ZnO Carbon Nanotubes Research Articles

NO Gas Sensing Characteristics of Layered Composites of Carbon Nanotubes Coated with Al-doped ZnO

We investigated the NO gas sensing characteristics of ZnO-carbon nanotube (ZnO-CNT) layered composites fabricated by coaxial coating of single-walled CNTs with a thin layer of 1 wt% Al-doped ZnO using rf magnetron sputtering deposition. Morphological studies clearly revealed that the ZnO appeared to form beadshaped crystalline nanoparticles with an average diameter as small as 30 nm, attaching to the surface of the nanotubes. It was found that the NO gas sensing properties of the ZnO-CNT layered composites were dramatically improved over Al-doped ZnO thin films. It is reasoned from these observations that an increase in the surface-to-volume ratio associated with the numerous ZnO “nanobeads” on the surface of the CNTs results in the enhancement of the NO gas sensing properties. The ZnO-CNT layered composite sensors exhibited a maximum sensitivity of 13.7 to 2 ppm NO gas at a temperature of 200 and a low NO gas detection limit of 0.2 ppm in dry air.

NO Gas Sensing Properties of ZnO-Carbon Nanotube Composites

Abstract The NO gas sensing properties of ZnO-carbon nanotube (ZnO-CNT) composites fabricated by thecoaxial coating of single-walled CNTs with ZnO were investigated using pulsed laser deposition. Uponexamination, the morphology and crystallinity of the ZnO-CNT composites showed that CNTs were uniformlycoated with polycrystalline ZnO with a grain size as small as 5-10 nm. Gas sensing measurements clearlyindicated a remarkable enhancement of the sensitivity of ZnO-CNT composites for NO gas compared to thatof ZnO films while maintaining the strong sensing stability of the composites, properties that CNT-basedsensing materials do not have. The enhanced gas sensing properties of the ZnO-CNT composites are attributedto an increase in the surface adsorption area of the ZnO layer via the coating by CNTs of a high surface-to-volume ratio structure. These results suggest that the ZnO-CNT composite is a promising template for novelsolid-state semiconducting gas sensors.Key words ZnO gas sensor, carbon nanotube, ZnO-CNT composite

Synthesis and field electron emission properties of hybrid carbon nanotubes andnanoparticles

Hybrid ZnO–carbon nanotubes as well as nanodiamond–carbon nanotubes weresynthesized via a straightforward process of plasma enhanced chemical vapordeposition. For the former, ZnO nanoparticles were instantly coated on the tubesurface in the final growing process of carbon nanotubes, while for the latterdiamond nanoparticles were grown using pretreatment of a silicon substrate withNi(NO3)2·6H2O/Mg(NO3)2·6H2O alcohol solution prior to deposition and a highH2/CH4 gas flow ratio in the deposition process. The morphology and microstructure of theobtained hybrid materials were characterized by transmission electron microscopy. Bothhybrid ZnO–carbon nanotubes and nanodiamond–carbon nanotubes exhibited excellentfield emission properties.

Fabrication of Three-Dimensional ZnO−Carbon Nanotube (CNT) Hybrids Using Self-Assembled CNT Micropatterns as Framework

Large-scale pyramid-like micropatterns were prepared via capillarity-driven self-assembly during the evaporation of water from aligned carbon nanotubes (ACNTs) wrapped by a polyelectrolyte, poly (sodium 4-styrenesulfonate) (PSS). PSS wrapping results in providing negative charges on every tube, which makes it possible to balance the capillary force and to form uniformed pyramid-like architecture. By using such regular three-dimensional CNT patterns as an idea candidate for the framework/template, two complex architectures consisting of ZnO nanorods and CNT patterns were successfully fabricated, which show revisable surface wettability properties.

Negative photoconduction of planar heterogeneous random network of ZnO-carbon nanotubes

In this letter, the authors report on the effect of negative photoconduction observed in heterogeneous two-dimensional random networks comprising single-walled nanotubes and ZnO particles, and investigated by room temperature dc-photoconduction measurements. For this, two-terminal thin film devices engineered by solution coating of the nanotubes with ZnO microparticles consistently exhibited increase in the resistance versus decrease in the nanotubes alone with ultraviolet illumination, which is explained within the model of interface-mediated charging/discharging effects. The study suggests the possibility of engineering reduced-cost and multirange nanotube light sensors based on extrinsic carrier modulation via external gating at the interface.

Water‐Assisted Growth of Aligned Carbon Nanotube–ZnO Heterojunction Arrays

Using water-assisted chemical vapor deposition, aligned CNT–ZnO (CNT: carbon nanotube) heterojunctions are formed on a Zn substrate. The aligned CNT heterojunctions with intimately connected ZnO particles/rods show interesting optoelectronic properties of practical significance. This cost-effective and efficient approach can be scaled up for the production of large-area heterojunction arrays (see figure).