In a significant stride towards enhancing gas sensing technology, researchers at the Academy of Innovative Semiconductor and Sustainable Manufacturing at National Cheng Kung University in Taiwan have developed a novel nitrogen dioxide (NO2) gas sensor with remarkable sensitivity and selectivity. Led by Mu-Ju Wu, the team’s findings, published in the journal ‘Applied Surface Science Advances’ (translated as ‘Advances in Surface Science and Applications’), could have profound implications for environmental monitoring and industrial safety, particularly in the energy sector.
The research team initially focused on indium oxide (In2O3) sensing membranes, prepared using a magnetron radio frequency (RF) sputtering system and annealed in a hydrogen atmosphere. They discovered that annealing the films at 400 °C for 10 minutes created more oxygen vacancies, which in turn provided more gas adsorption sites. “This enhancement in oxygen vacancies is crucial as it directly correlates with the sensor’s ability to detect gas more effectively,” explained Wu.
To further improve the sensor’s performance, the team doped the In2O3 membranes with zinc (Zn), creating In2O3:Zn sensing membranes. The optimal concentration of Zn was found to be 5.4 atomic percent, which yielded a response of 66.0 under a 10-ppm NO2 concentration. The team then deposited these membranes on various periodic nanoimprinted nanorod array patterns, with the 400-nm-periodic pattern showing the best results, achieving a response of 94.4 under the same NO2 concentration.
The breakthrough came when the researchers decorated the In2O3:Zn sensing membranes with p-type gold-black nanoparticles (NPs), forming p-n heterojunctions. This innovation significantly enhanced the sensor’s performance. “The combination of gold-black nanoparticles and In2O3:Zn sensing membranes resulted in a sensor that could detect NO2 concentrations as low as 0.1 ppm and exhibited high selectivity towards NO2 gas,” said Wu. Under a NO2 concentration of 10 ppm, the gas sensors achieved a maximum response of 141.5 at an operating temperature of 115 °C.
The implications of this research for the energy sector are substantial. NO2 is a critical pollutant emitted by combustion processes, and its accurate detection is vital for environmental monitoring and industrial safety. The enhanced sensitivity and selectivity of these new sensors could lead to better emission control and improved air quality management. Moreover, the low operating temperature and high response rate make these sensors ideal for real-time monitoring applications.
This study not only advances the field of gas sensing technology but also opens up new avenues for research into the use of nanoimprinted patterns and p-n heterojunctions in sensor design. As Wu noted, “Our findings could pave the way for the development of more advanced and efficient gas sensors, benefiting various industries and contributing to a safer and more sustainable future.”
The research was published in ‘Applied Surface Science Advances’, a journal dedicated to the rapid publication of high-quality research in the field of surface science and its applications. The team’s work is a testament to the ongoing innovation in materials science and its potential to drive technological advancements in the energy sector.