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Nanomaterial-based humidity sensors hold great promise for water vapor detection 13because of their high sensitivity and fast response/recovery. However, the condensation of water in 14nanomaterial films remains unclear from a physicochemical perspective. Herein, the condensation 15of water vapor in silica nanoparticle films was physicochemically analyzed to bridge the above gap. 16The morphology of surface-adsorbed water molecules was characterized using infrared absorption 17spectroscopy and soft X-ray absorption spectroscopy, and the effect of RH on the amount of 18adsorbed water was observed using a quartz crystal microbalance. The adsorbed water was found 19to exist in liquid- and ice-like states, which contributed to high and low impedance, respectively. 20The large change in film impedance above 80% RH was ascribed to the condensation of water 21between the nanoparticles. Moreover, RH alteration resulted in a colorimetric change in the film’s 22interference fringe. The obtained insights were used to construct an impedance-type portable 23humidity sensor with response and recovery times suitable for the real-time monitoring of water 24vapor in automated systems. Thus, this study clarifies the structure of water adsorbed on nanomaterial surfaces and, hence, the action mechanism of the corresponding humidity sensors, inspiring further research on the application of various nanomaterials to vapor sensing.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Sensor, Vapor, Condensation

Date published: 2023-11-14

Publisher: MDPI AG

Journal:

• Chemosensors (ISSN: 22279040) vol. 11 issue. 11 564

Funding:

• Japan Society for the Promotion of Science No. 18KK0141

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.3390/chemosensors11110564

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Updated at: 2024-09-03 08:30:22 +0900

Published on MDR: 2024-09-03 08:30:22 +0900