Humidity-sensing Performance Research Articles

A gold nano-urchin-decorated quasi-freestanding graphene-based humidity sensor with enhanced responsivity and a wide relative humidity detection range for real-time applications

Excellent humidity response and detection threshold are essential attributes of a humidity sensor. In this study, quasi-freestanding graphene (QFSG) was grown epitaxially on vicinal silicon carbide via thermal annealing, followed by decoration with hydrophilic gold nano-urchins (AuNUs). The resulting humidity sensor consistently achieved highly effective non-contact humidity-sensing performance, which can be used to monitor breathing and skin moisture. The proposed humidity sensor demonstrated a non-linear response of ∼119.98 % over a wide relative humidity detection range of 4–96 % at a frequency of 1 kHz, outperforming a QFSG-only humidity-sensing device (∼11.92 % and 22–84 % relative humidity, respectively). This 10-fold increase in humidity response and wider detection range is attributed to the hydrophilicity and plasmonic behavior of the AuNUs. It also demonstrated transient impedance response/recovery time of 4.5 and 3.0 s, respectively; low hysteresis of 3.6 %; and stability over 25 days, which are key factors for effective humidity sensing. The fast response and sensitivity of the AuNUs/QFSG humidity sensor made it possible to test for various real-time monitoring applications such as human breathing and non-contact proximity testing.

Copper abietate/polyvinyl acetate composite film for enhanced humidity sensing in Chinese herbal medicine monitoring systems

Sensing materials derived from natural and biodegradable sources are increasingly being developed and applied to realize environmentally friendly technologies. In this paper, we present the synthesis, characterization, and application of a novel copper abietate/polyvinyl acetate (CuA/PVAc) composite film, specifically engineered to enhance the humidity-sensing capabilities of Chinese herbal medicine monitoring systems. The sensing material was synthesized by strategically melding copper abietate, a natural renewable material, with PVAc to exploit their combined synergistic properties for optimal humidity-sensing performance. Comprehensive characterization techniques, including inductively coupled plasma optical emission spectrometry (ICP-OES), field-emission scanning electron microscopy (FESEM), water contact angle measurements, and Fourier transform infrared (FT-IR) spectroscopy, were employed to confirm the formation of CuA/PVAc composites. These analyses confirmed the homogeneity and intended chemical composition of the composite films.The resultant CuA-1/PVAc-4 (0.4 μg/μL) composite film exhibited a good logarithmic relation (0.9988) with relative humidity (RH) over a wide range (11 %–97 %) and high sensitivity (24.55 Hz/%RH). Moreover, this study introduces a novel, eco-friendly approach by integrating the CuA/PVAc composite with a quartz crystal microbalance (QCM) sensor and a sophisticated wireless circuit that enables real-time, Wi-Fi-based humidity monitoring tailored for the preservation of Chinese herbal medicines. The implementation of this wireless humidity detection system represents a significant advancement in the application of environmentally friendly materials in sensor technology and offers a practical and scalable approach for precise environmental monitoring.

To study the enhanced humidity-sensing performance of rGO/ZnO heterostructure compared to pure ZnO and its practical utility in contactless sensing device

To study the enhanced humidity-sensing performance of rGO/ZnO heterostructure compared to pure ZnO and its practical utility in contactless sensing device

Designing High Performance Carbon/ZnSn(OH)6-Based Humidity Sensors.

In this work, pure phase and carbon/ZnSn(OH)6 samples were synthesized by a hydrothermal method. The composite sample's structure, morphology, and functional groups were investigated by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. Subsequently, ZnSn(OH)6 samples were modified with different carbon contents, and their humidity-sensing properties were investigated. The introduction of carbon increased the specific surface area of pure ZnSn(OH)6 samples, thus significantly improving the sensors' humidity sensing response. The C10-ZnSn(OH)6 sensor exhibited a high response, up to three orders of magnitude, a humidity hysteresisof 13.5%, a fast response time of 3.2 s, and a recovery time of 24.4 s. The humidity sensor's possible humidity sensing mechanism was also analyzed using the AC complex impedance puissance method with a simulated equivalent circuit. These results revealed that ZnSn(OH)6 can effectively detect ambient humidity and that the introduction of carbon significantly improves its humidity-sensing performance. The study provides an effective strategy for understanding and designing ZnSn(OH)6-based humidity sensors.

