Molybdenum Trioxide (α-MoO3) Nanoribbons for Ultrasensitive Ammonia (NH3) Gas Detection: Integrated Experimental and Density Functional Theory Simulation Studies

A highly-sensitive ammonia (NH3) gas sensor based on molybdenum trioxide nanoribbons was developed in this study. α-MoO3 nanoribbons (MoO3 NRs) were successfully synthesized via a hydrothermal method and systematically characterized using various advanced technologies. Following a simple drop-cast process, a high-performance chemiresistive NH3 sensor was fabricated through the deposition of a MoO3 NR sensing film onto Au interdigitated electrodes. At an optimal operation temperature of 450 °C, the MoO3 nanoribbon-based sensor exhibited an excellent sensitivity (0.72) at NH3 concentration as low as 50 ppb, a fast response time of 21 s, good stability and reproducibility, and impressive selectivity against the interfering gases such as H2, NO2, and O2. More importantly, the sensor represents a remarkable limit of detection of 280 ppt (calculated based on a signal-to-noise ratio of 3), which makes the as-prepared MoO3 NR sensor the most sensitive NH3 sensor in the literature. Moreover, density functional theory (DFT) simulations were employed to understand the adsorption energetics and electronic structures and thus shed light on the fundamentals of sensing performance. The enhanced sensitivity for NH3 is explicitly discussed and explained by the remarkable band structure modification because of the NH3 adsorption at the oxygen vacancy site on α-MoO3 nanoribbons. These results verify that hydrothermally grown MoO3 nanoribbons are a promising sensing material for enhanced NH3 gas monitoring.