Controllably fabricated single microwires from Pd-WO3•xH2O nanoparticles by femtosecond laser for faster response ammonia sensors at room temperature

Micro/nanoscale gas sensors attracted more attention because of their potential application in the emerging areas such as electronic capsules, wearable devices, and microdrone detectors. However, it is still a challenge to achieve micro/nanoscale sensors with controllable processing parameters of active components and fast response and recovery capability. Here, a flexible and high precision femtosecond laser direct-writing technology is selected to print various semiconductor metal oxides nanoparticles into microscale designable patterns with mask-free. And by using Pd-doped WO3•xH2O nanoparticles we have fabricated single Pd-WO3•xH2O microwire (SPWM) as gas sensors, which represented high sensitivity, faster response and recovery. Especially, for ammonia gas sensing the SPWM with pre-designed lengths can possess ultrafast response with response/recovery time of 1.4/3.3 s in 50 ppm NH3, or low limit-of-detection of 1 ppm at room temperature. This kind of micro-scale gas sensor is expected to be applied to human health monitoring, environmental air detection and other integrated intelligent devices.