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Functionalized carbon nanotubes as sensitive layers for BTEX sensing


The BTEX (benzene, toluene, ethylbenzene and xylene) volatile organic compounds constitute an important class of indoor air pollutants. Human exposure to these compounds can cause serious damages on human health due to their carcinogenic nature. Therefore, it is a priority to detect such pollutants. Carbon nanotubes (CNTs) have received considerable interest over the last decade as new sensing materials due to their high specific surface area and their electronic properties. For instance, several groups have already demonstrated their outstanding abilities by studying the changes of CNT electrical properties upon gas exposure1,2,3. In this context, the objective of our work is to develop chemical sensors based on carbon nanotubes to detect BTEX compounds and especially benzene and toluene. Carbon nanotubes used for sensing devices are synthesized using catalytic chemical vapour deposition (CCVD) process4, which provides multi-walled carbon nanotubes (MWCNTs) with an outer diameter around 40 nm. The raw MWCNTs are then annealed at 2000°C under argon atmosphere and, eventually, functionalized to increase sensing selectivity. In this study, the detection performances of simply annealed CNT and functionalized ones are both studied. Hence, functional groups with a high affinity towards the selected target, i.e. benzene or toluene, were grafted at the surface. First, as carboxylic groups are known for BTEX adsorption by π-π stacking interactions (Figure 1.A)5, a simple acid treatment with HCl and HNO3 was performed to obtain –COOH groups on the surface. Second, in order to increase beneficial interactions with BTEX, several poly(phenylene) coatings bearing carboxylic groups were investigated for BTEX detection (Figure 1.B). The principle is based on BTEX interaction by π-π stacking with the aromatics and carboxylic groups of the coating. The functionalisation process with poly(phenylene) coatings is derived from the diazonium salt chemistry6. 4-carboxyphenyldiazonium chloride was synthesized in situ from the 4-aminobenzoic acid and sodium nitrite. The synthesis was performed in HCl solution and ascorbic acid was used as reducing agent. Such coatings were characterized on gold substrates and on CNT by XPS, FTIR and contact angle measurements. First tests demonstrate that simply annealed CNT–based sensors are able to detect benzene at concentrations in the tenth of ppb range which is appropriate for indoor air qualification. The functionalized CNT-based sensors are now to be compared to annealed CNT-based sensors in order to determine their performance ability
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cea-02346082 , version 1 (04-11-2019)


  • HAL Id : cea-02346082 , version 1


Adeline Trouvé, Guy Deniau, Dominique Porterat, Jocelyne Leroy, Serge Palacin, et al.. Functionalized carbon nanotubes as sensitive layers for BTEX sensing. ChemOnTubes2016, Apr 2016, Brussels, Belgium. ⟨cea-02346082⟩
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