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Open AccessArticle

Near Room Temperature Light-Activated WS2-Decorated rGO as NO2 Gas Sensor

1
Department of Industrial and Information Engineering and Economics, Via G. Gronchi 18, University of L’Aquila, I-67100 L’Aquila, Italy
2
Department of Physical and Chemical Sciences, Via Vetoio 10, University of L’Aquila, I-67100 L’Aquila, Italy
3
CNR-SPIN Uos L’Aquila, Via Vetoio 10, I-67100 L’Aquila, Italy
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(11), 2617; https://doi.org/10.3390/s19112617
Received: 10 May 2019 / Revised: 2 June 2019 / Accepted: 6 June 2019 / Published: 9 June 2019
(This article belongs to the Special Issue Applications of Graphene-Based Materials in Sensors)
The NO2 response in the range of 200 ppb to 1 ppm of a chemoresistive WS2-decorated rGO sensor has been investigated at operating temperatures of 25 °C and 50 °C in dry and humid air (40% RH) under dark and Purple Blue (PB) light conditions (λ = 430 nm). Few-layers WS2, exfoliated by ball milling and sonication technique, with average dimensions of 200 nm, have been mixed with rGO flakes (average dimension 700 nm) to yield WS2-decorated rGO, deposited on Si3N4 substrates, provided with platinum (30 μm gap distance) finger-type electrodes. TEM analysis showed the formation of homogeneous and well-dispersed WS2 flakes distributed over a thin, continuous and uniform underlying layer of interconnected rGO flakes. XPS and STEM revealed a partial oxidation of WS2 flakes leading to the formation of 18% amorphous WO3 over the WS2 flakes. PB-light irradiation and mild heating of the sensor at 50 °C substantially enhanced the baseline recovery yielding improved adsorption/desorption rates, with detection limit of 400 ppb NO2 and reproducible gas responses. Cross sensitivity tests with humid air interfering vapor highlighted a negligible influence of water vapor on the NO2 response. A charge carrier mechanism between WS2 and rGO is proposed and discussed to explain the overall NO2 and H2O response of the WS2–rGO hybrids. View Full-Text
Keywords: WS2–rGO hybrids; chemoresistive sensors; NO2; Purple Blue light activation WS2–rGO hybrids; chemoresistive sensors; NO2; Purple Blue light activation
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Paolucci, V.; Emamjomeh, S.M.; Ottaviano, L.; Cantalini, C. Near Room Temperature Light-Activated WS2-Decorated rGO as NO2 Gas Sensor. Sensors 2019, 19, 2617.

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