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Lookup NU author(s): Atsinafe Oshido,
Professor Andrew HoultonORCiD,
Dr Ben Horrocks
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Electronic sensors for volatile organic compounds have been prepared by drop-casting dispersionsof multi-wall carbon nanotubes (MWCNTs) in aqueous solutions of λ-DNA onto Pt microbandelectrodes. The MWCNTs themselves show a metal-like temperature dependence of theconductance, but the conductance of DNA/MWCNT composites has an activated component thatcorresponds to inter-tube tunneling. The resistance of the composite was modelled by a seriescombination of a term linear in temperature for the nanotubes and a stretched exponential form forthe inter-tube junctions. The resistance may increase or decrease with temperature according to thecomposition and may be tuned to be almost temperature-independent at 67% by mass of DNA.Upon exposure to organic vapours, the resistance of the composites increases and the time-dependence of this signal is consistent with diffusion of the vapour into the composite. Thefractional change in resistance at steady-state provides an analytical signal with a linear calibrationand the presence of DNA enhances the signal and adjusts the selectivity in favour of polar analytes.The temperature dependence of the signal is determined by the enthalpy of adsorption of theanalyte in the inter-tube junctions and may be satisfactorily modelled using the Langmuir isotherm.Temperature and pressure-dependent studies indicate that neither charge injection by oxidation/reduction of the analyte nor condensation of analyte on the device is responsible for the signal. Wesuggest that the origin of the sensing response is an adsorption of the analyte in the inter-tuberegions that modulates the tunneling barriers. This suggests a general route to tuning the selectivityof MWCNT gas sensors using non-conductive polymers of varying chemical functionality.
Author(s): Ali SB, Oshido AB, Houlton A, Horrocks BR
Publication type: Article
Publication status: Published
Online publication date: 08/11/2021
Acceptance date: 08/10/2021
Date deposited: 06/04/2022
ISSN (print): 0957-4484
ISSN (electronic): 1361-6528
Publisher: Institute of Physics Publishing Ltd.
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