Polydopamine-modified MXene/cellulose nanofibers composite film for self-powered humidity sensing and humidity actuating

Humidity sensors are of great significance in the domains of wearable electronic products, environmental and food quality monitoring, and human healthcare. In general, they necessitate an external power source in the form of a battery. Despite considerable efforts, developing self-powered sensing systems without reliance on an external power supply remains a major challenge. Herein, an electrochemical humidity sensor with primary battery structure based on redox reaction was designed, in which polydopamine (PDA)-modified MXene/TEMPO-oxidized cellulose nanofibers/LiCl (PDMM/TOCNFs/LiCl) composite film serves as electrolyte layer. The introduction of TOCNFs confers outstanding structural stability and superior tensile strength upon the composite film. Importantly, the hygroscopic and ionic conductivity properties of the PDMM/TOCNFs/LiCl electrolyte allow the sensor to generate spontaneous voltage over a wide relative humidity (RH) range of 11 – 91%. In addition, the developed sensor exhibits excellent humidity-sensing performances, including high voltage response, fast response/recovery time, and superior humidity-sensing stability. Moreover, mussel-inspired PDA improves the ambient stability of MXene by engineering interfacial interactions, which imparts the hygroscopic PDMM/TOCNFs/LiCl composite film with desirable stability for practical applications. Finally, the potential applications of the sensor and the composite film in human respiration, non-contact sensing, and humidity actuating are demonstrated. This work paves the way for the development of an innovative self-powered humidity sensing system.

Fully Printed Cellulose Nanofiber-Ag Nanoparticle Composite for High-Performance Humidity Sensor.

This paper reports a high-performance humidity sensor made using a novel cellulose nanofiber (CNF)-silver nanoparticle (AgNP) sensing material. The interdigital electrode pattern was printed via reverse-offset printing using Ag nano-ink, and the sensing layer on the printed interdigitated electrode (IDE) was formed by depositing the CNF-AgNP composite via inkjet printing. The structure and morphology of the CNF-AgNP layer are characterized using ultraviolet-visible spectroscopy, an X-ray diffractometer, field emission scanning electron microscopy, energy-dispersive X-ray analysis, and transmission electron microscopy. The humidity-sensing performance of the prepared sensors is evaluated by measuring the impedance changes under the relative humidity variation between 10 and 90% relative humidity. The CNF-AgNP sensor exhibited very sensitive and fast humidity-sensing responses compared to the CNF sensor. The electrode distance effect and the response and recovery times are investigated. The enhanced humidity-sensing performance is reflected in the increased conductivity of the Ag nanoparticles and the adsorption of free water molecules associated with the porous characteristics of the CNF layer. The CNF-AgNP composite enables the development of highly sensitive, fast-responding, reproducible, flexible, and inexpensive humidity sensors.

Efficient Electron Transfer through Interfacial Water Molecules across Two-Dimensional MoO3 for Humidity Sensing.

Resistive humidity sensors are required in flexible and integrated devices. Two-dimensional MoO3 offers a large interface area, enabling the modulation of its electrical properties over a wide range. In this study, 2D MoO3 was synthesized via liquid-phase exfoliation for humidity-sensing tests. In terms of high sensitivity, negligible hysteresis, linearity, and stability, the humidity-sensing performance of MoO3 is superior to those of other materials. The sensitivity reaches 9794 Ω/RH at 25 °C. The sensing mechanism of MoO3 was investigated by using impedance spectra and voltage-current scans under different humidity levels. The results indicate that the resistance change of MoO3 due to humidity originates from the interfacial conductance. Interfacial H2O adsorption induces efficient conducting paths via hydrogen bonding, decreases the potential barrier for electron transfer, and supplies additional electron states to the valence bands. In this study, electronic humidity sensing was investigated in depth, and a new perspective was proposed for electronic humidity sensing.

