Effect of Pd²⁺ doping on ZnO nanotetrapods ammonia sensor

Pd²⁺ doped ZnO nanotetrapods were prepared and studied for the detection of ammonia. The gas sensors developed were featured by combination of a quartz crystal as a transducer and Pd²⁺ doped ZnO nanotetrapods as a sensing element. The ZnO nanotetrapods were synthesized by evaporating highly pure zinc pellets (99.999%) at 900°C in air and PdCl₂ was doped on by traditional solution mixing process. Then the mixed solution distributed onto the electrode surfaces of the quartz crystal at room temperature. Pd ²⁺ doped ZnO nanotetrapods were characterized by scanning electron microscopy (SEM). The experimental results indicated that the response of the sensors varied with the different dosage PdCl₂. Pd²⁺ doped ZnO nanotetrapods showed high sensitivity to ammonia in the range of 30-1000 ppm. The response time of the sensor was as fast as ∼2 s at any concentration (40-1000 ppm) of ammonia gas. The Pd²⁺ doped ZnO nanotetrapods coated sensors have a good frequency stability and reproducibility.