Metal-Ion-Intercalated MXene Nanosheet Films for NH₃ Gas Detection

Abstract

High conductivity and transparency and sheet-like two-dimensional morphology of MXenes make them attractive for use as functional transparent thin films. In addition, because of the dense surface functional groups and negative surface charge of the MXene sheet, cationic species can be easily intercalated into MXene interlayers to largely enhance the film properties and device performance. In this paper, for the first time, we demonstrate a spontaneous self-assembly method to efficiently intercalate metal ions into MXene transparent thin films with cation-dependent properties. Unlike in previous methods that intercalate ions after film assembly, monovalent and divalent metal ions are easily intercalated during the self-assembly process within a very short period of time. The optoelectronic properties are dependent on the intercalated cation where uniformly assembled ion-intercalated Ti3C2T x MXene thin films exhibited on average a high optical transmittance of ∼90% at a wavelength of 550 nm. The ion-intercalated MXene films were utilized as gas sensors to detect ammonia gas. Interestingly, metal-ion-intercalated films showed a much higher signal-to-noise ratio upon exposure to ammonia gas compared to that of films assembled without metal ions, demonstrating the positive influence of metal-ion intercalation on enhancing the gas-sensing performance.

A Family of 2D-MXenes: Synthesis, Properties, and Gas Sensing Applications

“…Kim et al fabricated uniform, transparent, metalion-intercalated Ti 3 C 2 T x MXene thin films via a self-assembly method and successfully transferred these fully assembled films onto polystyrene (PS), poly(vinyl chloride) (PVC), polyimide (PI), polypropylene (PP), and poly(vinylidene fluoride) (PVDF) polymer substrates as shown in Figure 10(iii), for further demonstrating their potential for application in flexible and wearable devices. 251 The thickness of the MXene film was effectively controlled by transferring multiple films onto a single substrate. MXene films can be easily transferred onto structured films such as the PP film, which is rather challenging to achieve by conventional coating methods because protruded structures can obstruct the fabrication of uniform films during the coating.…”

“…Furthermore, the fabricated flexible MXene sensors not only exhibited an outstanding room-temperature sensing response toward a variety of VOCs but also demonstrated outstanding durability ascribed to the mechanical and flexibility properties of the flexible sensor, which further broadens the potential applications of the Ti 3 C 2 T x -F sensor to wearable IoT. Kim et al fabricated uniform, transparent, metal-ion-intercalated Ti 3 C 2 T x MXene thin films via a self-assembly method and successfully transferred these fully assembled films onto polystyrene (PS), poly­(vinyl chloride) (PVC), polyimide (PI), polypropylene (PP), and poly­(vinylidene fluoride) (PVDF) polymer substrates as shown in Figure (iii), for further demonstrating their potential for application in flexible and wearable devices . The thickness of the MXene film was effectively controlled by transferring multiple films onto a single substrate.…”

“…(iii) Photographs of Mg-MXene thin films transferred onto various flexible substrates: polystyrene (PS), poly­(vinyl chloride) (PVC), polyimide (PI), polypropylene (PP), and poly­(vinylidene fluoride) (PVDF). Reprinted with permission from ref . Copyright 2021 American Chemical Society.…”

2D materials: increscent quantum flatland with immense potential for applications

“…The intercalation improved the signal-to-noise ratio to tenfold compared to pristine MXene. The sensing performance of Na, K, Mg, and Ca intercalated MXene was compared, out of which Na-MXene showed the highest response with LOD of 10 ppm due to low film thickness and high electrical resistance [ 98 ]. He et al developed a gas sensor based on MXene/SnO 2 heterojunction for ammonia sensing at RT.…”

“…c Response of the Ti 3 C 2 T x MXene/PANI/BC composite aerogel-based gas sensor to NH 3 gas for varied concentration ranges. [ 98 ] d Sensor current response profile with the UV-on of F-SnO 2 sensor [ 101 ] e fabrication process and design of the 2H-WSe 2 nanosheet sensor. f Dynamic response of 2H-WSe 2 (2D), 2H-WSe 2 (8D), and 2H-WSe 2 (12D) sensors at RT.…”