Low-cost ZnO incorporated carbonized nitrile butadiene rubber (NBR) as a relative humidity monitoring sensor

This paper presents the development and characterization of a sustainable humidity sensor that is both cost-effective and high performing. The sensor utilizes a composite material comprising conductive carbon derived from recycled Nitrile Butadiene Rubber (NBR) gloves and zinc oxide (ZnO). Among the various chemical compositions tested, the sensor with a carbon-to-zinc oxide (C:ZnO) ratio of 1:0 exhibited superior humidity-sensing performance. The study encompassed a broad spectrum of relative humidity levels, ranging from 5% to 95% at room temperature (25 °C) at an optimum frequency of 100 Hz. The sensor exhibited remarkable characteristics, including a minimal hysteresis of only 0.36%, indicating its ability to provide consistent and accurate readings. Moreover, the sensor demonstrated excellent long-term stability, ensuring reliable performance over extended periods. Additionally, the sensor showcased rapid and dependable sensing capabilities, with a response time of 18 s and a recovery time of 16 s. This indicates its ability to detect and recover from changes in humidity levels promptly. The composite material's high sensitivity to relative humidity variations can be attributed to the presence of zinc oxide nanoparticles (NPs), which have an affinity for water molecules and facilitate interaction. To assess its performance, the developed sensor was compared to most previous work in the literature and the results revealed that the proposed sensor exhibits comparable levels of accuracy and reliability. This work provides a simple, cost-effective strategy for fabricating high-performance humidity sensors by exploring waste materials like NBR.

ZIF-90-Derived Porous ZnO Coated Optical Microfiber Interferometer Sensor for Enhanced Humidity Sensing and Breath Monitoring.

Humidity plays an important role in many fields, and the realization of high sensitivity and fast response simultaneously for humidity detection is a great challenge in practical application. In this work, we demonstrated a high-performance relative humidity (RH) sensor made by supporting zeolitic imidazolate framework-90 (ZIF-90)-derived porous zinc oxide (ZnO) onto an optical microfiber Sagnac interferometer (OMSI). The ZIF-90-modified OMSI (ZIF-90-OMSI) sensor was in situ heated at different temperatures to obtain porous ZnO, and their humidity-sensing properties were investigated ranging from 25 to 80% RH. The experimental results showed that the porous ZnO fiber sensor prepared at 500 °C (Z500-OMSI) exhibited best humidity-sensing performance with a high sensitivity of 96.2 pm/% RH (25-45% RH) and 521 pm/% RH (50-80% RH) and ultrafast response/recovery time (62.37/206.67 ms) at 22.3% RH. These performances were attributed to the complete transformation of ZIF-90 to ZnO at 500 °C. The obtained Z500 not only retained the high porosity and specific surface area of ZIF-90 but also exhibited the exceptional hydrophilicity of ZnO. In addition, the signals of the proposed Z500-OMSI sensor changed with different breathing patterns, indicating the possibility for human respiration monitoring. This work provided a reliable candidate for an effective RH monitoring system with potential application in medical diagnoses, industrial production, environmental detection, and human health monitoring.

Ultrasensitive Humidity Sensors with Synergy between Superhydrophilic Porous Carbon Electrodes and Phosphorus-Doped Dielectric Electrolyte.

Capacitive humidity sensors have been used for human health monitoring, but their performance may be poor in terms of sensitivity and response time, because of limitations in sensing materials and insufficient knowledge about sensing mechanisms. Herein, a new combination of humidity sensing materials to assemble thin-film based capacitive-type sensors is proposed by using PA-doped polybenzimidazole (PA-PBI) as an electrolyte and laser-carbonized PA-PBI as a carbon electrode (PA-PBI-C). Based on PA involved laser scribing, the flexible sensor can reach excellent humidity-sensing performances with an ultrahigh sensitivity (1.16 × 106 pF RH%-1, where RH represents the relative humidity), a superior linearity (R2 = 0.9982), a fast response time (0.72 s), and a low hysteresis in a wide RH range from 1% to 95%. By further studying P-O decorated porous carbon electrode with superhydrophilicity and the solid-state dielectric electrolyte featured by a high dielectric constant, a synergistic sensing mechanism consisting of a "Water reservoir" and a "Bridge" is established to support advanced health-monitoring applications such as the respiration patterns and skin condition where both sensitivity and response time are critical.

