Polyvinyl alcohol wrapped multiwall carbon nanotube (MWCNTs) network on fabrics for wearable room temperature ethanol sensor

Wearable, room temperature operable, ethanol sensor was fabricated by spray layer by layer (sLbL) coating of (pyrolysis synthesized) multi-wall carbon nanotube (MWCNTs) followed by polyvinyl alcohol (PVA) on commercially available cotton fabrics. Transmission electron microscopy (TEM) analysis discovered that PVA present over MWCNTs. PVA/MWCNTs composites were characterized by Field Emission Scanning Electron Microscope (FESEM), Raman spectra and X-ray diffraction (XRD) analysis. Raman spectra show an increase in the intensity ratio of 'D' band to 'G' band (ID/IG) from 0.498 to 0.528 for MWCNTs and PVA/MWCNTs respectively that represent decoration of PVA on MWCNTs. PVA/MWCNTs coated cotton fabric sensor offer remarkable flexibility yielding stable sensor base resistance even after bending the sensor platform up to 60° on both forward and reverse directions. Gas sensing studies reveal that PVA wrapped MWCNTs fabric-based sensor show nearly 13-fold increase in the sensor response towards ethanol sensing compared to naked MWCNTs sensor. PVA/MWCNT fabric sensor showed higher selectivity towards ethanol sensing compared to ammonia, acetone, benzene, cyclohexane, methanol, toluene and xylene vapors with fast response (24 ± 2 s), recovery (29 ± 3 s) time and excellent reversibility at room temperature. The PVA coated MWCNTs sensor shows a good linear response (R2 = 0.983) under exposer of different concentration (100-500 ppm) of ethanol vapors. The calculated limit of detection (LOD) for PVA/MWCNTs towards ethanol was found 9.17 ppm. The possible gas sensing mechanism demonstrated based on a change in inter-tube contact resistance of PVA/MWCNTs due to ethanol vapor interaction and diffusion following by swelling of PVA layers. The results could be attractive to development of flexible, room temperature operable fabric based wearable gas sensing platforms.