Solid organic acid tetrafluorohydroquinone functionalized single-walled carbon nanotube chemiresistive sensors for highly sensitive and selective formaldehyde detection

Single-walled carbon nanotubes (SWNTs) are ideal candidates as active elements for fabricating gas sensors because their electronic structures are easily disrupted by the binding of analytes, but the utilization of SWNT sensors to detect formaldehyde is limited, mainly because of a weak physical adsorption between SWNTs and formaldehyde. Herein we developed a chemiresistive sensor based on tetrafluorohydroquinone (TFQ) functionalized semiconducting SWNT networks for highly sensitive and rapid detection of formaldehyde vapor. The SWNT network was deposited between interdigitated electrodes and modified by solid organic acid TFQ. The interaction of formaldehyde with TFQ on the surface of SWNTs caused significant increase in the conductance of the SWNT sensors, and enabled the sensors to easily detect formaldehyde at parts-per-billion (ppb) concentration level with the response time of less than 1 min, without the need of pre-concentration of the analytes. The functionalized sensors also show excellent selectivity toward formaldehyde over those interfering organic vapors. This sensor could also be recovered when formaldehyde was replaced with referencing gas. The response mechanism was investigated.