Picking Out Hazardous Gases With Light, Not Heat [Reading Science]

KRISS Develops Low-Power LED-Based "Electronic Nose" Gas Sensor

A next-generation sensor technology that can distinguish different types of gases using only light, breaking away from conventional methods that had to be maintained at high temperatures to detect hazardous gases, has been developed by a Korean research team. The technology reduces power consumption while expanding the range of applications, and is expected to enhance gas safety in both industrial sites and everyday environments.

On February 11, the Korea Research Institute of Standards and Science (KRISS) announced that it has developed a gas sensor technology that can precisely identify various types of hazardous gases using inexpensive and safe visible-light LEDs. Unlike conventional gas sensors that operate at high temperatures, this technology works at room temperature, resulting in low power consumption and advantages in terms of sensor lifetime and versatility.

Schematic of an LED-based multi-gas identification sensor developed by KRISS. A Type-I heterojunction structure based on metal oxides and sulfides (In2O3-In2S3) significantly enhances blue LED absorption efficiency and surface reactivity. By combining noble metal catalysts such as palladium, platinum, and gold, KRISS implemented a sensor array capable of selectively distinguishing nitrogen dioxide, ammonia, hydrogen, and ethanol. Provided by KRISS.

Gas sensors widely used in industrial settings today must be kept at high temperatures of 200 to 400 degrees Celsius to increase reactivity with gas molecules. In this process, a micro-heater has to be operated continuously, which leads to high power consumption, and repeated exposure to high heat causes rapid degradation of the sensor materials.

Approaches that use light instead of heaters have also been proposed, but ultraviolet-based sensors pose risks of human exposure, and visible-light LED-based sensors have low reactivity, which limits the types of gases they can detect.

To overcome these limitations, the research team designed a "Type-I heterojunction" nanostructure by thinly coating indium sulfide (In2S3) on indium oxide (In2O3). This structure acts as an "energy well" that concentrates charges generated under illumination onto the reactive surface, thereby inducing an immediate reaction with gas molecules using only blue LED light, without any separate heat source.

In addition, by arranging sensors incorporating different noble metal catalysts such as platinum (Pt), palladium (Pd), and gold (Au), the team implemented an "electronic nose (E-nose)" function that can distinguish multiple gases simultaneously. As a result, hazardous gases such as hydrogen, ammonia, and ethanol could be clearly identified even in mixed environments.

Schematic of the Type-I heterojunction structure developed by KRISS. Under blue LED illumination, the Type-I heterojunction acts like an energy well, collecting charges at the surface and greatly enhancing the sensor surface reactivity at room temperature without a high-temperature heater. Provided by KRISS

In performance tests, the limit of detection reached 201 ppt (parts per trillion, one trillionth), with sensitivity improved by about 56 times compared with existing visible-light LED sensors. The sensor operated stably even under 80% humidity, and its durability was verified by maintaining its initial performance in long-term evaluations over more than 300 days.

Because this technology can identify multiple gases with a single sensor, it can reduce the cost of building sensor networks in industrial sites such as factories and power plants. Its low power consumption and low maintenance costs also make it suitable for expansion into real-time air-quality management systems in residential facilities and public spaces. Thanks to its room-temperature operation, it also has strong potential for use in everyday safety technologies, such as integration into smartphones and wearable devices.

Kwon Gichang, principal researcher of the Advanced Materials Metrology Group at KRISS, who led the study, said, "We plan to further develop this into an intelligent sensor that can selectively detect hazardous gases required for each industrial site by optimizing the combination of catalysts in the future."

This research was carried out with support from the Nano and Materials Technology Development Program of the Ministry of Science and ICT, and the results were published in December last year in Small, an international academic journal in the field of nanotechnology and sensors.