Partially Oxidized Ti3C2Tx MXenes for Fast and Selective Detection of Organic Vapors at Part-per-Million Concentrations

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 Ti3C2Tx MXene can be considerably improved via its partial oxidation in air at 350 degrees 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 Ti3C2Tx We fabricated multisensor arrays of partially oxidized Ti3C2Tx 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 Ti3C2Tx 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 Ti3C2Tx.