The sol–gel template synthesis of porous TiO₂for a high performance humidity sensor

Abstract

This research develops a simple template assisted sol-gel process for preparing porous TiO2 for a high performance humidity sensor. Tetraethyl orthosilicate (TEOS) as a template was directly introduced into TiO2 sol formed by the hydrolysis and condensation of titanium alkoxide; the following calcination led to the formation of TiO2-SiO2 composite, and the selective removal of SiO2 by dilute HF solution led to the formation of porous structure in TiO2. The resulting porous TiO2-based sensor exhibits high sensitivity and linear response in the wide relative humidity (RH) range of 11%-95%, with an impedance variation of four orders of magnitude to humidity change. Moreover, it exhibits a rapid and highly reversible response characterized by a very small hysteresis of <1% RH and a short response-recovery time (5 s for adsorption and 8 s for desorption), and a 30-day stability test also confirms its long-term stability. Compared with pure TiO2 prepared by the conventional sol-gel method, our product shows remarkably improved performance and good prospect for a high performance humidity sensor. The complex impedance spectra were used to elucidate its humidity sensing mechanism in detail.

High sensitivity and fast response graphene oxide capacitive humidity sensor with computer-aided design

“…Here we present a computer-aided design to predict the transient response and steady response of these capacitive sensors. We find that humidity sensors based on GO can overcome the existing problems reported in literature [23][24][25][26][27][28][29][30], and exhibit ultrahigh humidity sensitivity, as well as short response time. properties of the presented sensor are investigated over a wide range of 0-100% relative humidity at room temperature.…”

“…As described in the papers [14,25], the increase of RH makes c increase. Such that the capacitance increases.…”

“…It is obvious that the capacitance value increases with increasing of RH levels monotonically. The relationship can be expressed by following equation (1) [25].…”

Humidity sensor based on Ga2O3 nanorods doped with Na+ and K+ from GaN powder

“…indicate that protonic transport and electrolytic conduction dominate the conduction mechanisms at low and high RH, respectively [45] .…”

Humidity sensor based on electrospun (Na0.5Bi0.5)0.94TiO3–Ba0.06TiO3 nanofibers

“…So the capacitance of NBT-BT6 nanofiber humidity sensor is independent of frequency. With increasing the RH (75%, 85%, and 95%), more and more water molecules are adsorbed, and the leak conduction is appeared [38]. The capacitance C can be represented by using the following expression [39]:…”