Physisorption-Mediated Charge Transfer in TiS2 Nanodiscs: A Room Temperature Sensor for Highly Sensitive and Reversible Carbon Dioxide Detection

Real-time and high-performance monitoring of trace carbon dioxide (CO₂) has become a necessity due to its substantial impact on the global climate, human health, indoor occupancy, and crop productivity. Two-dimensional materials such as transition metal dichalcogenides (TMDs) have gained significant interest in gas sensing applications owing to their intrinsically high surface-to-volume ratio. However, the research has been limited to prominent TMDs such as WS₂ and MoS₂. Specifically, the chemiresistive sensing performance of titanium disulfide (TiS₂) has rarely been investigated. We present an electric-field-assisted TiS₂ nanodisc assembly for the fabrication of a low-cost, low-power CO₂ gas sensor based on charge transfer between physisorbed CO₂ analyte molecules and TiS₂ nanodiscs operating at room temperature. The physiochemical properties of the synthesized TiS₂ nanodiscs were investigated via scanning electron microscopy (SEM), electron diffraction spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. The fabricated sensor demonstrated an ultra-high sensor response of 60%, a fast response time of 37 s toward 500 ppm CO₂ gas, and the lowest detection limit of 5 ppm under ambient conditions. The low adsorption energies and vdW interaction between CO₂ molecules and TiS₂ resulted in easy desorption, allowing the sensor to self-recover without the need for external stimuli, which is hardly been witnessed in other 2D material analogues. Furthermore, the sensor has excellent reproducibility and stability for successive analyte exposures, as well as excellent selectivity for CO₂ over other interfering gases. This reported sensor based on 2D TMDs is the first of its type to integrate such a broad range of sensor characteristics (such as high sensor response and sensitivity, rapid response and recovery times, a high signal-to-noise ratio, and excellent selectivity at room temperature) into a single, revolutionary device for CO₂ detection.