Abstract
A fully integrated photoacoustic nitrogen dioxide (NO2) sensor is developed and demonstrated. In this sensor, an embedded photoacoustic cell was manufactured by using an up-to-date 3D printing technique. A blue laser diode was used as a light source for excitation of photoacoustic wave in the photoacoustic cell. The photoacoustic wave is detected by a sensitive microelectromechanical system (MEMS) microphone. Homemade circuits are integrated into the sensor for laser diode driving and signal processing. The sensor was calibrated by using a chemiluminescence NO–NO2–NOX gas analyzer. And the performance of this sensor was evaluated. The linear relationship between photoacoustic signals and NO2 concentrations was verified in a range of below 202 ppb. The limit of detection was determined to 0.86 ppb with an integration time of 1 s. The corresponding normalized noise equivalent absorption was 2.0 × 10−8 cm−1∙W∙Hz−1/2. The stability and the optimal integration time were evaluated with an Allan deviation analysis, from which a detection limit of 0.25 ppb at the optimal integration time of 240 s was obtained. The sensor was used to measure outdoor air and the results agree with that obtained from the NO–NO2–NOX gas analyzer. The low-cost and portable photoacoustic NO2 sensor has a potential application for atmospheric NO2 monitoring.
Highlights
As one of the main air pollutants, nitrogen dioxide (NO2 ) is mainly produced in engine combustion processes
In addition to delivering direct effects, the existence of NO2 promotes the formation of acidic aerosols, which are strongly harmful to buildings and pedestrians, and leads to the rising of the ozone level near the ground [1]
To monitor this level of NO2 and locating the sources of pollution, a compact, sensitive and low-cost sensor is urgently needed to detect the concentration of NO2
Summary
As one of the main air pollutants, nitrogen dioxide (NO2 ) is mainly produced in engine combustion processes. In addition to delivering direct effects, the existence of NO2 promotes the formation of acidic aerosols, which are strongly harmful to buildings and pedestrians, and leads to the rising of the ozone level near the ground [1]. The Ambient Air Quality Standards in P.R. China sets the safety limit to average 40 μg·m−3 annually and average 200 μg·m−3 hourly. The equivalent volume fraction is about 21 ppb and 106 ppb under 25 ◦ C and standard ambient air pressure. To monitor this level of NO2 and locating the sources of pollution, a compact, sensitive and low-cost sensor is urgently needed to detect the concentration of NO2
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