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Graphene and its related materials have attracted much interest in sensing applications because of their optimized ratio between active surface and bulk volume. In particular, several forms of oxidized graphene have been studied to optimize the sensing efficiency, sometimes moving away from practical solutions to boost performance. In this paper, we propose a practical, high-sensitivity, and easy to fabricate gas sensor based on high quality graphene oxide (GO), and we give the rationale to the high performance of the device. The device is fabricated by drop-casting water-dispersed single-layer GO flakes on standard 30 μm spaced interdigitated Pt electrodes. The exceptional size of the GO flakes (27 μm mean size and ∼500 μm maximum size) allows single GO flake to bridge adjacent electrodes. A typical p-type response is observed by testing the device in both reducing and oxidizing environments. The specific response to NO 2 is studied by varying the operating temperature and the gas concentration. Sensing activity is demonstrated to be mainly mediated by the oxygen functional groups. A 20 ppb detection limit is measured. Besides illustrating a simple and efficient approach to gas sensing, this work is an example of the versatility of graphene oxide, accomplishing tasks that are complementary to graphene.

Room temperature gas sensing properties of chemically exfoliated black phosphorus (BP) to oxidizing (NO 2 , CO 2 ) and reducing (NH 3 , H 2 , CO) gases in a dry air carrier have been reported. To study the gas sensing properties of BP, chemically exfoliated BP flakes have been drop casted on Si 3 N 4 substrates provided with Pt comb-type interdigitated electrodes in N 2 atmosphere. Scanning electron microscopy and x-ray photoelectron spectroscopy characterizations show respectively the occurrence of a mixed structure, composed of BP coarse aggregates dispersed on BP exfoliated few layer flakes bridging the electrodes, and a clear 2p doublet belonging to BP, which excludes the occurrence of surface oxidation. Room temperature electrical tests in dry air show a p-type response of multilayer BP with measured detection limits of 20 ppb and 10 ppm to NO 2 and NH 3 respectively. No response to CO and CO 2 has been detected, while a slight but steady sensitivity to H 2 has been recorded. The reported results confirm, on an experimental basis, what was previously theoretically predicted, demonstrating the promising sensing properties of exfoliated BP.

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