Micro- and nano-sensors lie at the heart of critical innovation in fields ranging from medical to environmental sciences. In recent years, there has been a significant improvement in sensor design ...along with the advances in micro- and nano-fabrication technology and the use of newly designed materials, leading to the development of high-performance gas sensors. Advanced micro- and nano-fabrication technology enables miniaturization of these sensors into micro-sized gas sensor arrays while maintaining the sensing performance. These capabilities facilitate the development of miniaturized integrated gas sensor arrays that enhance both sensor sensitivity and selectivity towards various analytes. In the past, several micro- and nano-gas sensors have been proposed and investigated where each type of sensor exhibits various advantages and limitations in sensing resolution, operating power, response, and recovery time. This paper presents an overview of the recent progress made in a wide range of gas-sensing technology. The sensing functionalizing materials, the advanced micro-machining fabrication methods, as well as their constraints on the sensor design, are discussed. The sensors' working mechanisms and their structures and configurations are reviewed. Finally, the future development outlook and the potential applications made feasible by each category of the sensors are discussed.
The highly selective detection of trace gases using transparent sensors at room temperature remains challenging. Herein, transparent nanopatterned chemiresistors composed of aligned 1D Au–SnO2 ...nanofibers, which can detect toxic NO2 gas at room temperature under visible light illumination is reported. Ten straight Au–SnO2 nanofibers are patterned on a glass substrate with transparent electrodes assisted by direct‐write, near‐field electrospinning, whose extremely low coverage of sensing materials (≈0.3%) lead to the high transparency (≈93%) of the sensor. The sensor exhibits a highly selective, sensitive, and reproducible response to sub‐ppm levels of NO2, and its detection limit is as low as 6 ppb. The unique room‐temperature NO2 sensing under visible light emanates from the localized surface plasmonic resonance effect of Au nanoparticles, thereby enabling the design of new transparent oxide‐based gas sensors without external heaters or light sources. The patterning of nanofibers with extremely low coverage provides a general strategy to design diverse compositions of gas sensors, which can facilitate the development of a wide range of new applications in transparent electronics and smart windows wirelessly connected to the Internet of Things.
Transparent and visible light‐activated NO2 sensor that can operate at room temperature is presented. The pattern of Au–SnO2 nanofibers with extremely low coverage fabricated by direct‐write near‐field electrospinning exhibits high transparency (≈93%), ultrahigh response to NO2, and reversible sensing behaviors under visible light or natural sunlight, enabling the ppb‐level monitoring of indoor or outdoor NO2.
Ultralow Power Gas SensorsToxic gases covertly pose significant threats to our everyday lives due to their inert characteristics. In article number 2304555, Jun‐Bo Yoon and co‐workers introduce a ...groundbreaking ultrathin serpentine insulation design for a highly reliable, energy‐efficient gas sensor. Its mechanically resilient structure achieves over 10,000 cycles of operation and withstood temperatures up to 600 °C with negligible degradation, providing valuable insights for energy‐dependent devices.
In article number 2100438, Jong‐Heun Lee and co‐workers report transparent gas sensors composed of aligned one‐dimensional Au–SnO2 nanofibers with extremely low coverage, transparent electrode, and ...glass substrate, which can detect harmful NO2 at room temperature under visible light illumination or natural sunlight. The transparent sensor design enables the unnoticeable installation of gas sensors on windows without external heaters and light sources.
This paper presents an overview of semiconductor materials used in gas sensors, their technology, design, and application. Semiconductor materials include metal oxides, conducting polymers, carbon ...nanotubes, and 2D materials. Metal oxides are most often the first choice due to their ease of fabrication, low cost, high sensitivity, and stability. Some of their disadvantages are low selectivity and high operating temperature. Conducting polymers have the advantage of a low operating temperature and can detect many organic vapors. They are flexible but affected by humidity. Carbon nanotubes are chemically and mechanically stable and are sensitive towards NO and NH
, but need dopants or modifications to sense other gases. Graphene, transition metal chalcogenides, boron nitride, transition metal carbides/nitrides, metal organic frameworks, and metal oxide nanosheets as 2D materials represent gas-sensing materials of the future, especially in medical devices, such as breath sensing. This overview covers the most used semiconducting materials in gas sensing, their synthesis methods and morphology, especially oxide nanostructures, heterostructures, and 2D materials, as well as sensor technology and design, application in advance electronic circuits and systems, and research challenges from the perspective of emerging technologies.
Abstract
The demand for LPG (Liquefied Petroleum Gas) detection constitutes a major and critical problem in the field of gas detection. LPG is used for domestic appliances used in the heating of ...buildings, producing petrochemicals and as a motor fuel. The current paper used the fabricated ZnO, in addition to TGS 813, TGS 2600, TGS 4160, TGS 3870, TGS 822 as semiconductor gas sensors, in varying temperature and load resistance in a prototype setup so as to explore each model’s accuracy for performance prediction for gas detection. The fabricated ZnO gas sensor is used also to detect the LPG. The comparison is done between gas sensors array and the fabricated one from ZnO. The actual results are put in comparison with the empirical algorithms’ predictions. The optimal model is found to be the full quadratic empirical model based on the lowest error with different sensors.
