MoS₂/MoO_<i>x</i> Nanoflake-Based Dual-Functional Antenna Sensors for Highly Sensitive and Selective Detection of Volatile Organic Compounds

In this paper, we present for the first time a highly sensitive, dual-functional antenna sensor functionalized with molybdenum disulfide/oxide heterostructures (MoS2/MoOx NFs) for selective detection of methanol gas and wireless communications, simultaneously. The proposed antenna sensor uniquely features optimized deposition of the sensing material and structure, allowing sensitive, selective gas detection without interrupting communication. The sensing materials were synthesized via a simple hydrothermal method and characterized using scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). XRD and XPS analysis confirmed the formation of MoS2/MoOx heterostructure and indicated the presence of oxide states within the structure. First, the gas sensing ability and electrical properties of MoS2 NF were investigated using chemiresistive transducers. Integrating this with a wideband monopole antenna, a highly sensitive, dual-functional antenna sensor was developed. We optimized the sensing material for sensitivity and tested against volatile organic compounds. Chemiresistive sensors exhibit linear detection but suffer initial fluctuations and baseline shifts at room temperature, which can be mitigated using antenna sensors with RF signals. The sensor demonstrated high selectivity, with methanol producing the strongest response among equal concentrations of methanol, ethanol, isopropanol, and acetone. The developed antenna sensor exhibited high sensitivity of approximately 1 MHz/1000 ppm against methanol. In addition, the calculated detection limit (DL) of the antenna sensor was 52 ppm, which is significantly lower than that of the chemiresistive sensor (799 ppm). The results indicated that with a lower DL than the safety threshold for methanol (200 ppm), the proposed antenna sensor is ideal for monitoring methanol gas in risky indoor environments. Moreover, the sensor’s gas sensing capability does not affect the antenna’s communication performance, indicating its potential for seamless integration into wireless sensor networks.