Gas Sensors Based On One-Dimensional Nanomaterials And The Studies Of Their Applications

In this dissertation,the sensing properties of two kinds of one-dimentional(1D) nanomaterials(ZnO nanorods and carbon nanotubes) have been investigated.The gas sensors based on carbon nanotubes have been applied to detect drugs and explosives. The main contents can be briefly described as follows:(1) The ionization gas sensors based on ZnO nanorods have been introduced including their fabrication methods and the structure and operation method of their measurement system.The different measurement methods have been campared including breakdown voltage vs.prebreakdown current measurement and static vs. dynamic measurement of prebreakdown current.The sensing properties of the ZnO based ionization sensor to VOCs(for example,acetic acid and acetone) have been studied by the dynamic prebreakdown current measurement.It has been discussed in detail about the influence factors of the dynamic measurement.In addition,the anti-oxidation performances of carbon nanotubes as ionization tips have been indicated by experiment.(2) Exploiting the properties of field ionization,polarization and adsorption of carbon nanotubes,four kinds of novel gas sensors have been fabricated as follows: Metal electrodes were prepared on two sides of a SiO₂/Si wafer by screen printing, which constituted a flat capacitor.MWCNTs were synthesized on the top electrode by chemical vapor deposition.So,a capacitive gas sensor based on MWCNT film brought to success,in which MWCNTs act as the sensing matrials;SWCNTs were synthesized on a SiO₂/Si wafer in advance,and then interdigited electrodes were fabricated onto the SWCNT film by MEMS process.Then,a capacitive/conductive gas sensor based on SWCNTs brought to success;SnO₂ nano-particles were modified onto the sufaces of MWCNTs by wet-chemical technique,which were used to fabricated a conductive gas sensor;Vertically aligned MWCNT arrays were synthesized by acetone pyrolysis in anodized aluminum oxide(AAO) templates.After a series of processes,two Si wafers were pasted to the MWCNTs terminals on the top and bottom surfaces of the AAO template.Then,the AAO was etched by HF acid and a capacitive gas sensor based on MWCNT arrays was accomplished.The sensing properties of those carbon nanotube based gas sensors have been systemically investigated.(3) Three kinds of gas sensors were arrayed by e-nose technology including the conductive gas sensor based on SnO₂ nano-particles modified MWCNTs,a SnO₂ gas sensor and the capacitive gas sensor based on MWCNT film.The sensing properties of the arrays to drugs and explosives were investigated and a prototype was furtherly developed which have many advantages such as small bulk,small weight,fast response,reliable working and so on.