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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
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
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
Smart things & femtocells : from hype to reality
This book provides a comprehensive overview for the use of femtocells in smart Internet of Things (IoT) environments. Femtocells will help mobile operators to provide a basis for the next generation of services which are a combination of voice, video, and data services to mobile users. This book discusses modelling traffic and deployment strategies in femtocells and provides a review for the use of femtocells and their applications in IoT environments. Moreover, it highlights the efficient real-time medium access, data delivery, caching and security aspects in smart spaces. It concludes by presenting open research issues associated with smart IoT-femtocell based applications-- 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
