• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.337-337
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• 2012

Dye sensitized solar cell (DSSC) having high efficiency with low cost was first reported by Gr$\ddot{a}$tzel et al. Many DSSC research groups attempt to enhance energy conversion efficiency by modifying the dye, electrolyte, Pt-coated electrode, and $TiO_2$ films. However, there are still some problems against realization of high-sensitivity DSSC such as the recombination of injected electrons in conduction band and the limited adsorption of dye on $TiO_2$ surface. The surface of $TiO_2$ is very important for improving hydrophilic property and dye adsorption on its surface. In this paper, we report a very efficient method to improve the efficiency and stability of DSSC with nano-structured $TiO_2$. Atmospheric plasma system was utilized for nitrogen plasma treatment on nano-structured $TiO_2$ film. We confirmed that the efficiency of DSSC was significantly dependent on plasma power. Relative in the $TiO_2$ surface change and characteristics after plasma was investigated by various analysis methods. The structure of $TiO_2$ films was examined by X-ray diffraction (XRD). The morphology of $TiO_2$ films was observed using a field emission scanning electron microscope (FE-SEM). The surface elemental composition was determined using X-ray photoelectron spectroscopy (XPS). Each of plasma power differently affected conversion efficiency of DSSC with plasma-treated $TiO_2$ compared to untreated DSSC under AM 1.5 G spectral illumination of $100mWcm^{-2}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.511-512
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• 2006

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.05a
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• pp.29.2-29.2
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• 2008

• Journal of Life Science
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• v.21 no.12
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• pp.1710-1715
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• 2011

The bactericidal effect of nano plasma ion (NPi) which was generated by NPi was analyzed using different kinds of microorganisms, exposure times, chamber sizes, ion amounts and distance. As the result of Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Klebsiella pneumoniae, Staphylococcus aureus and Bacillus subtilis were shown different in decrement. Gram-negative bacteria E. coli showed the highest percentage (96.57%) and Gram-positive bacteria B. subtilis which produced spore has the lowest percentage (57.41%). From the exposure time of NPi most of the microorganisms were extinct at an early stage. According to the size of the chamber we compared the loss of E.coli and the experiment result shown, analyzed NPi using 5 chambers $0.005m^3$ to $30m^3$ for 2 hr, that when volume of the chamber increased, saturation ion and bactericidal effect was decreased. In addition, an NPi generator installed in the $1m^3$ chamber investigated the decrement of E. coli. Saturation ion concentration increased with decrement. Finally, E. coli showed a similar reduction according to the distance from NPi generator.

• Applied Microscopy
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• v.52
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• pp.4.1-4.11
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• 2022

Field emission scanning electron microscopy (FESEM) is an essential tool for observing surface details of specimens in a high vacuum. A series of specimen procedures precludes the observations of living organisms, resulting in artifacts. To overcome these problems, Takahiko Hariyama and his colleagues proposed the concept of the "nanosuit" later referred to as "NanoSuit", describing a thin polymer layer placed on organisms to protect them in a high vacuum in 2013. The NanoSuit is formed rapidly by (i) electron beam irradiation, (ii) plasma irradiation, (iii) Tween 20 solution immersion, and (iv) surface shield enhancer (SSE) solution immersion. Without chemical fixation and metal coating, the NanoSuit-formed specimens allowed structural preservation and accurate element detection of insulating, wet specimens at high spatial resolution. NanoSuit-formed larvae were able to resume normal growth following FESEM observation. The method has been employed to observe unfixed and uncoated bacteria, multicellular organisms, and paraffin sections. These results suggest that the NanoSuit can be applied to prolong life in vacuo and overcome the limit of dead imaging of electron microscopy.

• Journal of Powder Materials
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• v.20 no.2
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• pp.120-124
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• 2013

This study is carried out to develop the new process for the fabrication of ultra-fine electrodes on the flexible substrates using superhydrophobic effect. A facile method was developed to form the ultra-fine trenches on the flexible substrates treated by plasma etching and to print the fine metal electrodes using conductive nano-ink. Various plasma etching conditions were investigated for the hydrophobic surface treatment of flexible polyimide (PI) films. The micro-trench on the hydrophobic PI film fabricated under optimized conditions was obtained by mechanical scratching, which gave the hydrophilic property only to the trench area. Finally, the patterning by selective deposition of ink materials was performed using the conductive silver nano-ink. The interface between the conductive nanoparticles and the flexible substrates were characterized by scanning electron microscope. The increase of the sintering temperature and metal concentration of ink caused the reduction of electrical resistance. The sintering temperature lower than $200^{\circ}C$ resulted in good interfacial bonding between Ag electrode and PI film substrate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.1
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• pp.27-30
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• 2013

Catalyst-free graphene nano-sheets without substrates have been synthesized using fullerene and a high direct current (dc) pulse in the spark plasma sintering (SPS) process. Graphene nano-sheets were synthesized directly in the gas phase of carbon atoms which are generated from fullerene at a temperature of $600^{\circ}C$. Characterization has been carried out by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).

• The Journal of the Korean dental association
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• v.54 no.12
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• pp.985-995
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• 2016

Titanium (Ti) has been widely used for dental implant due to great biocompatibility and bonding ability against natural alveolar bone. A lot of titanium surface modification has been introduced in dentistry and, among them, methods to introduce micro/nano-roughened surface were considered as clinically approved strategy for accelerating osseointegration of Ti dental implant. To have synergetic effect with topography oriented favors in cell attachment, chair-side surface treatment with reproducibility of micro/nano-topography is introduced as next strategy to further enhance cellular functionalities. Extensive research has been investigated to study the potential of micro/nano-topography preserved chair-side surface treatment for Ti dental implant. This review will discuss ultraviolet, low level of laser therapy and non-thermal atmospheric pressure plasma on Ti dental implant with micro/nano-topography as next generation of surface treatment due to its abilities to induce super-hydrophilicity or biofunctionality without change of topographical cues.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.505-509
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• 2009

In this study, bulk nano-crystalline $Si_3N_4$ ceramics were fabricated by spark plasma sintering (SPS) and their mechanical properties, in particular wear, were investigated. A wide range of grain sizes, from 80 nm and 250 nm were obtained by varying sintering conditions ($1550^{\circ}C$-5 min to $1650^{\circ}C$-20 min). The elastic modulus of obtained ceramics was ${\sim}250$ GPa and hardness was in the range of $13{\sim}14$ GPa. The indentation fracture toughness increased from $2.58MPa{\cdot}m^{1/2}$ to $3.24MPa{\cdot}m^{1/2}$ with increasing sintering temperature possibly due to the elongated grains. Sliding wear tests revealed at least an order magnitude improvement in wear resistance with grain refinement. Microstructure analysis indicated that nano-$Si_3N_4$ specimens worn mainly through delamination and microcracking, while that of coarser specimens revealed severe wear with grain debonding and fracture.

• Proceedings of the Korean Vacuum Society Conference
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• 2002.02a
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• pp.110-110
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• 2002