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NOVEL ZINC OXIDE FUNCTIONALIZED CARBON NANOTUBE CHEMIRESISTOR SENSOR ENHANCED WITH SURFACE O2 PLASMA INDUCED DEFECTS FOR METHANEDETECTION AT SINGLE PPM LEVEL
Citation:
Humayun, T., I. Paprotny, R. Divan, L. Stan, L. Gundel, AND P. Solomon. NOVEL ZINC OXIDE FUNCTIONALIZED CARBON NANOTUBE CHEMIRESISTOR SENSOR ENHANCED WITH SURFACE O2 PLASMA INDUCED DEFECTS FOR METHANEDETECTION AT SINGLE PPM LEVEL. 18th International Conference on Solid-State Sensors, Actuators and Microsystems Transduers 2015, Anchorage, AK, June 21 - 25, 2015.
Impact/Purpose:
The National Exposure Research Laboratory (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA mission to protect human health and the environment. HEASD research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Description:
Novelty/Progress ClaimsThis paper presents a novel functionalized multi-walled carbon nanotubes (MWCNTs) based chemiresistor sensor which can detect methane at 2 ppm concentration level at room temperature with relative resistance change (RRC) of 2%. This is the highest reported sensitivity for CNT chemristorbased methane sensors to this date. The observed change in sensitivity (2x larger at three times lower ppm) comparing to the previously reported functionalized CNT chemiresistors is a result of implementing ZnO atomic layer deposition (ALD)functionalization with novel O2 plasma pretreatmentof the CNTs to induce surface defects,enhancing ZnO affinity.Background/State-of-the-artMetal-oxide based sensors are commonly used to sense methane (CH4), however continuous heating is necessary to initiate the surface chemisorption ofoxygen, often requiring 100s of mWs of power [1]. In contrast, it has been shown that CNT-based methane ensors can detect ppm levels of CH4 at room temperature, with power consumption of only few mWs [1], [4], [5]. Previously reported CNT-based CH4sensors with maximum relative resistance change of 1% (at 6 ppm CH4) use Pd as the functionalizing material [1]. Pd is not only an expensive metal to use forfunctionalization of CNTs, but it also forms a significant Schottky barrier with bare CNT [2]. Furthermore, the chemically inert graphitic surface of bare CNTs creates a relatively poor bond with the functionalization compound. Consequently, surface pre-treatment of CNTs is necessary to achieve highly sensitive CNT chemiresistor-based sensors. The surface pre-treatment must be such as not to disturb the morphology of the CNTs.
