Ultrafast Detection and Discrimination of Methanol Gas Using a Polyindole-Embedded Substrate Integrated Waveguide Microwave Sensor

Abstract

The fast and sensitive detection of methanol gas using cost-effective sensors in the industry is a significant issue to be addressed. Herein, a polyindole (PIn)-deposited substrate integrated waveguide (SIW) has been introduced to perform quantitative and qualitative methanol gas sensing with quick response and recovery time at room temperature. First, PIn is synthesized and deposited in the microwell etched at the intensified electric field region of the microwave-based cavity resonator, which gives a sensing response through variation of PIn's high-frequency conductivity and dielectric property caused by the adsorption and desorption of methanol gas. Second, an enhanced filling factor and high Q factor have been attained using the proposed microwell etched SIW structure, which exhibits high sensitivity in terms of frequency shift (3.33 kHz/ppm), amplitude shift (0.005 dB/ppm), bandwidth broadening (3.66 kHz/ppm), and loaded Q factor (10.60 Q value/ppm). Third, the gas measurement results reveal excellent long-term stability with a relative standard deviation (RSD) of 0.02% for 7 days, excellent repeatability with an RSD of 0.004%, and desired response and recovery time of 95 and 120 s, respectively. The results indicate that the proposed microwave sensor has great potential to achieve high sensitivity and fast response toward methanol gas molecules at room temperature.

Polyindole and polypyrrole as a sustainable platform for environmental remediation and sensor applications

“…Polyindole (PIN), a rising conducting polymer, is being explored and developed as a possible candidate for electrochromic devices 33,34 , sensors 35,36 , photocatalysis 37,38 , and electrocatalysis 39 , anticorrosion 40,41 , diodes 42,43 , supercapacitors 44,45 , batteries, and biology-related applications [45][46][47] . The studies on PIN has been started as early as 1976, Youmans, H. L et.al synthesised polyindole from indole through chemical polymerization 48 .…”

“…Methanol gas is one of the hazardous VOC gases produced from industrial processes, agricultural waste, and fossil fuels, which can cause disturbances in the metabolism of the human body 35 . Excellent work is reported by Alok Kumar et al, where a substrate integrated waveguide (SIW) sensor was developed by depositing polyindole (PIN) can be used for methanol sensing quantitatively and qualitatively at room temperature 35 .…”

“…Methanol gas is one of the hazardous VOC gases produced from industrial processes, agricultural waste, and fossil fuels, which can cause disturbances in the metabolism of the human body 35 . Excellent work is reported by Alok Kumar et al, where a substrate integrated waveguide (SIW) sensor was developed by depositing polyindole (PIN) can be used for methanol sensing quantitatively and qualitatively at room temperature 35 . The deposited polyindole was placed at the intensified electric field region of the microwave-based cavity resonator and the changes in high-frequency conductivity and dielectric property activated by the adsorption and desorption of methanol gas enables fast methanol sensing.…”

PVP derived nitrogen-doped porous carbon integrated with polyindole: nano/microspheres assembled by emulsion polymerization for asymmetric supercapacitors

“…28 Thus, PIn exhibits air-stable conductivity, good thermal stability, and environmental stability properties, which makes it as a promising candidate for applications in various fields, such as anti-corrosion coating, 29 catalysis/electrocatalysis, 30,31 electrochromic devices 32 and sensors. 33,34 In addition, when employed in aqueous-based supercapacitors, PIn possesses a competitive redox potential and slower rate of hydrolytic degradation compared to polypyrrole and polyaniline. However, the fragile backbone of PIn results in inferior cycling stability, which puts it at a disadvantage compared with its counterparts.…”

Simultaneous microwave-assisted reduction and B/N co-doping of graphene oxide for selective recognition of VOCs

“…These include metals and metal oxides, solid electrolytes, polymers, and ionic salts. [14][15][16] However, high operating temperatures (4100 1C), extreme sensitivity to humidity, and poor selectivity to ethanol for most of the commonly used active materials hinder their fundamental application as high-performance methanol sensing devices. On the other This journal is © The Royal Society of Chemistry 2022 hand, the use of layered two-dimensional (2D) materials, specifically graphene-based materials, offers a new avenue for improving the sensitivity and selectivity for room temperature methanol and/or ethanol detection due to their high thermal conductivity, mechanical strength and chemical stability.…”