Nerve gas sensor using film bulk acoustic resonator modified with a self-assembled Cu2+/11-mercaptoundecanoic acid bilayer

We present an application of film bulk acoustic resonator for trace nerve gas sensing. The resonator consisted of a piezoelectric Au/AlN/Mo stack and a Bragg reflector has a working resonance near 2.35 GHz and a high performance. A self-assembled composite layer of Cu2+/11-mercaptoundecanoic acid is modified on the Au electrode as a specific coating to capture organophosphorus compounds. The experimental results show that the chemical modified film bulk acoustic resonator can yield a rapid, sensitive, reversible and reproducible response to dimethyl methyl phosphonate (a stimulant of nerve agent) vapor. When the sensitive layer absorbs organophosphorus compounds, the mass loading increases and the resonance frequency proportionally goes down. The chemical modified film bulk acoustic resonator sensor is able to detect dimethyl methyl phosphonate vapor at the concentration as low as 100 ppb. The advantages of this sensor, including the simple fabrication process, ease of detection method, rapid response and high sensitivity, make this promising in the early alarm of nerve agents.