Emerging MXene-Polymer Hybrid Nanocomposites for High-Performance Ammonia Sensing and Monitoring

Abstract

Ammonia (NH₃) is a vital compound in diversified fields, including agriculture, automotive, chemical, food processing, hydrogen production and storage, and biomedical applications. Its extensive industrial use and emission have emerged hazardous to the ecosystem and have raised global public health concerns for monitoring NH₃ emissions and implementing proper safety strategies. These facts created emergent demand for translational and sustainable approaches to design efficient, affordable, and high-performance compact NH₃ sensors. Commercially available NH₃ sensors possess three major bottlenecks: poor selectivity, low concentration detection, and room-temperature operation. State-of-the-art NH₃ sensors are scaling up using advanced nano-systems possessing rapid, selective, efficient, and enhanced detection to overcome these challenges. MXene-polymer nanocomposites (MXP-NCs) are emerging as advanced nanomaterials of choice for NH₃ sensing owing to their affordability, excellent conductivity, mechanical flexibility, scalable production, rich surface functionalities, and tunable morphology. The MXP-NCs have demonstrated high performance to develop next-generation intelligent NH₃ sensors in agricultural, industrial, and biomedical applications. However, their excellent NH₃-sensing features are not articulated in the form of a review. This comprehensive review summarizes state-of-the-art MXP-NCs fabrication techniques, optimization of desired properties, enhanced sensing characteristics, and applications to detect airborne NH₃. Furthermore, an overview of challenges, possible solutions, and prospects associated with MXP-NCs is discussed.

Keywords: MXene–polymer nanocomposite; ammonia sensing; environmental monitoring; health wellness; intelligent sensing device.

Figure 1

Schematic of state-of-the-art NH₃ sensing techniques using different sensing signals.

Figure 2

Schematic of various ammonia sensing techniques using different sensing signals.

Figure 3

Statistics on yearly publication in the field of MXene–polymer nanocomposites (especially properties and processing of NCs). Reprinted from ref. [38].

Figure 4

Possible interactions in polymer nanocomposites. Reprinted with permission from ref. [46]. Copyright 2015 American Chemical Society.

Figure 5

Schematic of fabrication of MXene using selective Etching of MAX phase through wet and dry route.

Figure 6

Schematic of synthesis routes for MXP-NCs. Ex situ route: (a) blending, (b) alternate deposition. In situ route: (c) in situ polymerization.

Figure 7

Different reported strategies for fabrication of an ammonia-sensing device using MXP-NCs.

Figure 8

Morphological, structural, and chemical element analysis of PAN/Ti₃C₂T_x NC with (a) Morphology of Pristine Ti₃C₂T_x, (b,c) Morphology of PAN/Ti₃C₂T_x NC, (d) Structure of PAN/Ti₃C₂T_x NC through XRD Analysis, (e,f) XPS of PANI and PAN/Ti₃C₂T_x NC for chemical element analysis. Reprinted with permission from ref. [52] Copyright 2020 Elsevier.

Figure 9

Comparative TGA analysis of MXP-NC with its precursors in (a) argon atmosphere, and (b) ambient Atmosphere. Reprinted with permission from ref. [65]. Copyright 2020 American Chemical Society.

Figure 10

Hoping of charge carrier along 1D in conducting polymers due to addition of inorganic nanomaterials.

Figure 11

Schematic of ammonia sensing set-up. Reprinted with permission from ref. [69]. Copyright 2021 Wiley.

Figure 12

Chemisorption of ammonia in Ti₃C₂T_x/PEDOT: PSS sensors: Reprinted with permission ref. [65]. Copyright 2020 American Chemical Society.

Figure 13

Ammonia-sensing mechanism in p–p-type MXP-NCs due to formation of Schottky barrier.

Figure 14

Ammonia-sensing mechanism in p–n-type MXP-NCs due to formation of p–n junctions.

Figure 15

Flexibility of PEDOT: PSS/Ti₃C₂T_x NC ammonia sensor under different bending angles. Reprinted with permission from ref. [65]. Copyright 2020 American Chemical Society.

Figure 16

Ammonia-sensing in high humidity conditions. Reprinted with permission from ref. [56] Copyright 2021 Elsevier.

Figure 17

(a) Schematic of human breath analysis simulator, (b) monitoring of ammonia in exhaled human breath using MXP-NCs. Reprinted with permission from ref. [57]. Copyright 2021 Elsevi.er.

Figure 18

(a-c) Set-up to monitoring the volatilization of ammonia using MXP-NCs and (d) comparison of MXP-NCs performance in detecting volatilizing ammonia with results from DTM and SAAM techniques. Reprinted with permission from ref. [52]. Copyright 2020 Elsevier.

Figure 19

(A) Schematic of TENG coupled Nb₂CT_x/PAN ammonia sensor and (B) External load voltage as sensing parameter for (a,c) Polyaniline sensor, and (b,d) Nb₂CT_x/PAN sensor. Reprinted with permission from ref. [56]. Copyright 2021 Elsevier.

Figure 20

Technological and sustainable prospects of MXP-based ammonia sensor.