MXenes, a class of two-dimensional (2D) transition metal carbides and nitrides, have emerged as promising materials for high-performance gas sensors due to their unique combination of high electrical conductivity, tunable surface chemistry, and large specific surface area. This review highlights recent advances in MXene-based gas sensing materials, covering their synthesis strategies, structure–property relationships, and applications in both pristine and composite forms. We discuss conventional hydrofluoric acid etching and recent fluorine-free methods for MXene synthesis, and examine how these approaches affect surface terminations, interlayer spacing, and defect profiles relevant to gas sensing. The gas-sensing performance of pristine MXenes and their composites with metal oxides, transition metal dichalcogenides (TMDs), rGO, and conductive polymers is systematically analyzed, along with the underlying sensing mechanisms. Finally, current challenges and future perspectives for MXene-based gas sensors are addressed, with emphasis on enhancing sensitivity, selectivity, and ambient stability for next-generation sensing platforms.

Two-dimensional (2D) perovskites have gained much attention lately owing to their excellent optoelectronic properties, chemical tunability, and environmental stability. Multiple methods have been devised to synthesize high quality 2D perovskite single crystals, and recent progress in fabricating its heterostructures is notable as well. In particular, with growing interest in 2D van der Waals heterostructures, 2D perovskites have become a strong candidate as a new building block for heterostructures to reveal unique physical properties across different interfaces. Until now, various heterostructure devices of 2D perovskite single crystals with other types of 2D materials such as transition metal dichalcogenides (TMDs) and graphene have been studied, which have shown intriguing results including interlayer excitons and enhanced electronic properties. Here, we introduce various synthetic approaches to realize 2D perovskite single crystals and unique characteristics of their single crystal heterostructures fabricated with precision, possessing sharp interfaces. Moreover, recent studies of semiconductor devices based on 2D perovskite single crystal heterostructures are discussed in-depth. New perspectives to further the horizon in the field of 2D perovskite heterostructures are suggested in this work including the consideration of metal–2D material van der Waals contact, application of dry transfer techniques, electric bias driven ion diffusion studies, and nanocrystal array fabrication. 2D perovskite heterostructure single crystal devices factoring in these novel perspectives will further uncover the true potential of these materials for highly efficient and stable semiconductor devices.

The complex nature of ion migration at the nanoscale and the associated redox reaction in resistive switching requires a thorough understanding through transmission electron microscopy (TEM).

Porous pure SnO₂ nanofibers (NFs) and La₂O₃ nanoparticles (NPs)-embedded porous SnO₂ NFs were successfully synthesized via electrospinning followed by calcination. These materials were systematically evaluated as gas-sensing elements in metal-oxide-semiconductor (MOS) sensors. The La₂O₃ NPs embedded in porous SnO₂ NFs demonstrated superior gas-sensing performance compared to pure SnO₂ NFs. Specifically, the incorporation of La₂O₃ resulted in a 12-fold enhancement in gas-sensing response towards ethanol, significantly improving both sensitivity and selectivity by tuning the carrier concentration and modifying oxygen deficiencies and chemisorbed oxygen levels. Thus, La₂O₃ NPs embedded in SnO₂ NFs present a promising strategy for the development of high-performance ethanol gas sensors.