Optimization of Aluminum Dopant Amalgamation Immersion Time on Structural, Electrical, and Humidity-Sensing Attributes of Pristine ZnO for Flexible Humidity Sensor Application

This study synthesized pristine and aluminum (Al)-doped zinc oxide (Al:ZnO) nanostructures through a simplistic low-temperature ultrasonicated solution immersion method. Al:ZnO nanostructures were synthesized as a sensing material using different immersion times varying from two to five hours. The Al:ZnO nanostructured-based flexible humidity sensor was fabricated by employing cellulose filter paper as a substrate and transparent paper glue as a binder through a simplistic brush printing technique. XRD, FESEM, HRTEM, EDS, XPS, a two-probe I–V measurement system, and a humidity measurement system were employed to investigate the structural, morphological, chemical, electrical, and humidity-sensing properties of the pristine ZnO and Al:ZnO nanostructures. The structural and morphological analysis confirmed that Al cations successfully occupied the Zn lattice or integrated into interstitial sites of the ZnO lattice matrix. Humidity-sensing performance analysis indicated that the resistance of the Al:ZnO nanostructure samples decreased almost linearly as the humidity level increased, leading to better sensitivity and sensing response. The Al:ZnO-4 h nanostructured-based flexible humidity sensor had a maximum sensing response and demonstrated the highest sensitivity towards humidity changes, which was noticeably superior to the other tested samples. Finally, this study explained the Al:ZnO nanostructures-based flexible humidity sensor sensing mechanism in terms of chemical adsorption, physical adsorption, and capillary condensation mechanisms.

Significantly Improved Humidity Performance of La2O3-Based Sensor Modified by Li, Na, and K+ Ions

The effects of Li+, Na+, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{K}^{+}$ </tex-math></inline-formula> ions loading on the humidity-sensing performances of La2O3-based humidity sensors were investigated in detail. Single-ion loading shows that Li+-loading greatly decreases the impedance in the low humidity range and thus has no effect on improving humidity-sensitive response. Na+-loading increases the sensitive response over four orders of magnitude but causes large hysteresis in the medium humidity range. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{K}^{+}$ </tex-math></inline-formula> -loading raises the sensitive response over four orders of magnitude with a smaller hysteresis loop. Significantly improved humidity performance of a large humidity-sensitive response of nearly five orders of magnitude, satisfactory response/recovery time, low hysteresis, and good linearity were achieved simultaneously by optimizing the ratio of Li+, Na+, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{K}^{+}$ </tex-math></inline-formula> ions. This work underscores that alkaline ion modifying is a facile method to improve the properties of humidity sensors.

A Cellulose Nanofiber Capacitive Humidity Sensor with High Sensitivity and Fast Recovery Characteristics

Humidity sensors with high sensitivity and fast response characteristics are of great interest for researchers. In this work, capacitive humidity sensors were fabricated using ionic liquid/cellulose nanofibers (CNFs) as the composited sensing film. The porous CNFs are beneficial for preparing sensing films via a solution process, and the ionic liquid could be uniformly dispersed in the films. The humidity-sensing performance of the as-prepared sensors was investigated. The optimized sensor showed a high response (27.95 pF/% RH) in a wide humidity range (11–95% RH) and a fast response speed in the adsorption process (the recovery time was only ~1 s). The high response of the sensors was attributed to the polarization at the interface between the electrolyte and the metal electrode, while the fast recovery was due to the rapid desorption of water molecules on the sensing films. Finally, the application of the obtained sensors in human breath monitoring was explored.

