• Advances in nano research
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• 제1권2호
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• pp.71-82
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• 2013

A simple chemical precipitation technique is reported for the synthesis of a hybrid nanostructure of single-wall carbon nanotubes (SWCNT) and titania ($TiO_2$) nanocrystals of average size 5 nm, which may be useful as a prominent photocatalytic material with improved functionality. The synthesized hybrid structure has been characterized by transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDAX), powder X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. It is clearly revealed that nearly monodispersed titania nanocrystals (anatase phase) of average size 5 nm decorate the surfaces of SWCNT bundles. The UV-vis absorption study shows a blue shift of 16 nm in the absorbance peak position of the composite material compared to the unmodified SWCNTs. The photoluminescence study shows a violet-blue emission in the range of 325-500 nm with a peak emission at 400 nm. The low temperature electrical transport property of the synthesized nanomaterial has been studied between 77-300 K. The DC conductivity shows semiconductor-like characteristics with conductivity increasing sharply with temperature in the range of 175-300 K. Such nanocomposites may find wide applications as improved photocatalyst due to transfer of photo-ejected electrons from $TiO_2$ to SWCNT, thus reducing recombination, with the SWCNT scaffold providing a firm and better positioning of the catalytic material.

• 에너지공학
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• 제27권3호
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• pp.48-56
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• 2018

The shell waste biomineralization process has known a tremendous metamorphosis and also the nanostructure with the identification of matrix proteins in oyster shells. However, proteins are represented in minor shell components and they are the major macromolecules that control biocrystal synthesis. Aragonite and calcite were derived from molluscan shells and evaluated the source of carbonate minerals and it helps for the formation of limestone. The oyster shell wastes are large and massive. The paleoecological study of oyster beds has discovered a near-shore and thin Upper Rudeis formation with storm influence during the accumulation of oysters with highly altered by disarticulation, bioerosion, and encrustation. It is possible even in the Paleozoic mollusks provided sufficient carbonate entirely to the source of microcrystalline of limestone. The present review is to discuss paleoecologically a number of oyster shell beds accumulated and sediment to form the different types of limestone during the Middle Miocene time.

• Journal of Electrochemical Science and Technology
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• 제1권1호
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• pp.10-18
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• 2010

Controlled electrodeposition of dendritic nano-structured gold-platinum (AuPt) alloy onto an electrochemically pretreated carbon paper substrate was conducted in an attempt to improve catalyst utilization and to secure an electronic percolation network toward formic acid (FA) fuel cell application. The AuPt catalysts were obtained by potentiostatic deposition. AuPt catalysts synthesized as bimetallic alloys with 60% Au content exhibited the highest catalytic activity towards formic acid electro-oxidation. The origin of this high activity and the role of Au were evaluated, in particular, by XPS analysis. Polarization and stability measurements with 1 mg $cm^{-2}$ AuPt catalyst (only 0.4 mg $cm^{-2}$ Pt) showed 52 mW $cm^{-2}$ and sustainable performance using 3M formic acid and dry air at $40^{\circ}C$.

• Korean Chemical Engineering Research
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• 제43권4호
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• pp.439-451
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• 2005

수소저장기술은 수소경제를 달성하기 위해 개발해야할 핵심요소기술이다. 이 논문에서는 고체수소저장기술의 최신 개발 동향을 고찰하였다. 나노구조 탄소계 물질(nanostructured carbon materials), 유기금속구조물(metal organic framework, MOFs), 금속수소화물(metal hydrides), 클래스레이트수화물(clathrate hydrates), 금속착수소화물(complex chemical hydrides)과 같은 고체수소저장매체를 중점적으로 고찰하였다. 그 결과 지금까지 개발된 고체수소저장재료의 수소저장용량은 고체의 표면적에 비례하여 증가함을 알 수 있었다. 또한 수송용 탑재형 수소저장 응용을 목적으로 안전하면서도 가역적 고밀도 수소저장이 가능한 기능성 신 나노재료의 개발 방향을 제시하였다.

