Impact of Temperature and UV Irradiation on Dynamics of NO2 Sensors Based on ZnO Nanostructures

Abstract

The main object of this study is the improvement of the dynamics of NO2 sensors based on ZnO nanostructures. Investigations presented in this paper showed that the combination of temperature and ultraviolet (UV) activation of the sensors can significantly decrease the sensor response and regeneration times. In comparison with the single activation method (elevated temperature or UV), these times for 1 ppm of NO2 decreased from about 10 min (or more) to less than 40 s. In addition, at the optimal conditions (200 °C and UV), sensors were very stable, were fully scalable (in the range on NO2 concentration of 1–20 ppm) and baseline drift was significantly reduced. Furthermore, in this paper, extensive studies of the influence of temperature and carrier gas (nitrogen and air) on NO2 sensing properties of the ZnO nanostructures were conducted. The NO2 sensing mechanisms of the sensors operating at elevated temperatures and under UV irradiation were also discussed. Our study showed that sensor responses to NO2 and response/regeneration times are comparable from sensor to sensor in air and nitrogen conditions, which suggests that the proposed simple technology connected with well-chosen operation conditions is repeatable. The estimated limit of detection of the sensors is within the level of ≈800 ppb in nitrogen and ≈700 ppb in air.

Laser-induced periodic surface structures on ZnO thin film for high response NO2 detection

“…The responses showed for the sensor processed with LIPSS towards low concentrations of NO 2 are similar or higher compared with other published pure ZnO nanostructured sensors such as [32,22,33]. Al though in the other works, the optimal temperatures are slightly lower than for the sensor with LIPSS, the fabrication techniques require sev eral steps avoided here by the in situ nanostructuring and selectivity is not shown in any of the investigations.…”

“…Due to the changes on the surface structure, defects could be generated at the surface of the semiconductor and consequently a higher response could be expected for specific gases. Besides, the generation of LIPSS with a femtosecond laser presents an important advantage for gas sensing applications since the nanos tructures can be patterned directly on the sensing device (in situ), without the need to transfer them, as it is the case of most of bottom up techniques (ex situ) such electrospinning [21] or hydrothermal [22] methods. On the other hand, this laser technique is able to nanos tructure large surface areas [17], what is an important issue for its application in industrial processes.…”

Study of NO2 Sensing Properties of UV-Activated Graft Comb Copolymer and ZnO Blends in ppm and Sub-ppm Range at Room Temperature

“…The signal change for the CH fraction has been determined and is equal to 9.30% per 1 ppb of NO2, and for H fraction 6,80% per 1 ppb. Compared to our previous work [11], based solely on nanostructural ZnO, the applied sensing layer of an organic polymer (PEGSil) blend with an inorganic structured material (ZnO) significantly improved the parameters of the sensors produced, ranging from effective work at low temperatures (room temperature), through response dynamics and ending with the sensor response value itself (about 20 times greater signal change).…”

“…The organic-inorganic blend was prepared by mixing together conductive graft copolymer with zinc oxide nanomaterial as a suspension for fabricating thin film layer by drop coating method. 1 mg of ZnO obtained by hydrothermal method [10,11] was dispersed in the 5 ml of chlorobenzene using 30 min ultrasonic stirring. 2.5 mg of PEGSil polymer was dissolved in 1 ml of chlorobenzene, using 30 min ultrasonic stirring.…”

Impact of UV radiation on sensing properties of conductive polymer and ZnO blend for NO2 gas sensing at room temperature

“…The measurements were carried out in a gas chamber under N2 as a carrier gas flow in dark conditions and under UV light illumination (LED, λ = 390 nm) and under 1, 5, 10 ppm of NO2 gas. The gas sensing measurement setup is presented in details elsewhere [11]. In all cases we observed a resistance drop of the fabricated sensors, during the reaction with NO2 gas, which is characteristic for a p-type semiconductor.…”