Au nanoparticle decoration of nanoparticular and nanotubular TiO2 using atmospheric pressure cold plasma for photocatalytic applications†

Herein, we present the effectiveness of using an atmospheric pressure dielectric barrier discharge (DBD) plasma torch for gold (Au) nanoparticle (NP) decoration of TiO₂ nanoparticles and nanotubes (NTs). Au NPs were synthesised using an aerosol of HAuCl₄·3H₂O solution that was carried with an inert gas to the near plasma post-discharge zone. Careful optimisation of the deposition parameters was done to ensure the uniform and dispersed decoration of TiO₂, demonstrated by scanning and transmission electron microscopy with energy dispersive spectroscopy. The X-ray diffraction was used to confirm that the deposit was pure metallic Au. Unlike the bare TiO₂ nanoparticles, the samples with Au NPs showed the plasmon resonance peak in the region of 500–600 nm. The photocatalytic property enhancement of Au NP decorated TiO₂ structures was demonstrated: The TiO₂ NPs@Au nanoparticular powder showed improved photocatalytic activity by enabling methyl orange dye degradation 35% faster than that of the pristine TiO₂ NPs; superior photocatalytic behaviour of TiO₂ NTs@Au thin films compared to bare TiO₂ NTs was observed in the photodegradation of stearic acid.