• 한국재료학회지
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• 제20권10호
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• pp.513-517
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• 2010

There have been many efforts to modify and improve the properties of functional thin films by hybridization with nano-sized materials. For the fabrication of electronic circuits, micro-patterning is a commonly used process. For photochemical metal-organic deposition, photoresist and dry etching are not necessary for microscale patterning. We obtained direct-patternable $SnO_2$ thin films using a photosensitive solution containing Ag nanoparticles and/or multi-wall carbon nanotubes (MWNTs). The optical transmittance of direct-patternable $SnO_2$ thin films decreased with introduction of nanomaterials due to optical absorption and optical scattering by Ag nanoparticles and MWNTs, respectively. The crystallinity of the $SnO_2$ thin films was not much affected by an incorporation of Ag nanoparticles and MWNTs. In the case of mixed incorporation with Ag nanoparticles and MWNTs, the sheet resistance of $SnO_2$ thin films decreased relative to incorporation of either single component. Valence band spectral analyses of the nano-hybridized $SnO_2$ thin films showed a relation between band structural change and electrical resistance. Direct-patterning of $SnO_2$ hybrid films with a line-width of 30 ${\mu}m$ was successfully performed without photoresist or dry etching. These results suggest that a micro-patterned system can be simply fabricated, and the electrical properties of $SnO_2$ films can be improved by incorporating Ag nanoparticles and MWNTs.

• Journal of Information Display
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• 제12권3호
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• pp.145-152
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• 2011

Since the discovery of fullerenes as a class of nanostructure compounds, many potential applications have been suggested for their unusual structures and properties. The isolated pentagon rule (IPR) states that all pentagonal carbon rings are isolated in the most stable fullerene. Fullerenes $C_n$ are a class of spherical carbon allotrope group with unique properties. Electron transfer between fullerenes and other molecules is thought to involve the transfer of electrons between the molecules surrounding the fullerene cage. One class of electron transfer molecules is the methanofullerene derivatives ([6,6]-phenyl $C_{61}$-butyric acid methyl ester (PCBM), 4-(2-ethylhexyloxy)-[6,6]-phenyl $C_{61}$-butyric acid methyl ester (p-EHO-PCBM), and 4-(2-ethylhexyloxy)-[6,6]-phenyl $C_{61}$-butyric acid (p-EHO-PCBA), 10-12). It has been determined that $C_{60}$ does not obey IPR. Supramolecular complexes 1-9 and 10-12 are shown to possess a previously unreported host.guest interaction for electron transfer processes. The unsaturated, cis-geometry, thiocrown ethers, (1-9) (described as [X-UT-Y], where X and Y indicate the numbers of carbon and sulfur atoms, respectively), are a group of crown ethers that display interesting physiochemical properties in the light of their conformational restriction compared with a corresponding saturated system, as well as the sizes of their cavities. Topological indices have been successfully used to construct mathematical methods that relate structural data to various chemical and physical properties. To establish a good relationship between the structures of 1-9 with 10-12, a new index is introduced, ${\mu}_{cs}$. This index is the ratio of the sum of the number of carbon atoms ($n_c$) and the number of sulfur atoms ($n_s$) to the product of these two numbers for 1-9. In this study, the relationships between this index and oxidation potential ($^{ox}E_1$) of 1-9, as well as the first to third free energies of electron transfer (${\Delta}G_{et(n)}$, for n = 1-3, which is given by the Rehm-Weller equation) between 1-9 and PCBM, p-EHO-PCBM, and p-EHO-PCBA (10-12) as [X-UT-Y]@R(where R is the adduct PCBM, p-EHO-PCBM, and p-EHO-PCBA group) (13-15) supramolecular complexes are presented and investigated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.369-369
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• 2016

A nanostructure composite is a highly suitable substance for photoacoustic ultrasound generation. This allows an input laser beam (typically, nanosecond pulse duration) to be efficiently converted to an ultrasonic output with tens-of-MHz frequency. This type of energy converter has been demonstrated by using a carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite film that exhibit high optical absorption, rapid heat transition, and mechanical durability, all of which are necessary properties for high-amplitude ultrasound generation. In order to develop the CNT-PDMS composite film, a high-temperature chemical vapor deposition (HTCVD) method has been commonly used so far to grow CNT and then produce a CNT-PDMS composite structure. Here, instead of the complex HTCVD, we use a mixed solution of hydrophobic multi-walled CNT and dimethylformamid (DMF) and fabricate a solution-processed CNT-PDMS composite film over a spherically concave substrate, i.e. a focal energy converter. As the solution process can be applied over a large area, we could easily fabricate the focal transmitter that focuses the photoacoustic output at the moment of generation from the CNT-PDMS composite layer. With this method, we developed photoacoustic energy converters with a large diameter (>25 mm) and a long focal length (several cm). The lens performance was characterized in terms of output pressure amplitude for an incident pulsed laser energy and focal spot dimension in both lateral and axial. Due to the long focal length, we expect that the new lens can be applied for long-range ultrasonic treatment, e.g. biomedical therapy.

