MXenes,
two-dimensional transition metal carbides or nitrides,
have recently shown great promise for gas sensing applications. We
demonstrate that the sensitivity of intrinsically metallic Ti3C2T
x
MXene can be considerably
improved via its partial oxidation in air at 350 °C. The annealed
films of MXene sheets remain electrically conductive, while their
decoration with semiconducting TiO2 considerably improves
their chemiresistive response to organic analytes at low-ppm concentrations
in dry air, which was used to emulate practical sensing environments.
We demonstrate that partially oxidized MXene has a faster and a qualitatively
different sensor response to volatile analytes compared to pristine
Ti3C2T
x
. We fabricated
multisensor arrays of partially oxidized Ti3C2T
x
MXene devices and demonstrate that
in addition to their high sensitivity they enable a selective recognition
of analytes of nearly the same chemical nature, such as low molecular
weight alcohols. We investigated the oxidation behavior of Ti3C2T
x
in air in a wide
temperature range and discuss the mechanism of sensor response of
partially oxidized MXene films, which is qualitatively different from
that of pristine Ti3C2T
x
.
We report a deposition of the tin oxide/hydroxide nanostructured layer by the potentiodynamic method from acidic nitrate solutions directly over the substrate, equipped with multiple strip electrodes which is employed as a gas-analytical multisensor array chip. The electrochemical synthesis is set to favor the growth of the tin oxide/hydroxide phase, while the appearance of metallic Sn is suppressed by cycling. The as-synthesized tin oxide/hydroxide layer is characterized by mesoporous morphology with grains, 250–300 nm diameter, which are further crystallized into fine SnO2 poly-nanocrystals following heating to 300 °C for 24 h just on the chip. The fabricated layer exhibits chemiresistive properties under exposure to organic vapors, which allows the generation of a multisensor vector signal capable of selectively distinguishing various vapors.
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