Pd nanoparticles on SnO2(Sb) whiskers: Aggregation and reactivity in CO detection

• Pd decorated SnO2(Sb) whiskers synthesized by VLS and impregnation methods.
• Pd nanoparticles grow by Volmer–Weber or Stranski–Krastanov mechanisms.
• Sensor signal to CO depends on Pd nanoparticles size and their aggregation degree.

Single crystal antimony-doped SnO2 whiskers have been synthesized by in situ doping process in horizontal flow reactor. The produced whiskers were modified with 0.1, 0.2, 0.5, 1 or 2 wt.% Pd. The processes of Pd particles growth and aggregation are described on the base of AFM and STEM data. Depending on the content of introduced Pd precursor, the various mechanisms (Volmer–Weber or Stranski–Krastanov) of Pd nanoparticles growth realize. The dependence of sensor signal to CO on Pd concentration has non-monotonous character determined by the size of Pd nanoparticles and their aggregation degree. The best sensor signal toward CO was observed for whiskers decorated with 0.1 wt.% Pd. This concentration corresponds to the presence of individual 3–5 nm Pd nanoparticles on the surface of the whiskers.