Carbon nanotubes (CNTs) have become one of the most widely investigated nanomaterials for gas sensing because their nearly one-dimensional geometry, large surface-to-volume ratio, hollow structure, and tunable metallic or semiconducting character allow trace adsorption events to be transduced into measurable electrical signals at or near room temperature. This review summarizes CNT-based gas sensors from a system-oriented perspective, linking four interconnected topics: (i) CNT structure, synthesis, and film/device fabrication; (ii) sensing mechanisms, including charge transfer, Schottky-barrier modulation, carrier-lifetime effects, and field-enhanced ionization; (iii) functional interfaces based on noble metals, metal oxides, conducting polymers, and graphene derivatives; and (iv) gas-specific and flexible/wearable device performance. Particular attention is given to recent room-temperature and mechanically compliant CNT-film sensors fabricated on polymer, cellulose, paper, textile, and mask substrates. Rather than cataloguing only individual response values, this review compares representative devices in terms of target gas, operating condition, sensitivity, recovery strategy, selectivity, humidity tolerance, and wearable relevance. The review concludes by discussing remaining challenges in reproducibility, selectivity, humidity compensation, recovery, power consumption, and standardization, and by outlining future directions toward robust, scalable, and intelligent CNT-enabled sensing systems.

In this study, a high-performance MoS₂-based strain-gauge pressure was sensor fabricated entirely below 80 °C, enabling direct integration onto flexible polyethylene terephthalate (PET) substrates. The sensor comprised a three-layer MoS₂ channel (~2 nm) patterned via dry transfer and O₂/Ar plasma etching, interfaced with Cr/Au electrodes. This wafer-scale and cost-effective fabrication route preserves the crystallinity of the film and prevents substrate degradation. The sensor achieved a gauge factor of ~104 under compression, representing a fifty-fold improvement over conventional metal foil gauges (~2), with a linear response across both compressive and tensile regimes. Mechanical robustness was confirmed through repeated bending and tape adhesion tests, with no degradation in electrical performance. When configured as a Wheatstone bridge, this device exhibits normalized sensitivity suitable for real-time monitoring, with response and recovery times below 200 ms. These results establish O₂/Ar-plasma-patterned MoS₂ architectures as a scalable, cost-effective platform for next-generation flexible sensors, outperforming metal-foil technology in applications including seat-occupancy detection, wearable physiological monitoring, and tactile interfaces for soft robotics.

The use of LIDAR sensors is rapidly increasing across various fields, including autonomous transportation, robotics, security systems, and biosensing. Among the core components of LIDAR systems, short-wave infrared (SWIR) sensors play a crucial role in detecting infrared light reflected from objects to recognize the surrounding environment and humans. Various types of SWIR sensors have been reported, with growing demand for those capable of detecting eye-safe infrared wavelengths above 1400 nm. In particular, quantum dot (QD)-based SWIR sensors are attracting attention due to their tunable wavelength range within the eye-safe region, narrow full width at half maximum (FWHM), and selective detection with minimal interference from other infrared wavelengths. Moreover, QD-based SWIR photodetectors can be synthesized and fabricated via solution-based methods, offering advantages such as low cost and ease of fabrication. However, the long organic ligands typically present on QDs exhibit insulating properties, limiting the sensitivity and stability of the photodetectors. To address this issue, organic ligands can be replaced with short inorganic ligands possessing superior electrical conductivity. In this study, the organic ligands of synthesized PbS QDs were replaced with the inorganic ligand methylammonium lead iodide (MAPI) in solution, and a SWIR photodetector was fabricated. The MAPI-capped PbS QD-based photodetector exhibited remarkable external quantum efficiency (EQE) of 62%, a responsivity of 0.73 A/W, and a detectivity of 2.26 × 10¹¹ Jones within the 1400–1500 nm wavelength range.

This work presents the design and evaluation of cerium and zinc oxide-incorporated indium oxide (Ce/ZnO-In₂O₃) nanocube composites synthesized via a hydrothermal process for advanced ethanol gas sensing. The incorporation of Ce and ZnO effectively modified the surface chemistry and electronic structure of In₂O₃ without causing significant morphological degradation. Compared with pristine In₂O₃, the Ce/ZnO-In₂O₃ sensor exhibited a significantly enhanced response of 33.2 toward 100 ppm ethanol at 300 °C, corresponding to an 8.7-fold improvement, along with a low detection limit of 0.8 ppm. In addition, the composite sensor demonstrated stable and reversible sensing behavior, excellent repeatability over 100 cycles, and long-term operational stability. Notably, improved humidity tolerance was achieved, with approximately 77% of the initial response retained at 80% relative humidity. The enhanced sensing performance is attributed to the combined effects of heterojunction formation between ZnO and In₂O₃ and Ce-induced lattice distortion, which promote oxygen adsorption and facilitate charge transfer during gas reactions. Principal component analysis (PCA) further confirmed the improved discrimination of ethanol against interfering gases. These results underscore the synergistic effects of Ce and ZnO incorporation in tailoring electronic structures and surface chemistry, thereby emphasizing the potential of this strategy for reliable ethanol detection in environmental and industrial applications.