UC San Diego

Titanium oxide is one of the most widely studied materials for photochemical electrodes because of its high photocatalytic activity. 8 nm diameter TiO₂ nanotubes formed by hydrothermal reaction have been fabricated for water splitting applications. To enhanced photoelectrochemical performance, plasmonic Au nanoparticles have been combined to the TiO₂ nanotubes. First, successful distribution and attachment of fine Au nanoparticles on ̃8 nm diameter TiO₂ nanotubes having significantly increased surface area have been demonstrated. Au thin film deposition onto hydrothermally grown TiO₂ nanotube arrays followed by thermal annealing breaks up the Au film into desired, uniformly distributed nanoparticles. Visible light absorption spectra of the gold nanoparticles on TiO₂ nanotubes indicate that the Au nanoparticles are photo-excited due to plasmon resonance, and charge separation is accomplished by the transfer of photoexcited electrons from the gold particle to the TiO₂ conduction band, thereby enhancing photoelectrochemical performance. Second, a 3-D photoelectrode configuration having hydrothermally formed TiO₂ nanotubes on parallel Ti fins has been successfully fabricated. The Ti fin arrays were assembled by simple and facile spot welding of alternately tall and short Ti foil assembly, which provides significantly increased electrode surface area. A tangled forest of nanotubes of TiO₂ was produced on each of the Ti surface on all parallel and straight fin arrays. UV absorption spectra of the TiO₂ nanotubes indicate that the TiO₂ nanotubes are photo-excited due to their photocatalytic activities, and the charge separation is accomplished by the transfer of photoexcited electrons from the TiO₂ nanotubes to the Ti metallic substrate, thereby performing photoelectrochemical reaction. Third, a novel X-Y matrix structured odor-releasing system with an elastomer-based device has been developed. Relatively low cost and compact design of the system may be achieved through the proposed switchable gas-release method. In addition, odor-release measurements with real time data- logging were also developed for model liquid/gas samples, such as ammonia, ethyl alcohol, and isopropyl alcohol, as well as two perfumes. The electrical actuation system enabled on-off switching of gas release