The increase in harmful gas emissions, such as NOx, CO, and H2S for example, is a threat to public health given its negative impact on the human respiratory system even at low concentrations. This invention is a sensitive and selective sensor for NOx gas using SnO (stannous oxide) micro disks as the sensor element. The gas sensor could be used by automotive companies to accurately monitor vehicle NOx emissions and government agencies could monitor air quality in cities and emissions from chemical, petrochemical, and power plants.
Detection of these pollutant gases at ppm and ppb levels, with high sensitivity and selectivity, remains a major challenge. Existing gas detecting technologies based on optical, gravimetric, and electrical approaches are too expensive and require complicated designs.
This technology is based on monitoring changes in resistance of semiconducting oxides upon surface adsorption/desorption of gases. This approach is simple yet cost efficient. The technology consists of SnO micro disks as detection devices for NOx gas. The sensor element, stannous oxide, synthesized by a carbothermal reduction process, which is a facile production method enabling high productivity. Additionally, the disks are prepared from tin dioxide and carbon, both of which are abundant and inexpensive.The device is easily able to detect 100ppb per hour, a standard set by the U.S. Environmental Protection Agency. Additionally, the sensor response for NOx is 200-fold larger than for H2 and CO, and nearly 1000-fold larger than CH4, demonstrating high sensitivity and great selectivity to potential interferents. These disks also have a fast response time, on the order of seconds, making them appropriate for commercial sensors, and presented great stability and reproducibility, allowing them to be produced using inexpensive and well developed technology.
- Simple in design and measurement
- Low cost processing
- High sensitivity