... Recently, chemiresistive gas sensors have attracted significant attention owing to their widespread and variety of applications including: (1) Indoor air quality monitoring (e.g., formaldehyde, benzene, carbon monoxide (CO), etc.) (Zhang et al., 2012;Saini et al., 2020;Marques et al., 2020); (2) Environmental air quality monitoring (e.g., greenhouse gas monitoring) (Honeycutt et al., 2019;Gupta et al., 2018;Bezzon et al., 2019;Manikandan et al., 2020); (3) Hazardous gas sensing (e.g., detecting explosion and toxic gases) (Lee et al., 2019;Duc et al., 2020;Kumar et al., 2020a); (4) Military applications (e.g., Chemical Warfare Agent) (Fennell et al., 2017;Jiang et al., 2018); (5) Food quality control and processing (e.g., prediction of meat freshness; detection of freshness of vegetables/fruits, and determining the time for freezing as well as the time of vegetables/fruits ripening) (Yousefi et al., 2019;Mustafa et al., 2020;Poyatos-Racionero et al., 2018); (6) Industrial production monitoring (e.g., methane sensing in mines; oil and gas positioning) (Honeycutt et al., 2019;Dai et al., 2020;Nikolic et al., 2020); (7) Agriculture industry (e.g., Ammonia (NH 3 ) acts as an anti-fungal agent and preservative in agriculture industry) (Kanaparthi et al., 2020;Ismail et al., 2020;Zhang et al., 2019b); (8) Automobile industry (e.g., sensing of polluted gases released from vehicles) Nazemi et al., 2019;Seekaew et al., 2019); (9) Animal and plant breeding (e.g., determining the time of cow oestrous) (Manzoli et al., 2019); (10) Medical care and disease diagnosis (e.g., detecting lung cancer, kidney malfunction, asthma, halitosis, and diabetes etc., can be evaluated through analyzing patients breath based on non-invasive nature and real time analysis) (Tang et al., 2020;Nasiri et al., 2019;Aroutiounian et al., 2020;Usman et al., 2019;Chen et al., 2019). Among these applications, indoor/outdoor air quality monitoring and environmental monitoring are highly demanded for maintaining standard air quality in the environment. ...