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Functional Nanomaterial-Based Gas Sensors and Humidity Sensors

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A special issue of Chemosensors (ISSN 2227-9040). This special issue belongs to the section "Materials for Chemical Sensing".

Deadline for manuscript submissions: 31 August 2025 | Viewed by 15387

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Dr. Zaihua Duan

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Guest Editor

State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu 611731, China
Interests: gas sensor; humidity sensor; pressure sensor; strain sensor; sensing functional material

Special Issue Information

Dear Colleagues,

With the rapid development of information technology, sensors, as the source of information acquisition, play an irreplaceable role. Among them, gas sensors and humidity sensors used for gas and humidity detection have received widespread attention in recent years, and they have important applications in industrial, agricultural, and atmospheric detection fields. In addition, gas sensors and humidity sensors have shown promising application prospects in the human body (such as exhaled gas composition, respiratory status, skin humidity, non-contact switches, and baby diaper detection).

Although gas sensors and humidity sensors have made tremendous progress, they still face many challenges; for example, their performances need to be improved (including sensitivity, detection range, response speed, and stability), and in addition to detecting environmental gases and humidity, their applications in human body detection need further development. With the development of various functional nanomaterials, it is necessary to address the challenges faced by gas sensors and humidity sensors. This Special Issue of Chemosensors will focus on recent research papers as well as review articles for advanced gas sensors and humidity sensors and their various applications in the environment and the human body.

Dr. Zaihua Duan
Guest Editor

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Keywords

gas sensors
humidity sensors
flexible humidity sensors
functional nanomaterials
novel sensing materials
environment detection
non-invasive breath gas analysis
human-body-related humidity detection
wearable applications

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Published Papers (10 papers)

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Research

Jump to: Review

15 pages, 4254 KiB

Open AccessArticle

Analysis of the Application of Cryptophane-A\-E in a Mass-Sensing Methane Gas Sensor: Insights from a Numerical Simulation

by Xinlei Liu, Dan Xiao, Qinglan Zhang, Yu Guan, Bin Shen and Jiazhe Li

Chemosensors 2025, 13(5), 179; https://doi.org/10.3390/chemosensors13050179 - 12 May 2025

Viewed by 237

Abstract

Supramolecular compounds are capable of encapsulating small molecules to form host–guest compounds, which can be combined with sound surface wave technology to achieve high-precision detection of specific gases. In this paper, we analyzed the adsorption ability of Cryptophane-A and Cryptophane-E, the caged supramolecular materials, at room temperature by numerical simulation using first principles. The geometrical optimization of Cryptophane-A, Cryptophane-E, and gas molecules was carried out by the Dmol³ module in Materials Studio. Through adsorption calculation of gas molecules, the change of density of states and the magnitude of adsorption energy of Cryptophane-A and E were compared and analyzed. The results show that Cryptophane-A and E are van der Waals adsorption for molecules in gas (except CO₂ and C₂H₆). The adsorption energy of Cryptophane-A is lower than that of Cryptophane-E, but it is more selective and has preferential adsorption for methane. In this paper, we also tried to calculate the adsorption of Cryptophane-A and E on two methane molecules. The result showed that the former could adsorb two methane molecules, but the adsorption energy was lower than that of one methane molecule; the latter could not adsorb two methane molecules stably. The study shows that Cryptophane-A is more suitable as a sensitive material for CH₄ detection, which provides support for the development of acoustic surface wave methane detection technology. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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16 pages, 5244 KiB

Open AccessArticle

The Sensing Selectivity of Gas Sensors Based on Different Sn-Doped Indium Oxide Films

by Haoran Sheng, Haoyu Li, Yujie Huang, Bochao Zhang, Jiarui Liang, Xinze Zhou, Yuan Tian and Qiang Li

Chemosensors 2025, 13(5), 169; https://doi.org/10.3390/chemosensors13050169 - 5 May 2025

Viewed by 241

Abstract

The gas-sensitive performance and selectivity of gas sensors via different Sn-doped indium oxide (In₂O₃) films have been investigated. The response characteristics were significantly enhanced to methanol (CH₄O), ethanol (C₂H₆O), and acetone (C₃H₆O) with the increase in Sn content, while the response time and the recovery time became shorter. The sensor exhibited the strongest response to ethanol, followed by acetone and then methanol with all the ratios of In₂O₃ (90%, 85%, and 80%) and SnO₂ (10%, 15%, and 20%). The mechanism of Sn doping on the gas sensing selectivity was calculated using the density functional theory (DFT) method, which perfectly explained the experimental results. The sensors demonstrated high selectivity towards ethanol, even in the presence of interfering gases. In addition, the sensors showed effective detection of the target gas with 10 ppb and demonstrated good repeatability. This work systematically analyzed the priority selectivity of In₂O₃-based gas sensors, providing a new path for gas detection in multi-interference and complex environments. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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15 pages, 4178 KiB

