Micro-light-emitting diodes (μLEDs) have garnered significant interest as light sources for gas sensors due to their advantages, such as room temperature operation and low power consumption. However, despite these benefits, challenges remain, including a limited range of detectable gases and slow response times.
To address this, a research team including Inkyu Park from the Korea Advanced Institute of Science and Technology (KAIST), Sang-Wan Ryu from Chonnam National University, and Ho Won Jang from Seoul National University, developed a blue μLED-integrated gas sensor array based on SnO 2 nanoparticles (NPs). This array exhibits excellent sensitivity, tunable selectivity, and rapid detection with microwatt-level power consumption.
Using the finite-difference time-domain (FDTD) method, Inkyu Park and colleagues simulated the light absorption of SnO 2 nanoparticles under varying light intensities. By assuming a densely packed spherical structure of SnO 2 NPs, they obtained simulated absorption distributions along the z-axis under light intensities of 50, 200, and 500 mW cm -2 . At lower light intensities, the lowest layer of SnO 2 NPs was fully activated and reacted with NO 2 . Since the number of photogenerated carriers was far less than the molar quantity of NO 2 , all carriers reacted with NO 2 molecules. As the light intensity increased, more layers of SnO 2 NPs became activated, leading to a greater number of NO 2 molecules reacting. Once the activated layers matched the thickness of the sensor’s electrode, the sensor’s response peaked. However, when the activation depth of SnO 2 NPs exceeded the electrode thickness due to excessive light intensity, the sensor’s response diminished. Upon introducing NO 2 , most molecules reacted with SnO 2 NPs on the top layer, resulting in increased resistance in the upper layers, with the lower layers experiencing only a slight increase. Consequently, the majority of the current passed through the lower layers, which had lower resistance, leading to a reduced sensor response. Across these stages, the response curve exhibited a volcano-like pattern with respect to light intensity, highlighting the synergistic effects of the SnO 2 material properties and sensor device architecture on gas-sensing performance.
Furthermore, the gas-sensing performance of Au-SnO 2 NPs, Pd-SnO 2 NPs, and Pt-SnO 2 NPs towards NO 2 was studied under light exposure. Compared to SnO2 NPs, the response to 5 ppm of NO 2 decreased for Au-SnO 2 NPs, Pd-SnO 2 NPs, and Pt-SnO 2 NPs, with Pt-SnO 2 NPs showing the most significant reduction. When the reducing gases NH 3 , CO, H 2 , C 2 H 5 OH, and CH 3 COCH 3 were tested under blue light, all sensors displayed distinct selectivity patterns. Polarization diagrams of SnO 2 NPs, Au-SnO 2 NPs, Pd-SnO 2 NPs, and Pt-SnO 2 NPs toward the reducing gases revealed that SnO 2 NPs showed moderate responses to NH 3 , CO, and C 2 H₅OH, while Au-SnO 2 NPs exhibited high sensitivity and selectivity to C 2 H 5 OH. Pd-SnO 2 NPs responded well to H 2 , and Pt-SnO 2 NPs displayed strong responses to various gases, particularly NH 3 . In summary, noble-metal-modified SnO 2 NP-based gas sensor arrays demonstrated the ability to distinguish a wide variety of gases under light illumination. This work is expected to advance μLED-based gas sensors, expanding the range of detectable gases and contributing to healthier living environments.
Nano-Micro Letters
Experimental study
Real-Time Tunable Gas Sensing Platform Based on SnO2 Nanoparticles Activated by Blue Micro-Light-Emitting Diodes
8-Aug-2024