Detection of ppb-level NO₂ gas using a portable gas-sensing system with a Fe₂O₃/MWCNTs/WO₃ sensor using a pulsed-UV-LED

Abstract

A portable gas-sensing system which is periodically irradiated with light from a pulsed ultraviolet light emitting diode (UV-LED) was fabricated for sensing ppb-level NO2 gas.

Photoactivated materials and sensors for NO2 monitoring

“…The mixture of more than two types of materials base on Fe 2 O 3 -MWCNTs-WO 3 for the photoactivated response to NO 2 was also reported in the past [71], although without a specific mention of the formation and influence of junctions in the sensing properties of the composite films. Laboratory tests of these composite films showed a response of 0.67 % to 50 ppb of NO 2 under pulsed UV illumination (365 nm) and response and recovery times of 232 s and 71 s, respectively.…”

“…The selectivity tests indicated a remarkable response to NO 2 compared to the other gases (NH 3 , SO 2 , CO, and H 2 S). Further tests of these sensors in the exhaust of a motorcycle in the idling position proved their on-field applicability by detecting NO 2 (232 ppb) [71]. The combination of p-n heterojunctions and metal-semiconductor junctions in the same systems was also tested previously by using ZnO-Cu 2 O composite films modified with Au [66].…”

Highly Surface Active Phosphorus-Doped Onion-Like Carbon Nanostructures: Ultrasensitive, Fully Reversible, and Portable NH3 Gas Sensors

“…The sensing performance of developed P-OLCs has been shown to be more advantageous as compared to the existing reports (Table S2). − We highlight the importance of P-OLCs with tunable electronic structures as a novel catalyst-free sensing element, which exhibits a stable and excellent gas sensing performance.…”

Phenylalanine Dipeptide-Regulated Ag/In2O3 Nanocomposites for Enhanced NO2 Gas Sensing at Room Temperature with UV Illumination

“…Among various efforts, semiconducting metal oxide has been popular due to the simplicity of its fabrication and low cost. 4,5 At the time of this study, a growing number of metal oxides have been used in the detection of various gases, such as tin oxide (SnO 2 ), 6−8 titanium dioxide (TiO 2 ), 9,10 tungsten oxide (WO 3 ), 11 vanadium pentoxide (V 2 O 5 ), 12 and zinc oxide (ZnO). 1,13−15 Furthermore, indium oxide (In 2 O 3 ) has the advantage of being able to detect both reducing and oxidizing gases, 16−19 with a high sensitivity and fast response due to its high surface-to-volume ratio for gas species absorption/desorption and low-resistance pathways for charge carrier transport.…”

“…It is a major atmospheric pollutant that can cause serious health damage to humans, such as lung disease. , Therefore, the development of sensing materials for NO 2 sensors is of extreme importance, and, thus, many researchers have attempted to produce these materials. Among various efforts, semiconducting metal oxide has been popular due to the simplicity of its fabrication and low cost. , At the time of this study, a growing number of metal oxides have been used in the detection of various gases, such as tin oxide (SnO 2 ), − titanium dioxide (TiO 2 ), , tungsten oxide (WO 3 ), vanadium pentoxide (V 2 O 5 ), and zinc oxide (ZnO). ,− Furthermore, indium oxide (In 2 O 3 ) has the advantage of being able to detect both reducing and oxidizing gases, − with a high sensitivity and fast response due to its high surface-to-volume ratio for gas species absorption/desorption and low-resistance pathways for charge carrier transport. However, the oxygen molecules on In 2 O 3 surface grab electrons and become adsorbed oxygen (O 2 – , O – , O 2– ) for gas detection, which usually need to be at a temperature of 100–300 °C .…”