Flexible gas sensors play an indispensable role in diverse applications spanning from environmental monitoring to portable medical electronics. Full wearable gas monitoring system requires the ...collaborative support of high‐performance sensors and miniaturized circuit module, whereas the realization of low power consumption and sustainable measurement is challenging. Here, a self‐powered and reusable all‐in‐one NO2 sensor is proposed by structurally and functionally coupling the sensor to the battery, with ultrahigh sensitivity (1.92%/ppb), linearity (R2 = 0.999), ultralow theoretical detection limit (0.1 ppb), and humidity immunity. This can be attributed to the regulation of the gas reaction route at the molecular level. The addition of amphiphilic zinc trifluoromethanesulfonate (Zn(OTf)2) enables the H2O‐poor inner Helmholtz layer to be constructed at the electrode–gel interface, thereby facilitating the direct charge transfer process of NO2 here. The device is then combined with a well‐designed miniaturized low‐power circuit module with signal conditioning, processing and wireless transmission functions, which can be used as wearable electronics to realize early and remote warning of gas leakage. This study demonstrates a promising way to design a self‐powered, sustainable, and flexible gas sensor with high performance and its corresponding wireless sensing system, providing new insight into the all‐in‐one system of gas detection.
A self‐powered and reusable all‐in‐one NO2 sensor by structurally and functionally coupling the sensor to the battery, with ultrahigh sensitivity (1.92 %/ppb), linearity (R2 = 0.999), ultralow theoretical detection limit (0.1 ppb), and humidity immunity. Combined with a well‐designed miniaturized low‐power circuit module with signal conditioning, processing and wireless transmission functions, the wearable sensor realizes early and remote warning of gas leakage.
Here stretchable, self‐healable, and transparent gas sensors based on salt‐infiltrated hydrogels for high‐performance NO2 sensing in both anaerobic environment and air at room temperature, are ...reported. The salt‐infiltrated hydrogel displays high sensitivity to NO2 (119.9%/ppm), short response and recovery time (29.8 and 41.0 s, respectively), good linearity, low theoretical limit of detection (LOD) of 86 ppt, high selectivity, stability, and conductivity. A new gas sensing mechanism based on redox reactions occurring at the electrode–hydrogel interface is proposed to understand the sensing behaviors. The gas sensing performance of hydrogel is greatly improved by incorporating calcium chloride (CaCl2) in the hydrogel via a facile salt‐infiltration strategy, leading to a higher sensitivity (2.32 times) and much lower LOD (0.06 times). Notably, both the gas sensing ability, conductivity, and mechanical deformability of hydrogels are readily self‐healable after cutting off and reconnection. Such large deformations as 100% strain do not deprive the gas sensing capability, but rather shorten the response and recovery time significantly. The CaCl2‐infiltrated hydrogel shows excellent selectivity of NO2, with good immunity to the interference gases. These results indicate that the salt‐infiltrated hydrogel has great potential for wearable electronics equipped with gas sensing capability in both anaerobic and aerobic environments.
An intrinsically stretchable, self‐healing, transparent, and ion‐conductive hydrogel is utilized to fabricate NO2 gas sensors. The sensing mechanism reveals that the redox reaction of NO2 at the electrode–hydrogel interface induces current variation. The sensor exhibits high sensitivity (119.9%/ppm), ultralow limit of detection (86 ppt), good selectivity. Meanwhile, it can operate in both anaerobic and aerobic environments at room temperature.
•This work proposes a new method for the rapid preparation of MXenes.•It takes only 3 h to etch the MAX phase by the HIUE method to obtain MXene.•Ti3C2Tx etched by the method can be used as an ...effective nanocomposite substrate.•Ti3C2Tx etched by the method show good selectivity and excellent response to NH3.
MXenes are widely studied two-dimensional materials and have been attracting increasing research attention on exploring their applications. However, the preparation for MXene materials is still cumbersome and time-consuming, significantly limiting their utilization. In this work, a high-intensity ultrasonic exfoliation (HIUE) environment is constructed for efficient preparation of the Ti3C2Tx-MXene, which drastically shortens the etching time to 3 h with a yield of more than 90 % after adjusting the temperature, dosage, and ultrasonic power. The delamination of the MXene occurs during etching due to the ultrasound, which promotes the yield of few-layered MXenes of 20 % in one step after centrifuging. The characteristics of the HIUE-prepared MXenes are compared with those obtained by conventional wet etching methods. The feasibility of the proposed HIUE method is further verified by constructing MXene-based nanocomposites and exploring their gas-sensing applications. The as-prepared Ti3C2Tx MXene obtained by the proposed rapid preparation method show good selectivity and an excellent response of 21.1 % to 100 ppm NH3. In contrast, the MXene/MoS2 nanocomposites obtained by the rapid preparation method also exhibit enhanced gas-sensing performance. Such experiments demonstrate the efficiency and the excellent potential for rapid preparation and compositing of MXene-based materials by the proposed HIUE method.
Laser-induced graphene (LIG) has received much attention since it enables simple and rapid synthesis of porous graphene. This work presents a robust direct-write LIG-based gas sensor, which senses ...gases based on thermal conductivity, similar to a katharometer sensor. The gas sensors are fabricated by lasing polyimide substrates with a 10.6 μm CO2 laser to synthesize LIG. This enables the formation of flexible gas sensors which could be incorporated on a variety of surfaces. High surface area and thermal conductivity of the LIG results in rapid response times for all studied gases. The gas sensors are also embedded in cement to form a refractory composite material. These sensors are used to determine composition of various gas mixtures, such as N2 and CO2, which are the most abundant gaseous species in flue gas. Thus, LIG based embeddable sensors could be incorporated in composites to enable electronically functional construction materials.
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