications. On top of the AgNW electrode, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is introduced to ensure a stable resistance over the electrode under broad strain range by effectively suppressing the protrusion of AgNWs from PDMS. This bilayer electrode exhibits a high performance as a stretchable substrate in terms of sheet resistance increment by a factor of 1.6, tensile strain change to 40 %, and stretching cycles to 100 cycles. Furthermore, P3HT film spin-coated on the bilayer electrode shows a stable electrochromic coloration within an applied voltage, with a color contrast of 28.6 %, response time of 4-5 sec, and a coloration efficiency of $91.0cm^2/C$. These findings indicate that AgNWs/PEDOT:PSS bilayer on PDMS substrate electrode is highly suitable for transparent and stretchable electrochromic devices.

• New & Renewable Energy
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• v.18 no.1
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• pp.29-34
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• 2022

The most prevalent cause of solar cell efficiency loss is reduced recombination at the metal electrode and silicon junction. To boost efficiency, a a SiO_X/poly-Si passivating interface is being developed. Poly-Si for passivating contact is formed by various deposition methods (sputtering, PECVD, LPCVD, HWCVD) where the ploy-Si characterization depends on the deposition method. The sputtering process forms a dense Si film at a low deposition rate of 2.6 nm/min and develops a low passivation characteristic of 690 mV. The PECVD process offers a deposition rate of 28 nm/min with satisfactory passivation characteristics. The LPCVD process is the slowest with a deposition rate of 1.4 nm/min, and can prevent blistering if deposited at high temperatures. The HWCVD process has the fastest deposition rate at 150 nm/min with excellent passivation characteristics. However, the uniformity of the deposited film decreases as the area increases. Also, the best passivation characteristics are obtained at high doping. Thus, it is necessary to optimize the doping process depending on the deposition method.

• Composites Research
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• v.28 no.3
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• pp.75-80
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• 2015

Poly(vinylidene fluoride-trifluoroethylene; P(VDF-TrFE)) is one of the most promising electroactive polymers with numerous application potentials in many fields of industry. Because of its good electro-mechanical properties P(VDF-TrFE) has been used for a number of sensors and actuators and also can be used for monitoring composite structure behaviors as a sensor. Three different ways (Electrical poling, annealing-cooling, and pressing) to enhance ${\beta}$-phase of P(VDF-TrFE) film were carried out. A microscopic analysis was conducted using X-ray diffraction to investigate the effect of such treatments on piezoelectric properties of P(VDF-TrFE) film. From the results, poling, annealing-cooling, and pressing were all effective to enhance ${\beta}$ crystallinity of P(VDF-TrFE) film and the maximum increase rate was 62.80% from 45.29% of the control group.

• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.141-152
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• 2001

Eliminating the infecting bacteria of the root canal system and preventing reinfection must be the main objectives of all endodontic works. None of commercially available root canal sealers have the properties of desirable tissue compatibility and strong antibacterial activity. The purpose of this study is to develope an ideal root canal sealer using commercially available polyphosphate (polyP), Calgon, which is known to be antibacterial and safe. For the study. resin type AH26, zinc oxide eugenol type Tubli Seal. Ca(OH)$_2$ type Apexit as base sealers for polyP (0~3%) and para formaldehyde containing N2 as a control base were selected. Specimens (3$\times$4mm) of the sealers were prepared in a 37$^{\circ}C$ incubator for 3 and 10 days and their antibacterial activity against streptococci and black pigmented anaerobic rods was observed using an agar diffusion method. The result were as follows: 1. Among 3 day old root canal sealers. N2 as a positive control showed the strongest antibacterial effect. followed by AH26. Tubli Seal and. Apexit which barely showed antibacterial activity against the test bacteria. In contrast. 10 day old AH26 showed a greater antibacterial activity than 10 day old N2. 2. All sealer specimens showed a greater antibacterial activity against black pigmented anaerobic rods than streptococci. Three day old ones appeared to be more antibacterial than 10 day old ones except for Apexit. 3. As compared to N2, 3 day old AH26 demonstrated a similar antibacterial activity against black pig mented anaerobic rods but to a lesser extent to streptococci. Ten day old AH26 showed a greater antibacterial activity against black pigmented anaerobic rods than 10 day old N2. 4. As compared to AH26. Tubli Seal generally revealed a lower antibacterial activity but it showed a greater antibacterial activity aginst S. gordonii Challis. 5. Enhancement of antibacterial activity by polyP was more clearly observed when it was added to Ca(OH)$^{\circ}C$ based root canal sealers. Tubli Seal and N2. 6. The addition of polyP enhanced the antibacterial activity of 3 day old AH26 against S. gordonii G9B (16%) and Challis (29%), and P. gingivalis 2561 (24%) only. Moreover, polyP failed to increase antibacterial activity of 10 day old AH26 against the test strains but P. gingivalis A7A1 28(13%). 7. The addition of polyP increased the antibacterial effect of 3 day old Tubli Seal on several test bacteria including s. mutans GS 5 (50%). s. gordonii G9B (47%) and Challis (122%). and all the test strains of P. gingivalis (13~35%) except for 9 14K 1. The addition of polyP to 10 day old Tubli Seal increased antibacterial activity of the root canal sealer against most test strains. 8. 3 day old Apexit failed to show antibacterial activity. if any very little against S. mutans GS 5 and Pr. intermedia ATCC 49046. However. polyP increased its antibacterial activity by 50 and 69%, respectively. Increase of antibacterial activity of 10 day old Apexit by polyP was more clearly observed than that of 3 day old one.

