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Metal oxide nanoparticles, such as CuO and SnO 2 , are outstanding systems for H 2 S gas sensing in air. In this work, those nanoparticles were deposited with different mixing percentages on substrates to form percolating networks of nanoparticles. Electrical electrodes were deposited on the nanoparticles' films to investigate their gas sensing response against H 2 and H 2 S, and their electrical characteristics. The sensor devices based on CuO-SnO 2 nanoparticles revealed enhanced sensing characteristics against H 2 S with a sensitivity of 10 ppm. The enhanced sensing characteristics could be attributed to the formation of PN-junctions among CuO and SnO 2 nanoparticles. The reasonable production cost (due to simple structure and cheap used materials), low power consumption (~ 1 µW for H 2 S at room temperature), high sensitivity, high response, and reasonable response time of the present sensors qualify them for practical implementation in portable gas sensing devices with enhanced characteristics.

Titanium carbide (Ti3C2Tx) MXene possesses various unique physicochemical and catalytic properties.However, the electrochemical CO oxidation performance is not yet addressed experimentally. Herein, Ti3C2Tx (TX=OH, O, and F) ordered and exfoliated two-dimensional nanosheets ornamented with semispherical pallidum nanoparticles (2.5 Wt. %) with an average diameter of (10 ±1 nm) (denoted as Pd/Ti3C2Tx) is rationally designed for the electrochemical CO oxidation. The fabrication process is based on the selective chemical etching of Ti3AlC2 and delamination under sonication to form Ti3C2Tx nanosheets that are used as a substrate and reducing agent for supporting in situ growth of Pd nanoparticles via impregnation with Pd salt. Interestingly, Pd-free Ti3C2Tx displayed inferior CO oxidation activity, while Pd/Ti3C2Tx enhanced the CO oxidation activity substantially. This is attributed to the combination of outstanding physicochemical properties of Ti3C2Tx and the catalytic merits of Pd nanoparticles.

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