Application of Titanium Carbide MXenes in Chemiresistive Gas Sensors

Abstract

The titanium carbide MXenes currently attract an extreme amount of interest from the material science community due to their promising functional properties arising from the two-dimensionality of these layered structures. In particular, the interaction between MXene and gaseous molecules, even at the physisorption level, yields a substantial shift in electrical parameters, which makes it possible to design gas sensors working at RT as a prerequisite to low-powered detection units. Herein, we consider to review such sensors, primarily based on Ti3C2Tx and Ti2CTx crystals as the most studied ones to date, delivering a chemiresistive type of signal. We analyze the ways reported in the literature to modify these 2D nanomaterials for (i) detecting various analyte gases, (ii) improving stability and sensitivity, (iii) reducing response/recovery times, and (iv) advancing a sensitivity to atmospheric humidity. The most powerful approach based on designing hetero-layers of MXenes with other crystals is discussed with regard to employing semiconductor metal oxides and chalcogenides, noble metal nanoparticles, carbon materials (graphene and nanotubes), and polymeric components. The current concepts on the detection mechanisms of MXenes and their hetero-composites are considered, and the background reasons for improving gas-sensing functionality in the hetero-composite when compared with pristine MXenes are classified. We formulate state-of-the-art advances and challenges in the field while proposing some possible solutions, in particular via employing a multisensor array paradigm.

Flexible humidity sensor based on PEDOT:PSS/Mxene nanocomposite

“…Secondly, swelling and increased interlayer distance in humid conditions elevate sensor resistance due to hindered electron hopping between PEDOT chains and altered electronic structure of MXene [62-65]. Thirdly, hydrogen bonding and electrostatic interactions between the hydrophilic surfaces of MXene/PEDOT:PSS and water molecules contribute to sensor sensitivity and selectivity causing significant changes in resistance based on water concentration [35]. The synergistic effect of PEDOT:PSS/MXene nanocomposite can enhance the humidity sensing at room temperature.…”

“…The MXene presents the attractive properties of excellent electroconductivity, rich surface chemistry and high aspect ratio [21,22]. According to these properties, the MXene has been widely used in sensor applications such as biosensor, pressure sensor, strain sensor and volatile organic compounds/gases sensors [23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Additionally, the sensing performance of MXene depends on its surface functional groups.…”

Current Trends and Promising Electrode Materials in Micro-Supercapacitor Printing

“…), X is C or N, and T is the surface functional groups, most commonly F, OH, Cl [ 161 , 162 ]. Due to their layered structure, high electrical conductivity, and huge variation in composition (which allows its optimization for a specific task), MXenes are recognized as very promising component base for various modern devices, e.g., in sensorics [ 163 , 164 , 165 , 166 , 167 ], catalysis [ 168 , 169 ], industrial water purification [ 170 , 171 ], and the creation of electrodes that often retain high energy density at high current densities [ 172 ]. However, they are of the greatest interest as components of energy generation and storage devices—lithium/sodium-ion batteries and supercapacitors [ 173 , 174 , 175 , 176 , 177 ]—especially owing to the possibility of intercalation of various ions into the interlayer space and high hydrophilicity of surface groups.…”

Nanochitin/MXene Composite Coated on Quartz Crystal Microbalance for Humidity Sensing

“…Furthermore, the loss of surface functional groups during synthesis or environmental exposure diminishes electrostatic repulsion, promoting stacking behavior. Coupled with the strong van der Waals forces, self-stacking phenomena are prone to occur [31][32][33], which limits the contact between internal active sites and water molecules. Chitin, derived from crab and shrimp shells, is a natural polysaccharide and the second most abundant biopolymer on Earth [34].…”