Dual-Selective and Humidity-Stable MoTe ₂ /Single-Walled Carbon Nanotube Sensors for ppt–ppb Level Detection of NO ₂ and Dimethylamine at Room Temperature

Dimethylamine (DMA) serves as a valuable biomarker for assessing seafood deterioration and quality, while nitrogen dioxide (NO2) represents a critical indoor and outdoor air pollutant. Although two-dimensional molybdenum ditelluride (MoTe2) has been identified as a viable NO2 sensor and single-walled carbon nanotubes (SWCNTs) are established for detecting nitrogen-based volatile amines such as DMA, a single material capable of discriminating between both analytes is lacking. To address this, we report a low-cost, dual-selective sensor based on a molybdenum ditelluride/single-walled carbon nanotube (MoTe2/SWCNT) composite for the simultaneous detection and discrimination of DMA and NO2. MoTe2 nanoparticles were synthesized via a simple one-pot hydrothermal method incorporating the COOH-functionalized SWCNTs. The effect of increasing SWCNT concentration (10 mg and 15 mg) on the composition and morphology was analyzed. The sensor with 10 mg of SWCNTs demonstrates dual detection, achieving limits of detection down to 50 ppm for DMA and 0.1 ppb for NO2 under ambient conditions across a high relative humidity range (50% to 90%). For 50 ppm DMA and 0.1 ppb NO2, the sensor exhibits clear relative responses of 0.8% and 11%, respectively, with recovery times in air of 2 min for DMA and 1.3 min for NO2. The theoretical limit of detection (LOD) for MoTe2-SW 10 is ≈1.7 ppm for DMA and 2 ppt for NO2. The composite MoTe2-SW 15 exhibited faster NO2 recovery time (1 min, 18 s quicker) but a lower relative response (≈1.8%) compared to SW 10 variant, with an LOD of approximately 18 ppt. The proposed composite provides an effective sensing platform for detecting these critical analytes. Its superior sensing properties─including rapid charge transfer, dual discrimination capability, and exceptional repeatability and reproducibility─arise from the formation of p–p heterojunctions and synergistic interactions between the MoTe2 and SWCNT components.