Abstract
The application of graphene oxide (GO)-based membranes combined with a quartz crystal microbalance (QCM) as a humidity sensor has attracted great interest over the past few years. Understanding the influence of the structure of the GO membrane (GOM) on the adsorption/desorption of water molecules and the transport mechanism of water molecules in the membrane is crucial for development of applications using GOM-based humidity sensors. In this paper, by investigating the effects of oxygen-containing groups, flake size and interlayer spacing on the performance of humidity sensing, it was found that humidity-sensing performance could be improved by rational membrane-structure design and the introduction of magnesium ions, which can expand the interlayer spacing. Therefore, a novel HGO&GO&Mg2+ structure prepared by uniformly doping magnesium ions into GO&HGO thin composite membranes was designed for humidity sensing from 11.3% RH to 97.3% RH. The corresponding sensor exhibits a greatly improved humidity sensitivity (~34.3 Hz/%RH) compared with the original pure GO-based QCM sensor (~4.0 Hz/%RH). In addition, the sensor exhibits rapid response/recovery times (7 s/6 s), low hysteresis (~3.2%), excellent repeatability and good stability. This research is conducive to understanding the mechanism of GOM-based humidity sensors. Owing to its good humidity-sensing properties, the HGO&GO&Mg2+ membrane-based QCM humidity sensor is a good candidate for humidity sensing.
Highlights
There is an increasing demand for high-precision and sensitive real-time humidity detection, which is important for traditional industries, such as agriculture [1], grain storage [2] and industrial production, and for high-tech industries, such as semiconductor technology, huma-health real-time detection and clean energy storage [3,4]
Our results show that the introduction of magnesium ions remarkably improved the sensor performance of graphene oxide (GO)- and HGO-based humidity sensors
It can be clearly seen that the framework is composed of GO and HGO flakes with different lateral sizes
Summary
There is an increasing demand for high-precision and sensitive real-time humidity detection, which is important for traditional industries, such as agriculture [1], grain storage [2] and industrial production, and for high-tech industries, such as semiconductor technology, huma-health real-time detection and clean energy storage [3,4]. QCMs have the ability to monitor mass changes at the sub-nanogram level [5,6,7], as well as convert the dynamic-adsorption mass change of thin membranes deposited on electrodes into resonance-frequency-shift information [8,9] These virtues are required in humidity sensors. The materials coating a QCM are the key to determining the detection performance of QCM-based humidity sensors [10,11]. Various materials, such as two-dimensional (2D) materials [11,12], polyelectrolytes [13] and metal oxides [14], have been researched. There have been many efforts in recent years to improve the humidity-sensing performance of GO-based sensors by cross-linking GO with hydrophilic materials, such as polymers [23], metal oxides [14] and nanodiamonds [24]
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