Open AccessArticle

A Stable and Fast-Response Multifunctional Humidity Sensor Based on a Polyanionic Liquid Containing Bromide Ions

by Shiqi Zhang, Chenghong Wei, Li Li, Jincan Cui, Xiaolei Yuan, Dandan Hao and Heng Wang

Chemosensors 2025, 13(3), 79; https://doi.org/10.3390/chemosensors13030079 - 1 Mar 2025

Viewed by 585

Abstract

Humidity sensors are widely utilized in meteorological research, industrial production, precision instrument maintenance, agriculture, health care, and other fields. However, the long response time and low sensitivity of current metal oxide and hybrid humidity sensors limit their practical applications. In this study, a humidity sensor was prepared using a simple drop-casting method with 2-hydroxy-2-methylpropiophenone (HOMPP) and 1-vinyl-3-butylimidazolium bromide (C₉H₁₅BrN₂) as the humidity sensing materials. This approach offers advantages such as low cost, high chemisorption capacity, and excellent moisture-sensitive performance. The prepared humidity sensors demonstrate high sensitivity, good repeatability, excellent flexibility, low hysteresis, and response/recovery times of 6/12.5 s, respectively, over a wide relative humidity (RH) range (2–97%). Additionally, the sensor exhibits potential for various multifunctional applications, including humidity detection in daily life, respiratory monitoring, non-contact sensing, and flexible electronics applications. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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21 pages, 7403 KiB

Open AccessArticle

Low-Temperature, Highly Sensitive Ammonia Sensors Based on Nanostructured Copper Iodide Layers

by Sergey I. Petrushenko, Mateusz Fijalkowski, Kinga Adach, Denis Fedonenko, Yevhenii M. Shepotko, Sergei V. Dukarov, Volodymyr M. Sukhov, Alina L. Khrypunova and Natalja P. Klochko

Chemosensors 2025, 13(2), 29; https://doi.org/10.3390/chemosensors13020029 - 22 Jan 2025

Cited by 2 | Viewed by 1005

Abstract

Chemiresistive ammonia gas sensors with a low limit of detection of 0.15 ppm and moisture-independent characteristics based on p-type copper iodide (CuI) semiconductor films have been developed. CuI films were deposited on glass and polyethylene terephthalate (PET) substrates using a Successive Ionic Layer Adsorption and Reaction method to fabricate CuI/glass and CuI/PET gas sensors, respectively. They have a nanoscale morphology, an excess iodine and sulfur impurity content, a zinc blende γ-CuI crystal structure with a grain size of ~34 nm and an optical band gap of about 2.95 eV. The high selective sensitivity of both sensors to NH₃ is explained by the formation of the [Cu(NH₃)₂]⁺ complex. At 5 °C, the responses to 3 ppm ammonia in air in terms of the relative resistance change were 24.5 for the CuI/glass gas sensor and 28 for the CuI/PET gas sensor, with short response times of 50 s to 210 s and recovery times of 10–70 s. The sensors have a fast response–recovery and their performance was well maintained after long-term stability testing for 45 days. After 1000 repeated bends of the flexible CuI/PET gas sensor in different directions, with bending angles up to 180° and curvature radii up to 0.25 cm, the response changes were only 3%. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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15 pages, 4984 KiB

Open AccessArticle

Fast-Response Hydrogen Sensor Based on γ-Al₂O₃-Modified Graphene

by Bin Shen, Qinglan Zhang, Xinlei Liu, Jiazhe Li, Yu Guan and Dan Xiao

Chemosensors 2024, 12(12), 250; https://doi.org/10.3390/chemosensors12120250 - 28 Nov 2024

Viewed by 955

Abstract

The fast response of H₂ sensors plays an important role in the early warning of H₂ leakage; in this work, a nanoscale

γ

-Al₂O₃ carrier material was prepared using the precipitation method and a new hydrogen sensor was [...] Read more.

