Quartz Crystal Microbalance Humidity Sensors Based on Structured Graphene Oxide Membranes with Magnesium Ions: Design, Mechanism and Performance.

Ruobing Yi,Liang Chen,Lei Zhang,Yimin Zhao,Dexi Nie,Bingquan Peng

doi:10.3390/membranes12020125

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

Introduction

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]

Methods

Results

Conclusion