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Room Temperature NHsub.3 Selective Gas Sensors Based on Double-Shell Hierarchical SnOsub.2@polyaniline Composites
Morphology and structure play a crucial role in influencing the performance of gas sensors. Hollow structures, in particular, not only increase the specific surface area of the material but also enhance the collision frequency of gases within the shell, and have been studied in depth in the field of gas sensing. Taking SnO[sub.2] as an illustrative example, a dual-shell structure SnO[sub.2] (D-SnO[sub.2]) was prepared. D-SnO[sub.2]@Polyaniline (PANI) (DSPx, x represents D-SnO[sub.2] molar content) composites were synthesized via the in situ oxidative polymerization method, and simultaneously deposited onto a polyethylene terephthalate (PET) substrate to fabricate an electrode-free, flexible sensor. The impact of the SnO[sub.2] content on the sensing performance of the DSPx-based sensor for NH[sub.3] detection at room temperature was discussed. The results showed that the response of a 20 mol% D-SnO[sub.2]@PANI (DSP20) sensor to 100 ppm NH[sub.3] at room temperature is 37.92, which is 5.1 times higher than that of a pristine PANI sensor. Moreover, the DSP20 sensor demonstrated a rapid response and recovery rate at the concentration of 10 ppm NH[sub.3], with response and recovery times of 182 s and 86 s.
Journal Article
Highly Sensitive and Selective Defect WSsub.2 Chemical Sensor for Detecting HCHO Toxic Gases
The gas sensitivity of the W defect in WS[sub.2] (V[sub.W]/WS[sub.2]) to five toxic gases—HCHO, CH[sub.4], CH[sub.3]HO, CH[sub.3]OH, and CH[sub.3]CH[sub.3]—has been examined in this article. These five gases were adsorbed on the V[sub.W]/WS[sub.2] surface, and the band, density of state (DOS), charge density difference (CDD), work function (W), current–voltage (I–V) characteristic, and sensitivity of adsorption systems were determined. Interestingly, for HCHO-V[sub.W]/WS[sub.2], the energy level contribution of HCHO is closer to the Fermi level, the charge transfer (B) is the largest (0.104 e), the increase in W is more obvious than other adsorption systems, the slope of the I–V characteristic changes more obviously, and the calculated sensitivity is the highest. To sum up, V[sub.W]/WS[sub.2] is more sensitive to HCHO. In conclusion, V[sub.W]/WS[sub.2] has a great deal of promise for producing HCHO chemical sensors due to its high sensitivity and selectivity for HCHO, which can aid in the precise and efficient detection of toxic gases.
Journal Article
Towards a Miniaturized Photoacoustic Sensor for Transcutaneous COsub.2 Monitoring
A photoacoustic sensor system (PAS) intended for carbon dioxide (CO[sub.2]) blood gas detection is presented. The development focuses on a photoacoustic (PA) sensor based on the so-called two-chamber principle, i.e., comprising a measuring cell and a detection chamber. The aim is the reliable continuous monitoring of transcutaneous CO[sub.2] values, which is very important, for example, in intensive care unit patient monitoring. An infrared light-emitting diode (LED) with an emission peak wavelength at 4.3 µm was used as a light source. A micro-electro-mechanical system (MEMS) microphone and the target gas CO[sub.2] are inside a hermetically sealed detection chamber for selective target gas detection. Based on conducted simulations and measurement results in a laboratory setup, a miniaturized PA CO[sub.2] sensor with an absorption path length of 2.0 mm and a diameter of 3.0 mm was developed for the investigation of cross-sensitivities, detection limit, and signal stability and was compared to a commercial infrared CO[sub.2] sensor with a similar measurement range. The achieved detection limit of the presented PA CO[sub.2] sensor during laboratory tests is 1 vol. % CO[sub.2]. Compared to the commercial sensor, our PA sensor showed less influences of humidity and oxygen on the detected signal and a faster response and recovery time. Finally, the developed sensor system was fixed to the skin of a test person, and an arterialization time of 181 min could be determined.
Journal Article
Smart Gas Sensors: Recent Developments and Future Prospective
Highlights
Recent developments of advanced electronic and optoelectronic gas sensors are introduced.
Sensor array with artificial intelligence algorithms and smart gas sensors in “Internet of Things” paradigm are highlighted.
Applications of smart gas sensors in environmental monitoring, medical and healthcare applications, food quality control, and public safety are described.
Gas sensor is an indispensable part of modern society with wide applications in environmental monitoring, healthcare, food industry, public safety, etc. With the development of sensor technology, wireless communication, smart monitoring terminal, cloud storage/computing technology, and artificial intelligence, smart gas sensors represent the future of gas sensing due to their merits of real-time multifunctional monitoring, early warning function, and intelligent and automated feature. Various electronic and optoelectronic gas sensors have been developed for high-performance smart gas analysis. With the development of smart terminals and the maturity of integrated technology, flexible and wearable gas sensors play an increasing role in gas analysis. This review highlights recent advances of smart gas sensors in diverse applications. The structural components and fundamental principles of electronic and optoelectronic gas sensors are described, and flexible and wearable gas sensor devices are highlighted. Moreover, sensor array with artificial intelligence algorithms and smart gas sensors in “Internet of Things” paradigm are introduced. Finally, the challenges and perspectives of smart gas sensors are discussed regarding the future need of gas sensors for smart city and healthy living.
Journal Article
Artificial intelligence techniques in IoT-sensor networks
\"Artificial Intelligence Techniques in IoT-Sensor Networks is a technical book which can be read by researchers, academicians, students and professionals interested in Artificial Intelligence (AI), Sensor Networks and Internet of Things (IoT). This book intends to develop a shared understanding of applications of AI techniques in the present and near term. The book maps the technical impacts of AI technologies, applications, and their implications on the design of solutions for sensor networks\"-- Provided by publisher.
Book
Rapid and Efficient NOsub.2 Sensing Performance of TeOsub.2 Nanowires
Gas sensors play a pivotal role in environmental monitoring, with NO[sub.2] sensors standing out due to their exceptional selectivity and sensitivity. Yet, a prevalent challenge remains: the prolonged recovery time of many sensors, often spanning hundreds of seconds, compromises efficiency and undermines the precision of continuous detection. This paper introduces an efficient NO[sub.2] sensor using TeO[sub.2] nanowires, offering significantly reduced recovery times. The TeO[sub.2] nanowires, prepared through a straightforward thermal oxidation process, exhibit a unique yet smooth surface. The structural characterizations confirm the formation of pure-phase TeO[sub.2] after the anneal oxidation. TeO[sub.2] nanowires are extremely sensitive to NO[sub.2] gas, and the maximum response (defined as the ratio of resistance in the air to that under the target gas) to NO[sub.2] (10 ppm) is 1.559. In addition, TeO[sub.2] nanowire-based sensors can return to the initial state in about 6–7 s at 100 °C. The high sensitivity can be attributed to the length–diameter rate, which adsorbs more NO[sub.2] to facilitate the electron transfer. The fast recovery is due to the smooth surface without pores on TeO[sub.2] nanowires, which may release NO[sub.2] quickly after stopping the gas supply. The present approach for sensing TeO[sub.2] nanowires can be extended to other sensor systems as an efficient, accurate, and low-priced tactic to enhance sensor performance.
Journal Article