The fast response of H₂ sensors plays an important role in the early warning of H₂ leakage; in this work, a nanoscale

γ

-Al₂O₃ carrier material was prepared using the precipitation method and a new hydrogen sensor was prepared by doping and modifying it with graphene. During the detecting part of the experiment, the voltage–current–temperature detecting system was designed based on the principle of voltage division and shunt, and the theoretical operating temperature computational model was established in parallel. After testing, it was shown that the sensor had a good linear relationship for the range of 1000–10,000 ppm H₂; the operating temperature was only 176 °C at 1.4 V operating voltage, the T₉₀ response time was 6.69 s, and the average sensitivity and temperature rise characteristics were 28.23 mV/1% H₂ and 36.77 °C/1% H₂, respectively. Moreover, the calculated theoretical operating temperature and the measured temperature were basically consistent. This work provides a useful reference for further exploration of H₂ sensors. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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15 pages, 3476 KiB

Open AccessArticle

Flexible Humidity Sensor Based on Chemically Reduced Graphene Oxide

by Anna Maria Laera, Gennaro Cassano, Emiliano Burresi, Maria Lucia Protopapa and Michele Penza

Chemosensors 2024, 12(12), 245; https://doi.org/10.3390/chemosensors12120245 - 22 Nov 2024

Cited by 1 | Viewed by 1172

Abstract

The accurate measurement of moisture content in pure gases and in gas mixtures, such as air, has great relevance in many industrial processes. In the present study, graphene oxide reduced through a mild alkaline treatment was used as a humidity sensing material to fabricate a flexible chemiresistive device operating at room temperature. The active layer was deposited by solution casting on a substrate of bimatted polyester, previously coated with inkjet-printed interdigitated electrodes made of silver. Structural investigations were performed by means of X-ray diffraction, Raman spectroscopy, and FTIR spectroscopy, while the optical properties were investigated using UV-VIS absorption and photoluminescence excitation spectroscopy. With increasing relative hu-midity from 0 to 80%, the electrical resistance decreased from about 1.4 GΩ to 2.5 MΩ. The ex-traordinarily large range of resistance values highlights the ultrahigh humidity sensitivity of re-duced graphene oxide, which acquires a fair amount of electrical conductivity after physisorption of water molecules but results in a highly resistive material in dry air. The high sensitivity at room temperature, the response’s repeatability, the wide relative humidity range detected, and the fast response time are the main advantages of the proposed humidity sensor, while the presence of some hysteresis, mainly at low relative humidity, and the recovery time need further improve-ment. Finally, the sensing mechanisms are briefly discussed. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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14 pages, 7204 KiB

Open AccessArticle

Optimization by Hydrogen Plasma Treatment of a-CH and Hydrogen/Nitrogen-Assisted a-CH Layers for SAW Sensors

by Veronica Satulu, Mihai Paunica, Simona Brajnicov, Sorin Vizireanu, Gheorghe Dinescu, Bogdana Mitu and Cristian Viespe

Chemosensors 2024, 12(9), 194; https://doi.org/10.3390/chemosensors12090194 - 20 Sep 2024

Viewed by 3571

Abstract

The high toxicity of hydrogen sulfide combined with poor sensitivity at room operating temperature urge for the development of new sensitive materials for sensors complying with this requirement, as well as a fast response and low cost. In this work, we have successfully developed materials for surface acoustic wave (SAW) sensors sensitive to H₂S gas that provide a reversible response at room temperature. The sensitive materials were created by plasma-enhanced chemical vapor deposition of a-CH films using methane as a precursor with argon and argon admixed with hydrogen or nitrogen and applied on piezoelectric quartz substrates. Smooth films, with an AFM root mean square below 1.5 nm, were obtained in all cases, although slight topographical variations were noted, depending on the gas types. XPS detected varying degrees of oxidation, indicating that the assisting gases played a crucial role in introducing oxygen-containing functional groups, thus influencing the material’s surface chemistry and sensitivity response. A hydrogen plasma treatment was applied on the a-CH deposited sensors as a further sensor preparation step. The hydrogen plasma treatment resulted in significant modifications in the topographical features, including roughness increase and notable variations in the surface aspect ratios, as confirmed through AFM data analysis, which involved advanced pixel height analysis and line profile processing. X-ray photoelectron spectroscopy (XPS) studies indicated the formation of new functional groups, increased defect density, and a significant reduction in electron transitions following hydrogen plasma treatment. The sensors demonstrated a reversible response to H₂S gas within 8 to 20 ppm concentration ranges, effectively detecting these levels. The sensitivity of the sensors was significantly enhanced, up to 39% through hydrogen plasma treatment, reaching an improved overall performance in detecting low concentrations of H₂S down to 0.9 ppm. These findings highlight a-CH thin films as an excellent candidate for next-generation SAW sensors. The study also suggests the potential for experimenting with various assisting gases during plasma deposition and additional plasma treatments to push detection capabilities to below ppm levels. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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13 pages, 2553 KiB

Open AccessArticle

Carbon-Based FET-Type Gas Sensor for the Detection of ppb-Level Benzene at Room Temperature

by Risheng Cao, Zhengyu Lu, Jinyong Hu and Yong Zhang

Chemosensors 2024, 12(9), 179; https://doi.org/10.3390/chemosensors12090179 - 4 Sep 2024

