Yang Doo Lee

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.

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.

Sensing properties of polyethylenimine coated carbon nanotubes in oxidized oil.

Chemical detection is still a continuous challenge when it comes to designing single-walled carbon nanotube (SWCNT) sensors with high selectivity, especially in complex chemical environments. A perfect example of such an environment would be in thermally oxidized soybean oil. At elevated temperatures, oil oxidizes through a series of chemical reactions that results in the formation of monoacylglycerols, diacylglycerols, oxidized triacylglycerols, dimers, trimers, polymers, free fatty acids, ketones, aldehydes, alcohols, esters, and other minor products. In order to detect the rancidity of oxidized soybean oil, carbon nanotube chemiresistor sensors have been coated with polyethylenimine (PEI) to enhance the sensitivity and selectivity. PEI functionalized SWCNTs are known to have a high selectivity towards strong electron withdrawing molecules. The sensors were very responsive to different oil oxidation levels and furthermore, displayed a rapid recovery of more than 90% in ambient air without the need of heating or UV exposure.

Fabrication and field emission properties of spray-deposited RNA-carbon nanotube films

Carbon nanotubes (CNTs) were effectively dispersed and functionalized by being wrapped with RNA. The RNA-CNT hybrids attached strongly to an indium tin oxide (ITO) glass substrate and formed a uniform film, making it possible to use field emitters for field emission applications. An electron field emission cathode was fabricated with a spray method using these RNA-CNT hybrids. Well-defined RNA-CNT patterns were obtained on the ITO glass substrate. The cathode showed a uniform emission pattern across the entire surface and also exhibited a high current density. The RNA-CNT hybrids compared favorably to other factionalized CNTs for use in the spray method.

53.2: Characteristics of Field Emission from Printed Carbon Nanotubes by Physical Surface Treatments

We investigated field emission properties modify surface morphology of printed CNTs and align CNTs vertically by physical surface treatments such as roller and tapping, also suggest that surface treatment apply to the once electric field keeping method for increase the number of emission sites in the printed CNT cathode.

Field-emission X-ray sources with an anisotropic focusing lens for isotropic X-ray focal spots

Hermetic-sealed field-emission X-ray sources with an anode voltage and current of 70 kV and 0.5 mA have been developed using an anisotropic focusing electron lens structure for an isotropic focal spot. The anisotropic focusing of an electron beam was achieved using an electrostatic electron lens with anisotropic aperture geometry integrated in a gate (or grid) electrode. The anisotropic geometry has an influence on the electron beam with different horizontal and vertical electric fields, thereby anisotropically focusing the beam on an anode target.

Influence of field emission on agglomerated carbon nanotubes in pastes

The authors have studied the modification of surface morphologies of screen-printed carbon nanotube (CNT) film by a liquid pretreatment and the agglomeration influence of CNT emitters. Liquid pretreatments before and after heat treatment are efficient as a removal process for organic binders for the improvement of field emission. In addition, this method enables to entangle an emitter to free individual standing CNTs.

Field emission characteristics of patterned carbon nanotubes on metal substrate

Multi-walled carbon nanotubes were fabricated KOVAR substrates using electrophoretic deposition (EPD). The surface treatments of the substrate were performed by palladium coating process which is an activation procedure for electroless plating. Through the surface treatments, the roughness of the surface increased and cathodes which have high roughness factor showed better field emission characteristics compared to non-treated ones.

The effect of Au nanoparticle on metal organic semiconductor field effect transistor on plastic substrate by transfer method

We report on organic nonvolatile memory devices, using pentacene as the active semiconductor layer and gold nanoparticles (Au NPs) array as charge storage elements. An effective and facile fabrication by self-assembly of Au NPs at a toluene/water interface with ethanol as the inducer is used for the forming of gold nanoparticles (Au NPs) monolayer. The organic memory devices exhibited good memory effects by hole trapping/detrapping in the gold nanoparticles. And also we design a modification of memory window by transfer times.

Effect of surface treatment of substrate on field emission characteristics of carbon nanotubes

The field emission characteristics of patterned carbon nanotubes whose average diameter is 16nm cathodes on substrates with surface treatment were investigated. The surface treatment of the substrate was performed by nickel electroless plating. Carbon nanotubes were patterned on the surface treated substrate with radius of 200μm through conventional photolithography process. It was revealed that the different surface morphologies of the substrates have influence on the field emission characteristics in this study. Through the surface treatment, the roughness of the surface increased and cathode with a high roughness factor showed better field emission characteristics compared to non-treated ones.