Humidity Sensing Mechanism and Respiration Monitoring of WO₃ Nanoplates with a Monoclinic Crystal Phase

Abstract

Functioning of hydrothermally synthesized WO3 nanoplates was investigated for humidity sensing and respiration monitoring under different breathing conditions. The monoclinic phase was identified by X-ray diffraction. The average crystallite size was calculated by Williamson-Hall (W-H) plot (27 nm) and modified Scherrer equation (24 nm). The optical band gap was calculated as 2.7 eV using UV-Visible spectroscopy. The field emission electron microscopy and high resolution transmission electron microscopy micrographs of readied WO3 have confirmed the formation of microstructured nanoplates having an average diameter of 216 nm. Fluorine-doped tin oxide substrate was used for the deposition of film and also used as an electrode. The investigation of humidity was carried out at different relative humidity (RH)-11%, 33%, 44%, 54%, 74%, and 95%. The fabricated humidity sensor has shown excellent reversibility, stability and very small humidity hysteresis (<2%) at room temperature. The maximum response was observed as 41.95% at 95% RH with response and recovery time as 2 and 134 seconds, respectively. During the 30 days of observation, only a 0.4% decrease in response was observed. The fabricated WO3-based humidity sensor was investigated for human respiration having respiration rates of 2.51, 3.09, and 3.74 min-1.

Tailored mesoporous γ-WO3 nanoplates: unraveling their potential for highly sensitive NH3 detection and efficient photocatalysis

“…The LiCl (RH-11%), MgCl 2 (RH-33%), K 2 CO 3 (RH-44%), NaCl (RH-75%), and K 2 SO 4 (RH-95%) composed this saturated salt solution. 31 The formula shown below was used to determine the NH 3 concentration in parts per million (ppm): 32 where M , P , T , and R are the molecular weight of the target gas (g mol −1 ), pressure (Pa), temperature (K), and universal gas constant, respectively. The humidity of the surroundings was monitored using a computerized monitoring system.…”

“…The LiCl (RH-11%), MgCl 2 (RH-33%), K 2 CO 3 (RH-44%), NaCl (RH-75%), and K 2 SO 4 (RH-95%) composed this saturated salt solution. 31 The formula shown below was used to determine the NH 3 concentration in parts per million (ppm): 32 1 ppm…”