Nanodiamond/cellulose nanocrystals composite-based acoustic humidity sensor

This paper fabricated a high-performance nanodiamond (ND)/cellulose nanocrystal (CNC) composite-based acoustic humidity sensor. First, the effects of changes in both mass and viscosity of humidity-sensitive films on the resonance displacement, vibration modes, and impedance characteristics of the quartz crystal microbalance (QCM) were discussed using the finite element simulation software COMSOL Multiphysics. Then, the surface morphology and elemental composition of ND/CNC composites were characterized by TEM and EDS. Next, the humidity-sensing properties of ND/CNC composites, including response sensitivity, humidity hysteresis, dynamic characteristics, and stability, were tested at a relative humidity range from 11.3 % to 97.3 % RH combined with QCM transducers. In addition, the humidity-sensing performance of the QCM sensors with different ratios of composites was compared. The best ND/CNC-based QCM humidity sensors exhibited high sensitivity (54.1 Hz/%RH), low humidity hysteresis (3.2%RH), and fast response/recovery times. Then the adsorption process and sensitivity mechanism of water molecules on ND/CNC composites were analyzed using Langmuir isothermal adsorption model. Finally, the potential application of ND/CNC composite-based QCM humidity sensor was illustrated with respiration monitoring as an example.

High sensitivity portable humidity sensor based on the hydrophilic surface of carbon ring-carbon nitride nanosheets and its wireless application in respiration detection

In this paper, carbon nitride(C3N4) coupled with carbon ring(Cring) with a similar aromatic structure was synthesized by a multi-step-heating method for real-time discrimination of relative humidity(RH) over a broad range of RH(10 %–90 %) at room temperature. Scanning electron microscopy revealed a sheet-like morphology of the as-synthesized sample, consistent with the layered structure observed by XRD analysis. Moreover, the specific surface area of the in-plane heterostructure of Cring-C3N4(68.7 m2g−1) is greater than that of pure g-C3N4(9.1 m2g−1). According to the electrochemical impedance spectroscopy, the introduction of Cring into the C3N4 contributed to the more efficient charge carrier transfer and greatly improved the electrical conductivity. Significant sensing attributes of the sensor, including the response, response/recovery time, hysteresis, repeatability, durability, and selectivity, were evaluated. The test results indicate the significantly enhanced humidity-sensing performance of the Cring-C3N4 sensor in terms of response value(∼416), an utterly reversible sensing process with short response/recovery times(2 s and 3 s, respectively), high stability, and negligible hysteresis compared to pure g-C3N4, a good property for utilization in respiration monitoring. The possible reason for the admirable humidity sensing property can be attributed to the high specific surface area as well as a high proportion of available active sites for water molecules' adsorption and reaction.

CsPbBr3-Based Nanostructures for Room-Temperature Sensing of Volatile Organic Compounds

All-inorganic halide perovskites, as a dominant member of the perovskite family, have been proven to be excellent semiconductors due to the great successes for solar cells, light-emitting diodes, photodetectors, and nanocrystal photocatalysts. Despite the remarkable advances in those fields, there are few research studies focusing on gas and humidity-sensing performances, especially for pure CsPbBr3 and heterogeneous CsPbBr3@MoS2 composites. Here, we first report a valuable CsPbBr3 sensor prepared by electrospinning, and the excellent gas sensing performances are investigated. The CsPbBr3 sensor can quickly and effectively detect ethanolamine at room temperature. The response time is only 16 s, and the response to 100 ppm ethanolamine is as high as 29.87, besides the excellent repeatability and good stability. The theoretical detection limit is estimated to be 21 ppb. Furthermore, considering the irreplaceable role of heterostructures in regulating the electronic structure and supporting rich reaction boundaries, we also actively explored the EA sensitivity of inorganic CsPbBr3-based heterogeneous composites CsPbBr3@MoS2. At the same time, the roles of the critical capping agents OA and OAm are systematically investigated. This work demonstrates the great potential of all-inorganic halide perovskites in promising volatile organic compound detection.

Analysis of the Effect of Electrode Materials on the Sensitivity of Quartz Crystal Microbalance.

