Ultrafast Response UV-Regulated Graphene-Based NO2 Gas Sensor

Abstract

In this study, we developed a UV-regulated graphene-based NO₂ gas sensor using high-quality graphene synthesized via chemical vapor deposition (CVD) and fabricated through micro-nano processing techniques. To explore the fundamental sensing mechanism, we conducted measurements under high-purity nitrogen conditions, which revealed that UV illumination raises the Fermi level of graphene, thereby enhancing the adsorption energy and enabling ultrafast NO₂ response. By combining a simple kinetic model with density functional theory (DFT)-calculated adsorption energies for differently doped graphene, we quantitatively link the adsorption energy to the relaxation time and thereby rationalize how UV-induced Fermi-level modulation accelerates the NO₂ adsorption-desorption dynamics. Building upon this mechanistic insight, we further validated the sensor's performance under laboratory air conditions.The sensor demonstrated a rapid room-temperature response to NO₂ over the concentrations range of 0.1-5 ppm, with response times below 5 s, and achieved a 1 s response time at 100 ppb. It also exhibited excellent stability, maintaining consistent responsivity over 638 days and during 100 consecutive tests, with reliable operation under relative humidity (RH) levels up to 75%. Moreover, selectivity tests showed a pronounced response to NO₂ and negligible responses to various common interfering gases even at much higher concentrations. These results highlight the sensor's potential for practical, real-time NO₂ monitoring and offer a new approach for achieving fast gas detection through optoelectronic modulation of graphene.