Mwcnts And Zno / Sno <sub> 2 </ Sub> Composites No Gas Sensing Research

In order to develop NO gas sensor working at room temperature, MWCNTs/porous ZnO composite was synthesized by homogeneous precipitation method, MWCNTs/SnO₂ composite was synthesized by SnCl₂ solution method, and MWCNTs/SnO₂/ZnO composite was synthesized by the combination of SnCl₂ solution method and homogeneous precipitation method. Their NO response properties were investigated at room temperature by static state injection method, and their response mechanism was discussed.In the MWCNTs/ZnO composite synthesized by homogeneous precipitation method, a homogeneous distribution of MWCNTs was observed while ZnO existed as porous nanosheets consisting of many ZnO nanoparticles. Room-temperature NO sensing test showed that the response of MWCNTs/ZnO composite toward NO was much higher than that of MWCNTs or ZnO. The MWCNTs/ZnO sensor′s response has increased by a factor of three in comparison with that of MWCNT-COOH toward 100×10^-6 NO, while ZnO showed no response to 100×10^-6 NO at room temperature. The unique sensor response of MWCNTs/ZnO composite can be attributed to two factors: the large surface area and the electron transfer from p-type MWCNTs to ZnO when NO molecules were adsorbed on the composite.In the MWCNTs/SnO₂ composite synthesized by SnCl₂ solution method, SnO₂ nanoparticles of only 5 nm were deposited uniformly on the surface of MWCNTs. The weight ratio of MWCNTs to SnO₂ in the composite was kept 3:1. Room-temperature NO sensing test showed that the MWCNTs/SnO₂ sensor′s response has increased by a factor of four in comparison with that of MWCNTs toward 100×10^-6 NO. Therefore, modification of SnO₂ nanoparticles could improve significantly the response of MWCNTs toward NO at room temperature. This was because the electrons transferred from p-type MWCNTs to SnO₂ when NO molecules were adsorbed on the MWCNTs/SnO₂ composite.MWCNTs/SnO₂/ZnO composite was synthesized by introduction of ZnO to MWCNTs/SnO₂ composite through homogeneous precipitation method. Room-temperature NO sensing test showed that the MWCNTs/SnO₂/ZnO sensor′s response has increased by a factor of two in comparison with that of MWCNTs/SnO₂ toward 100×10^-6 NO, and the response time and recovery time was shortened by 1/2 and 2/3. The unique response property of MWCNTs/SnO₂/ZnO composite can be attributed to the interaction between SnO₂ and ZnO.This article reveals that the combination of MWCNTs and metal oxides can improve the room-temperature NO response of MWCNTs, and MWCNTs/metal oxide composite is a very promising gas sensor material that can work at room temperature.