High sensitivity carbon nanotubes flow-rate sensors and their performance improvement by coating

Highly Sensitive Hot-Wire Anemometry Based on Macro-Sized Double-Walled Carbon Nanotube Strands

This paper presents a highly sensitive flow-rate sensor with carbon nanotubes (CNTs) as sensing elements. The sensor uses micro-size centimeters long double-walled CNT (DWCNT) strands as hot-wires to sense fluid velocity. In the theoretical analysis, the sensitivity of the sensor is demonstrated to be positively related to the ratio of its surface. We assemble the flow sensor by suspending the DWCNT strand directly on two tungsten prongs and dripping a small amount of silver glue onto each contact between the DWCNT and the prongs. The DWCNT exhibits a positive TCR of 1980 ppm/K. The self-heating effect on the DWCNT was observed while constant current was applied between the two prongs. This sensor can evidently respond to flow rate, and requires only several milliwatts to operate. We have, thus far, demonstrated that the CNT-based flow sensor has better sensitivity than the Pt-coated DWCNT sensor.

Single-walled carbon nanotubes coated with ZnO by atomic layer deposition

The possibility of ZnO deposition on the surface of single-walled carbon nanotubes (SWCNTs) with the help of an atomic layer deposition (ALD) technique was successfully demonstrated. The utilization of pristine SWCNTs as a support resulted in a non-uniform deposition of ZnO in the form of nanoparticles. To achieve uniform ZnO coating, the SWCNTs first needed to be functionalized by treating the samples in a controlled ozone atmosphere. The uniformly ZnO coated SWCNTs were used to fabricate UV sensing devices. An UV irradiation of the ZnO coated samples turned them from hydrophobic to hydrophilic behaviour. Furthermore, thin films of the ZnO coated SWCNTs allowed us switch p-type field effect transistors made of pristine SWCNTs to have ambipolar characteristics.

Analytical modeling of the sensing parameters for graphene nanoscroll-based gas sensors

The current–voltage (I–V) model for a GNS-based gas sensor (like the FET-based structure) has been investigated under exposure to different NH₃ gas concentrations at different temperatures.

First-principles study of ZnO cluster-decorated carbon nanotubes

We have investigated the structural, electronic and carbon monoxide (CO) detection properties of the ZnO cluster-decorated single-walled carbon nanotubes (SWCNTs) by using density functional theory (DFT). The stable structures of hybrid ZnO/SWCNT materials are that the ZnO cluster plane is perpendicular to the surface of SWCNTs with the Zn atoms towards the SWCNTs (Zn atom above axial C-C bond or above the C atom). For the ZnO cluster-decorated semiconducting SWCNTs, the SWCNTs present p-type characteristics which may lead to the decrease of conductance upon illumination with ultraviolet (UV) light. The CO can be adsorbed on the hybrid ZnO/SWCNT materials due to the charge transfer between them. Compared with isolated ZnO clusters or bare SWCNTs, the ZnO/SWCNT network would have excellent CO detection ability due to their suitable adsorption energy and conductivity.