• Korean Journal of Microbiology
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• v.36 no.4
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• pp.299-305
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• 2000

Degradation behavior of the three commercial biodegradable polymers, namely poly(3-hydroxybutyrate) (PHB) Sky-Green/sup R/ (SG) and Mater-Bi/sup R/ (MB) was investigated using bacteria isolated from activated sludge and farm soil. Three PHB degrading bacteria, three SG degrading bacteria and one MB degrading bacteria were isolated. The PHB degrading bacteria were identified to be Flavimonas oryzihabitans, Corynebacterium pseudodiphtheriticum and Micrococcus diversus, while Pseudomonas vesicuraris, Pasteurlla multocida and Flavobacterium odoratum were identified as SG degrading bacteria. As for MB, Pseudomonas vesicuraris was isolated. The shake flask test for 28 days indicated that the rate of biodegradation of PHB, SG and MB in terms of weight loss were about 44∼69% 25∼32% and 29% respectively. The surface morphology of PHB, SG andMB films before and after degradation by microorganisms in an activated sludge soil was observed under SEM, demonstrating that the film surface had a very porous structure, and that microorganisms colonized heavily on the film surface. TOC and pH variation as a result of abiotic hydrolysis, or microbial growth in the absence of the polymers were compared to those due to degradation by F. oryzihabitans. Abiotic hydrolysis of PHB was three times as fast as that of SG and MB. Addition of yeast extract to the basal liquid medium accelerated the biodegradation of the polymers. Biodegradation of PHB was always faster than that of SG and MB irrespectively of the presence of yeast extract in the basal liquid medium.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.680-684
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• 2018

We investigate the effect of light intensity and wavelength of a solar cell device using photoconductive atomic force microscopy(PC-AFM). A $POCl_3$ diffusion doping process is used to produce a p-n junction solar cell device based on a polySi wafer, and the electrical properties of prepared solar cells are measured using a solar cell simulator system. The measured open circuit voltage($V_{oc}$) is 0.59 V and the short circuit current($I_{sc}$) is 48.5 mA. Moreover, the values of the fill factors and efficiencies of the devices are 0.7 and approximately 13.6 %, respectively. In addition, PC-AFM, a recent notable method for nano-scale characterization of photovoltaic elements, is used for direct measurements of photoelectric characteristics in limited areas instead of large areas. The effects of changes in the intensity and wavelength of light shining on the element on the photoelectric characteristics are observed. Results obtained through PC-AFM are compared with the electric/optical characteristics data obtained through a solar simulator. The voltage($V_{PC-AFM}$) at which the current is 0 A in the I-V characteristic curves increases sharply up to $18W/m^2$, peaking and slowly falling as light intensity increases. Here, $V_{PC-AFM}$ at $18W/m^2$ is 0.29 V, which corresponds to 59 % of the average $V_{oc}$ value, as measured with the solar simulator. Furthermore, while the light wavelength increases from 300 nm to 1,100 nm, the external quantum efficiency(EQE) and results from PC-AFM show similar trends at the macro scale but reveal different results in several sections, indicating the need for detailed analysis and improvement in the future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.821-825
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• 2015

Anti-reflective (AR) thin film was fabricated on a glass substrate by sol-gel method. The coating solution was synthesized with TEOS (tetraethlyorthosilicate) and poly ethylene glycol (PEG, 4.0 wt%). As the withdrawal speed of coating was changed from 0.1 mm/sec to 0.3 mm/sec, the thickness and refractive index of prepared thin films were changed. The reflectance and transmittance of coating glass fabricated by the withdrawal speed of 0.1 mm/sec were 0.62% and 95.0% in visible light range. The refractive index and thickness of single layer thin film were n= 1.29 and ca. 99.0 nm.

