Vapor deposition of ultrathin hydrophilic polymer coatings enabling candle soot composite for highly sensitive humidity sensors. (June 2022)

• Record Type: Journal Article
• Authors: Su, P.; Liu, W.; Hong, Y.; Ye, Y.; Huang, S.
• Is Part Of: Materials today chemistry. Volume 24(2022)
• Publication Date: 2022-06
• Subjects: Candle soot -- Hydrophilic polymer -- Initiated chemical vapor deposition -- Humidity sensor -- Respiratory monitoring; Chemistry -- Periodicals; Materials -- Research -- Periodicals; Materials science -- Periodicals; Chemistry; Materials -- Research; Electronic journals; Periodicals; 660.282
• DOI: 10.1016/j.mtchem.2022.100786
• Languages: English
• ISSNs: 2468-5194

Abstract

Abstract: Candle soot (CS) is a desirable carbon nanomaterial for sensors owing to its highly porous nanostructure and large specific surface area. CS is advantageous in its low-cost and facile preparation compared to graphene and carbon nanotubes, but its pristine nanostructure is susceptible to collapse, hampering its application in electronic devices. This article reports conformal coating of nanoscale crosslinked hydrophilic polymer on CS film using initiated chemical vapor deposition, which well preserved the CS nanostructure and obtained nanoporous CS@polymer composites. Tuning coating thickness enabled composites with different morphologies and specific surface areas. Surprisingly, the humidity sensor made from composite with the lowest filling degree, thus largest specific surface area, showed relatively low sensitivity, which is likely due to its discontinuous structure, thus insufficient conductive channels. Composite sensor with optimum filling degree shows excellent sensing response of more than 10 3 with the linearity of R 2 = 0.9400 within a broad relative humidity range from 11% to 96%. The composite sensor also exhibits outstanding sensing performance compared to literature with low hysteresis (3.00%), a satisfactory response time (28.69 s), and a fast recovery time (0.19 s). The composite sensor is fairly stable and durable even after 24 h soaking in water. Furthermore, embedding a humidity sensor into a face mask realizes real-time monitoring of human breath and cough, suggesting promising applications in respiratory monitoring. Graphical abstract: Image 1 Highlights: Initiated chemical vapor deposition of hydrophilic polymer enables nanoporous candle-soot-based composite. Coating thickness affects composite morphology and sensing performance. Composite sensor with optimum filling degree exhibits excellent sensing performance. Such performance owes to large surface area and abundant conductive channels. The composite sensor is able to monitor various human respiratory behavior.