Morphology controlled fabrication of zinc phosphate hierarchical microspheres for room temperature ammonia gas sensor

• Uniform and novel micro/nanostructures of crystalline zinc phosphate were prepared without using any kind of template/shape directing agents. • Synthesized zinc phosphate nanostructures were employed for fabrication of gas sensors ZP1, ZP2 & ZP3. • ZP1 sensor showed the highest response of 89 % with shortest response recovery times of 31/12 s towards 5 ppm ammonia at room temperature. While the response of other sensors was in the order ZP2> ZP3. • The detection limit revealed to be <1 ppm for the fabricated zinc phosphate based sensors. • The fabricated sensors possess the potential to be used in the ambient where ammonia detection is of major concern for the personnel working. Hierarchical Zinc phosphate nano/microstructures with controlled morphological features were synthesized in aqueous solutions through simple and economical route without using any type of surfactant or template. SEM analysis revealed novel morphologies of the synthesized powders i.e., hierarchical microspheres, urchin like microspheres, nanoflowers and nanoellipsoids and unfolded that produced morphologies strongly depended upon the applied experimental conditions. Selected batches of the synthesized powders i.e., hierarchical microspheres, urchin like microspheres and hierarchical nanoellipsoids were selected for further analysis using XRD, FT-IR, BET analysis and gas sensing application and termed as Zinc Phosphate 1 (ZP1), Zinc Phosphate 2 (ZP2), and Zinc Phosphate 3 (ZP3), respectively. XRD results confirmed the crystalline nature of the as-prepared powders with crystallite sizes 16.5 nm, 30. 15 nm and 37.01 nm, for ZP1, ZP2 and ZP3, respectively. Evaluation of gas sensing properties of the selected samples revealed that sensors based on ZP1 showed highest gas sensing response of 89 % with response recovery time 31/12 s, towards 5 ppm ammonia at room temperature. In addition, the lowest detection limit was investigated to be <1 ppm. Because of the excellent gas sensing performance, the synthesized zinc phosphate structures could be employed as promising candidates for developing highly sensitive and selective room temperature ammonia gas sensor.