Fabrication of Nanofiber Metal Oxide-Based Gas Sensors For H2S and SO2 Gas Detection

Air pollution contains harmful gases such as carbon monoxide, dust/particles, sulfur dioxide (SO2), nitrogen oxides (NO3), and hydrogen sulfide (H2S). The TWA (time-weighted average) threshold of H2S gas is at 10 ppm and SO2 at 0.1–0.2 ppm and at the STEL (short-term exposure limit) threshold of H2S gas at 5–15 ppm and SO2 at 2–5 ppm (Asante, 2017). If the gas exceeds the threshold in the environment, it will cause various problems such as health, metals, buildings, animals and plants (Guo et al., 2015). Hydrogen Sulfide Gas (H2S) is one of the foul-smelling gases and is known as a toxic gas included in the gasotransmitter classification (Majhi et al., 2021). However, it is different from SO2 gas which has colorless characteristics that are odorless but highly reactive and easily soluble in water (B. Li & Ma, 2018). Therefore, a tool for H2S and SO2 gas detection is needed to prevent the impact caused by these gases (Mazumder et al., 2023).

The gas sensors that can be developed include flexible and wearable gas sensors, self-heated gas sensors, room temperature gas sensors, MEMS gas sensors (Chen et al., 2022). One type of gas sensor that has the advantage of detecting gas in a short time is the chermiresistive gas sensor (Lu et al., 2021). A chermiresistive sensor is a type of sensor that measures changes in electrical resistance in response to changes in concentration or chemical properties of a target substance (Kanth et al., 2023). The advantages of this gas sensor are high sensitivity, simple and economic, high portability, small size, long-term stability and does not require an external energy source. (Pippara et al., 2021). However, the current gas sensor has a weakness where the response time required is quite long and still uses high temperatures. Therefore, a material is needed for gas sensors that can detect gas in a short time using room temperature.

Nanofibers have gained attention in recent decades due to their high porosity, large surface area ratio, large specific to volume and small pore size with a diameter of 1–100 (Lim, 2017). Nanocomposite fiber is an alternative fiber development to optimize fiber in various applications (Sabetzadeh & Gharehaghaji, 2017). This composite material has the advantages of physical, mechanical, large surface area and many active surface sites so that it can accelerate the process of gas detection by chermiresistive gas (Cui et al., 2023). The electrospinning method is one of the good methods of making nanofibers because the advantages of low cost, energy saving, and a large surface (Nadaf et al., 2022).

Polymer and metal oxide-based nanofiber composites have the advantage of producing fibers with good mechanical properties and chemical properties. Polyanylene polymer is one of the candidates for conductive organic polymers that can conduct electricity (Talegaonkar & Patil, 2016). However, the level of conductivity is still relatively low so it needs a composite material or dopant to increase its conductivity. SnO2 material is one of the n-type semiconductor materials with a band gap of 3.6 eV which means it has more free electrons moving than holes so that it can be composited with polymers in gas sensor applications (J Sharma et al., 2017). The p-type material candidates such as cooper oxide (CuO) with a band gap of 1.2 eV- 1.4 eV which means there are more free-moving holes than free-moving electrons so it is quite interesting to composite with polymers to improve conductivity in gas sensors (Ashokan et al., 2015).

Previous research conducted by Sharma, et.al in 2017, PANI composite SnO2 can detect H2 gas at room temperature and can respond in less than 30 seconds (J Sharma et al., 2017). Another study was conducted by Esmaeeli, et.al in 2017 using PANI composite CuO on FTO substrate without any data related to response time and temperature used (Esmaeeli et al., 2018). Therefore, this study focuses on the development of polymer-based ceramic nanofiber with semiconductor and metal oxide by electrospinning method to detect resistance changes in gas using chermiresistive gas sensor at room temperature and short time. This research modifies the nanofiber with various concentrations of precursors to determine the effectiveness of response time and temperature by chermiresistive gas sensor.

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