This paper investigated the effect of electrode materials on the performance of quartz crystal microbalance (QCM) sensors by means of theoretical calculation, experiment, and finite element analysis methods. First, we calculated the particle displacement amplitude and thus obtained the mass sensitivity function distribution of QCMs with gold, silver and aluminum electrodes, and found that the QCM with the gold electrode has the highest mass sensitivity at the center of the electrode. Then, we tested the humidity-sensing performance of QCMs with gold, silver, and aluminum electrodes using graphene oxide (GO) as the sensitive material, and found that the QCM with the gold electrode has higher humidity sensitivity. Finally, we used the finite element analysis software COMSOL Multiphysics to simulate the specific electrode material parameters that affect the sensitivity of the QCMs. The simulation results show that the density and Young’s modulus of the electrode material parameters mainly affect the sensitivity. The results of this paper are instructive for optimizing QCM sensor performance and improving the capability of QCM quantitative analysis.

Humidity Sensing Ceria Thin-Films.

Lowering the constitutive domains of semiconducting oxides to the nano-range has recently opened up the possibility of added benefit in the research area of sensing materials, in terms both of greater specific surface area and pore volume. Among such nanomaterials, ceria has attracted much attention; therefore, we chemically derived homogeneous ceria nanoparticle slurries. One set of samples was tape-casted onto a conducting glass substrate to form thin-films of various thicknesses, thereby avoiding demanding reaction conditions typical of physical depositions, while the other was pressed into pellets. Structural and microstructural features, along with electrical properties and derivative humidity-sensing performance of ceria thin-films and powders pressed into pellets, were studied in detail. Particular attention was given to solid-state impedance spectroscopy (SS-IS), under controlled relative humidity (RH) from 30%–85%, in a wide temperature and frequency range. Moreover, for the thin-film setup, measurements were performed in surface-mode and cross-section-mode. From the results, we extrapolated the influence of composition on relative humidity, the role of configuration and thin-film thickness on electrical properties, and derivative humidity-sensing performance. The structural analysis and depth profiling both point to monophasic crystalline ceria. Microstructure analysis reveals slightly agglomerated spherical particles and thin-films with low surface roughness. Under controlled humidity, the shape of the conductivity spectrum stays the same along with an increase in RH, and a notable shift to higher conductivity values. The relaxation is slow, as the thickness of the pellet slows the return of conductivity values. The increase in humidity has a positive effect on the overall DC conductivity, similar to the temperature effect for semiconducting behavior. As for the surface measurement setup, the thin-film thickness impacts the shape of the spectra and electrical processes. The surface measurement setup turns out to be more sensitive to relative humidity changes, emphasized with higher RH, along with an increase in thin-film thickness. The moisture directly affects the conductivity spectra in the dispersion part, i.e., on the localized short-range charge carriers. Moisture sensitivity is a reversible process for thin-film samples, in contrast to pellet form samples.

The Effect of Surface Hydroxyls on the Humidity-Sensitive Properties of LiCl-Doped ZnSn(OH)6 Sphere-Based Sensors.

Pure zinc hydroxystannate (ZnSn(OH)6) and LiCl-doped ZnSn(OH)6 have been synthesized through a facile wet chemical method. The LiCl-doped samples keep their original spherical morphology as pure ZnSn(OH)6, with some LiCl particles stuck to its surface, providing more active sites for the adsorption and desorption of water molecules. The influence of LiCl doping on the humidity-sensing properties was explored by varying the dopant concentration. The 16 wt% LiCl/ZnSn(OH)6 showed a better humidity-sensing performance than that of the pure ZnSn(OH)6 and other doped samples, including a high resistive sensitivity, a relatively small hysteresis, and a fast response speed. Through the FTIR analysis, the number of hydroxyl groups on the surface structure after aging has been found to decline markedly. These hydroxyl groups provide a platform for the adsorption of water molecules on the surface and promote the dissociation of water molecules. The detriment of aging to sensor performance should not be underrated. The complex impedance spectrum explains the mechanism of the sensor. These results demonstrate that ZnSn(OH)6 has potential application in fabricating humidity sensors, and the sensing performance of the sensor is enhanced by the dopant LiCl.

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

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.