Cited by 2 | Viewed by 1618

Abstract

Benzene, as a typical toxic gas and carcinogen, is an important detection object in the field of environmental monitoring. However, it remains challenging for the conventional resistance-type gas sensor to effectively detect low-concentration (ppb-level) benzene gas molecules, owing to their insufficient reaction activation energy, especially when operating at room temperature. Herein, a field-effect transistor (FET)-type gas sensor using carbon nanotubes as a channel material is proposed for the efficient detection of trace benzene, where carbon nanotubes (CNTs) with high semiconductor purity act as the main channel material, and ZnO/WS₂ nanocomposites serve as the gate sensitive material. On the basis of the remarkable amplification effect in CNTs-based FET, the proposed gas sensor manifests desirable sensitive ability with the detection limit as low as 500 ppb for benzene even working at room temperature, and the sensor also exhibits fast response speed (90 s), high consistency with a response deviation of less than 5%, and long-term stability of up to 30 days. Furthermore, utilizing Tenax TA as the screening unit, the as-proposed gas sensor can achieve the feasible selective detection of benzene. These experimental results demonstrate that the strategy proposed here can provide significant guidance for the development of high-performance gas sensors to detect trace benzene gas at room temperature. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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21 pages, 4181 KiB

Open AccessArticle

Detection of Harmful H₂S Concentration Range, Health Classification, and Lifespan Prediction of CH₄ Sensor Arrays in Marine Environments

by Kai Zhang, Yongwei Zhang, Jian Wu, Tao Wang, Wenkai Jiang, Min Zeng and Zhi Yang

Chemosensors 2024, 12(9), 172; https://doi.org/10.3390/chemosensors12090172 - 29 Aug 2024

Viewed by 1424

Abstract

Underwater methane (CH₄) detection technology is of great significance to the leakage monitoring and location of marine natural gas transportation pipelines, the exploration of submarine hydrothermal activity, and the monitoring of submarine volcanic activity. In order to improve the safety of underwater CH₄ detection mission, it is necessary to study the effect of hydrogen sulfide (H₂S) in leaking CH₄ gas on sensor performance and harmful influence, so as to evaluate the health status and life prediction of underwater CH₄ sensor arrays. In the process of detecting CH₄, the accuracy decreases when H₂S is found in the ocean water. In this study, we proposed an explainable sorted-sparse (ESS) transformer model for concentration interval detection under industrial conditions. The time complexity was decreased to O (n log_n) using an explainable sorted-sparse block. Additionally, we proposed the Ocean X generative pre-trained transformer (GPT) model to achieve the online monitoring of the health of the sensors. The ESS transformer model was embedded in the Ocean X GPT model. When the program satisfied the special instructions, it would jump between models, and the online-monitoring question-answering session would be completed. The accuracy of the online monitoring of system health is equal to that of the ESS transformer model. This Ocean-X-generated model can provide a lot of expert information about sensor array failures and electronic noses by text and speech alone. This model had an accuracy of 0.99, which was superior to related models, including transformer encoder (0.98) and convolutional neural networks (CNN) + support vector machine (SVM) (0.97). The Ocean X GPT model for offline question-and-answer tasks had a high mean accuracy (0.99), which was superior to the related models, including long short-term memory–auto encoder (LSTM–AE) (0.96) and GPT decoder (0.98). Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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Review

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24 pages, 7104 KiB

Open AccessReview

Recent Advances in Metal Oxide Semiconductor Heterojunctions for the Detection of Volatile Organic Compounds

by Shengming Zhang, Heng Zhang, Haiyu Yao, Peijie Wang, Min Zhu, Xuerong Shi and Shusheng Xu

Chemosensors 2024, 12(12), 244; https://doi.org/10.3390/chemosensors12120244 - 22 Nov 2024

Cited by 4 | Viewed by 3583

Abstract

The efficient detection of volatile organic compounds (VOCs) is critically important in the domains of environmental protection, healthcare, and industrial safety. The development of metal oxide semiconductor (MOS) heterojunction gas-sensing materials is considered one of the most effective strategies to enhance sensor performance. This review summarizes and discusses the types of heterojunctions and their working principles, enhancement strategies, preparation methodologies, and applications in acetone and ethanol detection. To address the constraints pertaining to low sensitivity, sluggish response/recovery times, and elevated operating temperatures that are inherent in VOC sensors, several improvement methods are proposed, including doping with metals like Ag and Pd, incorporating additives such as MXene and polyoxometalates, optimizing morphologies through a fine design, and self-doping via oxygen vacancies. Furthermore, this work provides insights into the challenges faced by MOSs heterojunction-based gas sensors and outlines future research directions in this field. This review will contribute to foundational theories to overcome existing bottlenecks in MOS heterojunction technology while promoting its large-scale application in disease screening or agricultural food quality assessments. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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