• 한국재료학회지
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• 제20권5호
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• pp.235-240
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• 2010

We investigated the carbon monoxide (CO) gas-sensing properties of nanostructured Al-doped zinc oxide thin films deposited on self-assembled Au nanodots (ZnO/Au thin films). The Al-doped ZnO thin film was deposited onto the structure by rf sputtering, resulting in a gas-sensing element comprising a ZnO-based active layer with an embedded Pt/Ti electrode covered by the self-assembled Au nanodots. Prior to the growth of the active ZnO layer, the Au nanodots were formed via annealing a thin Au layer with a thickness of 2 nm at a moderate temperature of $500^{\circ}C$. It was found that the ZnO/Au nanostructured thin film gas sensors showed a high maximum sensitivity to CO gas at $250^{\circ}C$ and a low CO detection limit of 5 ppm in dry air. Furthermore, the ZnO/Au thin film CO gas sensors exhibited fast response and recovery behaviors. The observed excellent CO gas-sensing properties of the nanostructured ZnO/Au thin films can be ascribed to the Au nanodots, acting as both a nucleation layer for the formation of the ZnO nanostructure and a catalyst in the CO surface reaction. These results suggest that the ZnO thin films deposited on self-assembled Au nanodots are promising for practical high-performance CO gas sensors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.288-288
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• 2013

Lithium-ion battery (LIB) is one of the most important rechargeable battery and portable energy storage for the electric digital devices. In particular, study about the higher energy capacity and longer cycle life is intensively studied because of applications in mobile electronics and electric vehicles. Generally, the LIB's capacity can be improved by replacing anode materials with high capacitance. The graphite, common anode materials, has a good cyclability but shows limitations of capacity (~374 mAh/g). On the contrary, silicon (Si) and germanium(Ge), which is same group elements, are promising candidate for high-performance LIB electrodes because it has a higher theoretical specific capacity. (Si:4200 mAh/g, Ge:1600 mAh/g) However, it is well known that Si volume change by 400% upon full lithiation (lithium insertion into Si), which result in a mechanical pulverization and poor capacity retention during cycling. Therefore, variety of nanostructure group IV elements, including nanoparticles, nanowires, and hollow nanospheres, can be promising solution about the critical issues associated with the large volume change. However, the fundamental research about correlation between the composition and structure for LIB anode is not studied yet. Herein, we successfully synthesized various structure of nanowire such as Si-Ge, Ge-Carbon and Si-graphene core-shell types and analyzed the properties of LIB. Nanowires (NWs) were grown on stainless steel substrates using Au catalyst via VLS (Vapor Liquid Solid) mechanism. And, core-shell NWs were grown by VS (Vapor-Solid) process on the surface of NWs. In order to characterize it, we used FE-SEM, HR-TEM, and Raman spectroscopy. We measured battery property of various nanostructures for checking the capacity and cyclability by cell-tester.

• Nano
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• 제13권10호
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• pp.1850124.1-1850124.12
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• 2018

$TiO_2$ films were deposited from oxygen/titanium tetraisopropoxide (TTIP) plasmas at low temperature by Helicon-PECVD at floating potential ($V_f$) or substrate self-bias of -50 V. The influence of titanium precursor partial pressure on the morphology, nanostructure and optical properties was investigated. Low titanium partial pressure ([TTIP] < 0.013 Pa) was applied by controlling the TTIP flow rate which is introduced by its own vapor pressure, whereas higher titanium partial pressure was formed through increasing the flow rate by using a carrier gas (CG). Then the precursor partial pressures [TTIP+CG] = 0:027 Pa and 0.093 Pa were obtained. At $V_f$, all the films exhibit a columnar structure, but the degree of inhomogeneity is decreased with the precursor partial pressure. Phase transformation from anatase ([TTIP] < 0.013 Pa) to amorphous ([TTIP+CG] = 0:093 Pa) has been evidenced since the $O^+_2$ ion to neutral flux ratio in the plasma was decreased and more carbon contained in the film. However, in the case of -50 V, the related growth rate for different precursor partial pressures is slightly (~15%) decreased. The columnar morphology at [TTIP] < 0.013 Pa has been changed into a granular structure, but still homogeneous columns are observed for [TTIP+CG] = 0:027 Pa and 0.093 Pa. Rutile phase has been generated at [TTIP] < 0:013 Pa. Ellipsometry measurements were performed on the films deposited at -50 V; results show that the precursor addition from low to high levels leads to a decrease in refractive index.