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III Nitrides for Gas Sensing Applications
Published in Ankur Gupta, Mahesh Kumar, Rajeev Kumar Singh, Shantanu Bhattacharya, Gas Sensors, 2023
A chemiresistor is a material that changes its electrical resistance in response to a change in concentration of gaseous species. A simple two-terminal device can be manufactured to monitor the resistance change in the semiconductor. This is a surface phenomenon which involves the participation of the target gases in physisorption followed by chemisorption processes on the surface. Oxygen plays an important role in such reaction by chemisorbing on the surface as O O2−,O−orO2− depending on the ambient temperature [16,17]. If a reducing gas such as H2 or NH3 reacts with these species, they release back an electron into the conduction band of the material which reduces the resistance of the material. For an oxidizing gas, the resistance increases by a similar mechanism. In the absence of oxygen, the mechanism is trickier though a reaction-based mechanism also observed for oxidizing gases could also occur.
Smart farming
Published in Govind Singh Patel, Amrita Rai, Nripendra Narayan Das, R. P. Singh, Smart Agriculture, 2021
Kanwaljeet Singh, Amandeep Kaur
MQ-2, the grove gas sensor is mainly used to detect leakage of gas from home and industry. It can detect different gases like H2, CH4, LPG, CO, alcohol, smoke and propane. It is very fast in taking actions because it has very high sensitivity and very fast response time. It is a metal oxide semiconductor gas sensor and also known as chemiresistor because gas detection is done by measuring change in resistance when gas comes in contact with sensor material. To detect different concentrations of gas, voltage divider network can be used. This sensor works on 5 V DC proper supply. The MQ-2 sensor has total six pins, where four pins are used for signal fetching and two for current conduction.
Electrochemical Sensors
Published in John Vetelino, Aravind Reghu, Introduction to Sensors, 2017
If a conductimetric sensor uses a film other than a metal oxide semiconductor, it is usually referred to as a chemiresistor. The films that are typically used in the chemiresistor include organic films and metallic films.
A DFT Based Approach for NO2 Sensing Using Vander Wall Hetero Monolayer
Published in IETE Journal of Research, 2023
Suman Sarkar, Papiya Debnath, Debashis De, Manash Chanda
Mainly, optical [5], electrochemical [6], and chemiresistor types [7] sensing mechanisms are reported for NO2. An optical method [5] is highly sensitive as it works on basis of chemiluminescent emission and infrared light absorption wavelengths of NO2 gas molecules. However, these are bulky and not cost-effective [7,8]. In an electrochemical sensor [6], electrochemical reduction of NO2 is performed in the presence of noble catalysts. This is a low-cost process [9] but the operation lifetime is very short [10]. The common mechanism of the chemiresistor sensor is based on the principle of charge sharing between the sensor and gas molecule (NO2) [11,12] which may change the electrochemical properties of the sensor. Among these three, the chemiresistor is found to be suitable because of its low cost and compact sensor size. However, the semi-metallic, semiconducting material with low bandgap, such as C3N [13], germane [14], phosphorene [15], graphene [16], silicone [17], arsenene [18], as mentioned in Table 1, have been studied widely for sensing NO2. Recently, the sensitivity of wideband semiconductor-based gas sensors also has been studied [19], as mentioned in Table 1. However, sensing property often can be improved by doping [20] as mentioned in Table 1 and introduction of some defects. Group III-V element can also be used to develop high quality gas sensor because of excellent electronics properties.The calculated value of adsorbed energy (Ead), Interatomic bond length d(Å), and charge transfer between adsorbed and adsorbent Q(e) is given on Table 1.