Title

Metal-decorated carbon nanotubes for gas sensing applications

Abstract

This thesis reports on the investigation of metal-decorated carbon nanotubes-based sensor arrays with enhanced sensitivity and selectivity toward toxic gases. Ab initio first-principles methods were used to expedite the process of identifying the right materials with the highest potential compared to in-lab trial and error as well as to provide a deeper understanding of the gas adsorption mechanism. The mechanism of NO2 adsorption on Cu-, Pt- and Ti-doped single-walled carbon nanotubes (SWCNTs) was investigated. Modelling the isolated NO2 molecule indicated the formation of a band gap between the 3π* HOMO and 5σ* LUMO levels, which were found to be the electronic states primarily involved in the bonding process. Metal doping decreased the system stability and altered the SWCNT structure. NO2 exposure caused the transfer of electrons to the gas molecules, thereby enhancing the p-type conductivity of the M-SWCNT structure. The highest charge transfer to the NO2 molecule was observed for Ti-SWCNTs (0.456 eV), while the lowest was found for Cu-SWCNTs (0.351 eV). Ti-SWCNTs exhibited the highest stability and sensitivity as a potential NO2 gas sensing material out of the 3 investigated metal dopants. The DFT predictions were verified with the experimental results. The experimental results of these Ti-, Pt-, and Cu-decorated CNTs when exposed to NO2 were found to have the same order as predicted by DFT calculations. The sensors were the fabricated using a Kapton base with a printed gold circuit and silver electrodes to decrease current losses between contacts. The synthesized material was tested upon exposure to four toxic gases; NO2, H2S, NH3 and CO. Although CO showed the weakest resistance change among the other gases, its highest resistance change was found for exposed to Ag and pristine CNTs. Cu-decorated CNTs showed the highest response to H2S out of the tested metal decorated sensors. NH3 showed a good response to Ru-decorated CNTs. The different responses generated by each of the metal dopants under the exposure of each gas generated a unique response pattern that can be used as an identifier.

Department

Environmental Engineering Program

Date of Award

2-1-2020

Online Submission Date

September 2019

First Advisor

Allam, Nageh

Committee Member 1

ElGendy, Ahmed

Committee Member 2

Hamed, Ahmed

Document Type

Dissertation

Extent

157 p.

Rights

The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy.

IRB

Approval has been obtained for this item

Comments

Youssef Jameel Foundation

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