Fabrication and Computational Study of a Chemiresistive NO₂ Gas Sensor Based on the Carbon Dots-WO₃ Heterostructure for Operating below Room Temperature

Abstract

For a long time, chemiresistive gas sensors based on metal oxide semiconductors (MOSs) suffer from higher operating temperatures, resulting in higher energy consumption and instability of the sensors. Generally, a MOS-based chemiresistive gas sensor being able to work at room temperature is considered to be outstanding already. Here, a highly sensitive NO2 gas sensor based on the carbon dots-WO3 heterostructure, which can work below room temperature at –6 °C, is fabricated. At 18, –1, and –6 °C, its detection limits are 200 ppb, 5 ppm, and 20 ppm, respectively, and the corresponding response values (R a/R g) are 1.11, 1.04, and 1.13, respectively. The sensor exhibits good selectivity, stability, and linearity between relative humidity and response values too. A peculiar response behavior was observed. Toward oxidizing gas NO2, the resistance of the sensor based mainly on n-type WO3 shows decrease behavior. Its peculiar response behavior and strong gas sensing ability at lower temperatures were elucidated theoretically using the results of first-principles calculations. The reduction of NO2 into NO by surface oxygen vacancies of WO3 and the following adsorption of NO on the surface of WO3 lead to electron transfer from NO to WO3, and the Fermi level shifts toward the conduction band, making the sensor exhibit the peculiar response behavior. The stronger adsorption capability of carbon dots toward NO2 and a synergistic effect of carbon dots and WO3 together make the sensor capable of working at lower temperatures and own higher sensitivity.

Adsorption of NO2, NO, NH3, and CO on Noble Metal (Rh, Pd, Ag, Ir, Pt, Au)-Modified Hexagonal Boron Nitride Monolayers: A First-Principles Study

“…As a common gas in industrial production, nitrogen dioxide (NO 2 ) can lead to grave respiratory problems, including inflammation of the trachea and accumulation of fluid in the lungs. − Moreover, recent investigations have shown that NO 2 is closely related to the prevention and transmission of COVID-19. , And it is also a significant account of environmental pollution such as summer smog, acid rain, and PM 2.5, which poses a major endangerment to mankind’s health and the safety of other life on the earth. , According to the OSHA regulations, the maximum concentration of short-term exposure to NO 2 is 5 ppm in industry. Long-term exposure to high concentrations of NO 2 can lead to poor breathing, lung disease, and even death. , Additionally, nitric oxide (NO) is a major contributor to air pollution and can have an unfavorable influence on mankind’s health. It can cause respiratory problems and cardiovascular diseases and result in the formation of smog and particulate matter.…”

“…Long-term exposure to high concentrations of NO 2 can lead to poor breathing, lung disease, and even death. 8,9 Additionally, nitric oxide (NO) is a major contributor to air pollution and can have an unfavorable influence on mankind's health. It can cause respiratory problems and cardiovascular diseases and result in the formation of smog and particulate matter.…”

Ultrasensitive Chemiresistive Sensor for NO2 Based on Oxidation of a Thiophene Polymer Bearing Oligoethylene Glycol Side Chains

“…A chemiresistive NO 2 sensor is a device that detects and quantifies the concentration of nitrogen dioxide gas in the air using a chemiresistive transducer. , The principle of operation involves the change in the electrical resistance of a sensing material upon exposure to NO 2 gas. Conducting polymers (CPs), such as polyaniline, polythiophene, and polypyrrole, are commonly used as sensing materials due to their high sensitivity and selectivity toward NO 2 gas. − The chemiresistive NO 2 sensor has several advantages over other types of sensors, including low power consumption, simple configuration, and high sensitivity. , …”

Handheld Crop Pest Sensor Using Binary Catalyst-Loaded Nano-SnO2 Particles for Oxidative Signal Amplification

“…The ability of the platform to show matching redox activity is the key to improve the sensitivity and selectivity . To achieve this, semiconductors and noble metals having catalytic facets for adsorption/desorption and reactivity , were engineered together for ppb/μM level of detection. , …”

“…15 To achieve this, semiconductors and noble metals having catalytic facets for adsorption/desorption and reactivity 16,17 were engineered together for ppb/μM level of detection. 18,19 According to the Food and Agriculture Organization (FAO), tomato is the second most important vegetable crop after potato. Its wide cultivation makes it susceptible to insect herbivory, especially Tuta absoluta, which is an economically important pest.…”