The Study Of Toxic Gas Sensors Based On Carbon Nanotube Sensitive Film

Carbon nanotube is an ideal one dimension nano material. It has a high ratio of surface proportion and excellent electronic property, which makes it a very suitable sensing material for gas sensor. Gas sensors with different functional groups grafted on MWCNTs are studied to detect indoor harmful gas such as formaldehyde, toluene and to improve sensor responses.The MWCNTs gas sensor grafted by ethylene diamine to detect formaldehyde was first studied. To fabricate the sensor, oxided the MWCNTs with H2SO4/HON3first, then rectected the products with ethylene diamine, dispersed the functionalized MWCNTs in Nafion/normal propyl alcohol solution, dropped coating the solution on Interdigital electrode, and finally the sensitive films was obtained. MWCNTs was characterized by SEM, FTIR, also the grafting rate of ethylene diamine was got by nitrogen element analysis method. The sensitive films based on pure MWCNTs,5.55%and18.19%grafting rate MWCNTs were selected to detect the formaldehyde with the concentration of20ppb,50ppb,80ppb,120ppb and200ppb. The results showed that the response of grafted MWCNTs to formaldehyde improved greatly. The sensitivity of MWCNTs with18.19%grafting rate to formaldehyde was13times more than pure MWCNTs when the concentration is at20ppb. The reason why response improved was discussed in the paper. The selectivity of the sensitive film with18.19%grafting rate was studied by comparing its response to formaldehyde with other gases such as ethanol. ethanol, acetone, NH3and CO2with the concentration of200ppb, and the result showed good selectivity. The repeatability of the gas sensor was also studied by repeating the adsorption-desorption process3times when the concentration of formaldehyde was50ppb and showed good behavior of the repeatability.The gas sensors based on MWCNTs grafted by benzylamine and lauryl amine were also fabricated to detect toluene. The MWCNTs with pure and grafted by benzylamine and lauryl amine were used to detect toluene with the concentration of100ppb,200ppb,300ppb, and400ppb. The results showed that the sensitivity of sensitive films grafted by benzylamine and lauryl amine was5and3times more than ungrafted respectively.The paper’s research demonstrateed that chemical grafting is an effective method to improve the performance of gas sensor based on CNTs. All research results will provide experimental basis for the practical study of gas sensor.