Photoelectrochemical synthesis, optical properties and plasmon-induced charge separation behaviour of gold nanodumbbells on TiO₂.

Chemically synthesized, commercially available Au nanorods were adsorbed on a TiO₂ thin film, and photoelectrochemically transformed to Au nanodumbbells by photoelectrochemical deposition of Au at both ends of the NRs under UV irradiation. The nanodumbbells show about fourfold greater light absorption than the nanorods based on localized surface plasmon resonance (LSPR) in the visible to near infrared region. The absorption intensities and wavelengths of the Au nanodumbbells depend on the size of their spheroidal caps, which can be controlled by UV exposure time. The nanodumbbells can be applied to LSPR sensors, as their absorption peak redshifts with increasing local refractive index near the metal surface. The Au nanodumbbells on TiO₂ are also suitable for photofunctional materials and devices based on plasmon-induced charge separation (PICS) at the Au-TiO₂ interface, because of their higher photoabsorption intensity, better wavelength tunability and greater PICS efficiency than nanorods.