Gas sensors based on multiwall carbon nanotubes decorated with tin oxide nanoclusters

Hybrid nanomaterials based on oxygen plasma treated multiwall carbon nanotubes decorated with tin oxide nanoclusters were synthesised by the precipitation of a SnO2 colloidal suspension in the presence of carbon nanotubes dispersed in the mother solution of precursor tin (II) acetate in a water free acetic acid. TEM analysis revealed that the size of tin oxide nanoclusters anchored at the carbon nanotube sidewalls is about 5 nm. Hybrid nanomaterials with different carbon nanotube to tin oxide ratios were prepared and their gas sensing properties when operated at room temperature and at 150 °C were investigated and compared against the properties of pure tin oxide or pure oxygen plasma treated multiwall carbon nanotube sensors. When an appropriate ratio between the amount of plasma treated nanotubes and tin oxide precursors is employed, hybrid sensors show superior performance in the detection of nitrogen dioxide in the ppb range and carbon monoxide in the low ppm range. Furthermore, these optimised sensors show a significantly reduced moisture cross-sensitivity. Detection mechanisms are discussed.