Advanced Materials for Gas Sensors: Performance and Application

Dear Colleagues,

Gas sensors, despite being the subject of research for many years, are still attracting significant attention from the scientific community due to their numerous applications. Indeed, they have become essential in several fields, including environmental monitoring and worker safety, medical care, food quality tracking and industrial processes. Furthermore, gas sensors could play an important role in the Internet of Things (IoT) field, not only from the perspective of smart cities, industries, or homes, but also in wearable health monitoring devices.

For all these applications, market requests are becoming increasingly demanding, especially in terms of detection limit, response and recovery time and sensitivity to low ppm concentration among interfering gases, not to mention cost and energy consumption.

One strategy to address these requirements is the search for new suitable materials, as well as novel functionalization strategies and innovative fabrication processes, which can enhance the sensor performance.

Therefore, the goal of the present Special Issue is to present novel and promising experimental and theoretical approaches in gas sensor and sensor array development exploiting advanced materials. The latest advances in science and technology will be highlighted, including novel high-performance materials with enhanced sensing properties, innovative functionalization techniques and cutting-edge fabrication and processing methods. Works investigating the sensing mechanisms through innovative techniques and from a theoretical point of view are also welcome.

Original research articles (full papers or communications) and reviews are all welcome.

I look forward to receiving your contributions.

Dr. Sonia Freddi
Prof. Dr. Luigi Sangaletti
Guest Editors

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• gas sensors
• chemical sensors
• sensor arrays
• 2D materials
• 1D materials (nanowires, nanotubes, and nanorods)
• functionalization, doping, and heterostructures
• sensing mechanism
• Internet of Things (IoT)
• gas sensors applications (medical care, environmental monitoring, food quality tracking, industrial processes and safety)

Title: Elucidating the Synthesis and Sensing Mechanism of Copper-Doped Nanostructured WS2
Authors: Fatima Ezahra Annanouch； Virginia Pérez-Dieste ；Eduard Llobet； and Carla Bittencourt
Affiliation: 1 Departament d’Enginyeria Electronica, Universitat Rovira i Virgili, Països Catalans 26, 43007 Tarragona, Spain 2 ALBA Synchrotron Light Source, Carrer de la Llum 2-26, 08290 Cerdanyola del Vallès, Spain 3 Chimie des Interactions Plasma Surface, CIRMAP, Université de Mons, Place du Parc 23, 7000 Mons, Belgium
Abstract: Metal oxide semiconductors have been widely used as sensing materials in gas sensors. However, these sensors require high operating temperatures that demand considerable power sourcing, which can be a significant challenge in dispersed networks involving complex sensing systems with a large number of devices. Novel materials that enable low-temperature operation could alleviate power-related challenges and contribute to better and more robust sensor networks. Recent studies have shown that 2D layered transition metal dichalcogenides (TMDs) such as WS2 and MoS2 can be attractive alternatives for chemoresistive sensors, as they offer a substantial response at low operating temperatures with particular selectivity to certain gases such as H2S and NH3. The lowered operation temperature of transition metal chalcogenide-based sensors, in reference to the oxides of the corresponding metals, is due to their typically smaller bandgap and better conductivity. Additionally, the gas selectivity of TMDs is often associated with surface adsorption affinity for different analytes and related surface charging/polarization effects, similar to semiconducting metal oxide sensors. Moreover, reversible doping of the chalcogenide lattice with heteroatoms can significantly contribute to sensing. Despite the fact that many works discuss sensing mechanisms TMDs materials under dry conditions or in the presence of ambient moisture, these are speculative in nature, since operando spectroscopic studies have been scarcely used in these studies. Using Near atmospheric pressure XPS combined with advanced electron microscopy, we study the effect of the morphology and metal oxide loading on the gas sensing mechanism of Cu-WS2. The surface composition and electronic structure of WS2 nanomaterials were analyzed under real conditions. This means, at the sensor operating temperature and during the exposure to CO, and CH4. By identifying the intermediate species adsorbed together with the measurement of electrical conductance, we expect to unveil the morphology-performance relationship in the detection of CO, and CH4. NAP-XPS is a unique technique capable of conducting this type of analysis under realistic operating conditions.