Ki Young Dong

Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes

Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas.

Gas Sensing performance of composite materials using conducting polymer/single-walled carbon nanotubes

AbstractWe report the fabrication of a novel gas sensor that utilizes electrical resistance changes in electrically conductive polyaniline (PANI) and single-walled carbon nanotube (SWNT) composite materials and its sensing property when NH3 and CO gases co-existed. In addition, we investigated the concentration dependence of electrical properties of the PANI/SWNT composite material at room temperature using real-time monitoring. To improve the gas sensor properties, we deposited PANI using a drop-casting method to warp the PANI surrounding the SWNT. The PANI/SWNT composite material sensors showed a faster response to NH3 gas than CO gas. The CO gas increased the composite conductance, while the NH3 gas had the opposite effect.

Hydrophilic dots on hydrophobic nanopatterned surfaces as a flexible gas barrier.

The present study demonstrates a transparent polymeric gas barrier film mimicking the Namib Desert beetles back. SiO(2) hydrophilic dots have been deposited on a nanopatterned hydrophobic surface. A nanopatterned surface was fabricated by UV-curable nanoimprinting techniques. The surface energies of the hydrophobic and hydrophilic domains were 7.29 and >73.12 mN/m, respectively. The characteristics of water vapor transfer from hydrophobic to hydrophilic regions due to difference of the attractive force at interfaces are shown to yield the enhanced barrier performance according to the Ca degradation measurements. This strategy is suitable for organic electronics, solar cells, and plastic optics applications requiring moisture-free properties with high transmission.

Effect of plasma treatment on the gas sensor with single-walled carbon nanotube paste.

The effect of plasma treatment on the gas sensing properties of screen-printed single-walled carbon nanotube (SWCNT) pastes is reported. The gas sensors, using SWCNT pastes as a sensing material, were fabricated by photolithography and screen printing. The SWCNT pastes were deposited between interdigitated electrodes on heater membrane by screen printing. In order to functionalize the pastes, they were plasma treated using several gases which produce defects caused by reactive ion etching. The Ar and O(2) plasma-treated SWCNT pastes exhibited a large response to NO(2) exposure and the fluorinated gas, such as CF(4) and SF(6), plasma-treated SWCNT pastes exhibited a large response to NH(3) exposure.

Design of a multi-walled carbon nanotube field emitter with micro vacuum gauge

The variation of vacuum level inside a field emission device when electron is emitted from multi-walled carbon nanotubes (MWCNTs) by electric field was measured where MWCNT gauge packaged with a vacuum device was used to measure the degree of a vacuum until the end of the vacuum device life. It was found that the electrical properties of MWCNTs altered with the degree of a vacuum. We fabricated MWCNT gauge which were printed and pasted by the screen printer. In this paper, we report the successful detection of the ionization of gases in vacuum state.

Hydrophobic nanopatterning on a flexible gas barrier film by using a poly(dimethylsiloxane)elastomer

In this work, we fabricated a hydrophobic and transparent gas barrier film via a nanopatterned poly(dimethylsiloxane) elastomer imprinting on an ultraviolet-curable polymer resin. A Ca degradation method (water permeation rate) and surface energy measurements were used to determine the level of modification of the surface characteristics. As a result, the decreased surface energy from 25.8 to 7.29 mN m(-1) led to a lower water vapor transmission rate from 3.06 x 10(-1) to 6.24 x 10(-2) g m(-2) day(-1) according to the degree of decreased Ca height from 100 nm. A tunable wettability is beneficial for application where controlling the direction of moisture flow is important, such as in flexible organic electronics.

Noxious gas detection using carbon nanotubes with Pd nanoparticles

Noxious gas sensors were fabricated using carbon nanotubes [CNTs] with palladium nanoparticles [Pd NPs]. An increase in the resistance was observed under ammonia for both CNTs and CNT-Pd sensors. Under carbon monoxide [CO], the two sensors exhibited different behaviors: for CNT sensors, their resistance decreased slightly with CO exposure, whereas CNT-Pd sensors showed an increase in resistance. The sensing properties and effect of Pd NPs were demonstrated, and CNT-Pd sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective noxious gas sensor at room temperature.

Micro-pixel array of organic light-emitting diodes applying imprinting technique with a polymer replica

Efficient micro-pixel array of small molecule organic light-emitting diodes (OLEDs) has been fabricated by an imprinting technique which uses a polymer replica. To confirm the effect of the oxygen plasma for removing the residual layer, the performance of two kinds of OLEDs with varying thicknesses of resin as the micro-pixel array, have been compared. The measured results of the OLEDs have shown comparable device performances that are significantly characterized depending on the residues on the substrate. The performance of enhanced device has achieved efficiencies of 3.6 cd/A and 1.9 lm/W at 20 mA/cm2.

Scaling down of amorphous indium gallium zinc oxide thin film transistors on the polyethersulfone substrate employing the protection layer of parylene-C for the large-scale integration

We have investigated the parylene-groups for the device scaling-down as the protection layer of polyethersulfone (PES) substrate. In general, photolithography process on the PES substrate could not be allowed due to its poor chemical resistance. In this work, parylene-C is used as the protection layer. However, adhesion problem is observed caused by the hydrophobic property of parylene-groups. Thereby we additionally used SiO2 as the adhesion layer. Finally, we demonstrated the scaling-down of amorphous indium gallium zinc oxide thin film transistor on a plastic substrate by using lithography technique. Field-effect mobility, threshold voltage, current on-to-off ratio are measured to be 0.84 cm2/V s, 19.7 V, and 7.62×104, respectively.

Detection of CO and NH 3 mixed gas using single-walled carbon nanotubes

We fabricated a carbon nanotube based gas sensor for the detection of CO and NH3 mixed gas. Conventional photolithography technology was applied for the localization of sensing materials and the sensor fabrication. Single walled carbon nanotubes were dispersed in Sodium Dodecyl Sulfate(SDS) solution. The whole surface was covered by a photoresist except window areas between two electrodes. Carbon nanotubes were carefully dropped over the window areas and dried at 220°C over a hot plate. Then, the photoresist was removed using acetone. CO and NH3 mixed gas was delivered into a chamber at room temperature with nitrogen as a carrier gas. For comparison, each gas was applied to our sensor separately. Electrical resistance was measured for sensing performance.