Core-shell structure of polypyrrole grown on W18O49 nanorods for high performance gas sensor operating at room temperature

Abstract In this work, uniform core-shell structure of polypyrrole wrapped on tungsten oxide nanorods (PPy@W 18 O 49 core-shell nanorods) were synthesized via a two-step process for gas-sensing applications. The core-nanorods of W 18 O 49 were first grown by solvothermal method with tungsten hexachloride (WCl 6 ) as precursor. The PPy-shell layer was then formed uniformly on the solvothermally synthesized W 18 O 49 nanorods by in-situ chemical polymerization of pyrrole monomer (Py), with sodium dodecyl benzene sulfonic acid (DBSA) as dopant and ammonium persulfate (APS) as oxidant. High dispersion of Py achieving in ethanol is proved to be crucial to form the uniform PPy-shell layer, and the layer thickness of PPy-shell is highly controlled by adjusting the Py concentration in polymeric solution. The morphology and structure of the nanocomposite were characterized systematically; it shows that the composite exhibits perfect core-shell structure of one-dimensional (1D) nanorods with average diameter of around 70–90 nm. The NH 3 -sensing properties of the sensors based on the PPy@W 18 O 49 core-shell nanorods were investigated at operating temperature of 15–130 °C over NH 3 concentration ranging from 1 to 200 ppm. The response magnitude of the PPy@W 18 O 49 sensor can be affected seriously by temperature fluctuation, even in room temperature range (15–30 °C), and meanwhile, a temperature-dependent p-n response characteristic reversal is observed for the heteronanorods sensor. At much low room temperature of 15 °C, the present PPy@W 18 O 49 nanorods show quick and sensitive response to NH 3 gas mainly due to the ultrathin, uniform PPy shell and the special heterojunction effect between p-type PPy and n-type W 18 O 49 . The underlying gas-sensing mechanism is analyzed.