• Archives of Pharmacal Research
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• v.29 no.8
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• pp.707-711
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• 2006

Bifidobacteria-loaded alginate poly-l-lysine microparticles (bap microparticles) were prepared using an air atomization method and then freeze-dried. The viability of the bap microparticles was investigated as a function of the amount of the bifidobacteria cultures, and the addition of a yeast extract, cryoprotectants, antioxidants and neutralizer. The size of the bap microparticles with and without the bifidobacteria was $84.8{\pm}28.5\;{\mu}m$ ($mean{\pm}standard$ deviation) and $113.1{\pm}38.5\;{\mu}m$, respectively. The surface morphology was slightly ellipsoid and wrinkled regardless of the incorporating bifidobacteria. The viability gradually decreased with increasing freeze-drying time. Free-flowing powdered bap microparticles were obtained at least 12 h after freeze-drying the wetted slurry of bap microparticles. However, the particles tended to aggregate when either lactose or ascorbic acid was added. The addition of a yeast extract, cryoprotectants (glycerol and lactose), antioxidants ($NaHSO_3$ and ascorbic acid) and neutralizer $(Mg_3(PO_4)_2)$ resulted in a significantly higher viability of the bifidobacteria in the bap microparticles after freeze-drying (0.34-1.84 log) compared with the culture alone.

• Applied Chemistry for Engineering
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• v.22 no.1
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• pp.15-20
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• 2011

Poly[2,3-dimethyl-5,8-dithiophene-2-yl-quinoxaline-alt-9,9-dihexyl-9H-fluorene] (PFTQT) and poly[2,3-dimethyl-5,8-dithiophen-2-yl-quinoxaline-alt-10-hexyl-10H-phenothiazine (PPTTQT) based on 2,3-dimethyl-5,8-dithiophen-2-yl-quinoxaline weresynthesized by Suzuki coupling reaction. All polymers were soluble in common organic solvents such as chloroform, chlorobenzene, o-dichlorobenzene, tetrahydrofuran (THF) and toluene. The maximum absorption wavelength and band gap of PFTQT were 440 nm and 2.30 eV, and PPTTQT were 445 nm and 2.23 eV, respectively. The HOMO and LUMO energy level of PFTQT were -6.05 and -3.75 eV, and PPTTQT were -5,89 and -3.66 eV, respectively. The organic photovoltaic devices based on the blend of polymer and PCBM (1 : 2 by weight ratio) were fabricated. Efficiencies of devices were 0.24% (PFTQT) and 0.16% (PPTTQT), respectively. The short circuit current density ($J_{sc}$), fill factor (FF), and open circuit voltage ($V_{oc}$) of the device with PFTQT were $0.97mA/cm^2$, 29% and 0.86 V, and the device based on PPTTQT were $0.80mA/cm^2$, 28% and 0.71 V, 31% and 0.71 V, respectively, under air mass (AM) 1.5 G and 1 sun condition ($100mA/cm^2$).

• Journal of Life Science
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• v.29 no.9
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• pp.941-948
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• 2019

Colorectal cancer is a major health problem in industrialized countries. Ziyuglycoside II ($3{\beta}-3-{\alpha}$-1- arabinopyranosyloxy-19-hydroxyurs-12-en-28-oicacid), a triterpenoid saponin isolated from the roots of Sanguisorba officinalis L., possesses antioxidant, antiangiogenic, and anticancer properties. However, the therapeutic function of ziyuglycoside II in colitis-associated colorectal carcinogenesis is undefined. In the present study, the effect of ziyuglycoside II on colitis-associated colon cancer induced in mice using azoxymethane (AOM)/dextran sulfate sodium (DSS) was explored. The AOM model recapitulates many features of human colon cancer, but it lacks an inflammatory component. DSS induces colitis and promotes AOM-induced colon cancer in mice. BALB/c mice were injected with AOM and administered 2% DSS in drinking water. The mice were given ziyuglycoside II (1 or 5 mg/kg) orally three times per week, and colonic tissue was collected at 64 days. Administration of ziyuglycoside II markedly diminished the formation of colonic tumors. Western blot and immunohistological analyses showed that ziyuglycoside II noticeably decreased nuclear factor kappa-B-positive cells and levels of inflammation-related proteins, such as inducible nitric oxide synthase, cyclooxygenase-2, tumor necrosis factor-${\alpha}$, and interleukin-6 in colon tissue. It also prompted apoptosis. Ziyuglycoside II treatment augmented cleaved forms of caspase-3, caspase-7, and poly (ADP-ribose) polymerase in colonic tissues. In conclusion, ziyuglycoside II could defend against colitis-associated tumorigenesis in mice by inhibiting inflammation and inducing apoptosis. This shows a promising chemopreventive potential for its use in colitis-associated colon cancer.