Titanium dioxide (TiO2), also known as titania, is a strong photocatalyst that breaks down organic compounds when exposed to light. It is widely used as a coating material for preventing the build-up of dirt, bacteria and organic pollutants on outdoor surfaces. Self-cleaning glass, for example, typically has a thin coating of TiO2.
Of all the different forms of TiO2 coating, TiO2 nanotube arrays have probably the highest photocatalytic activity. The nanotubes in a TiO2 nanotube array are hollow, vertically aligned and densely packed; the ultrathin wall thickness of TiO2 nanotubes and the unique architecture of TiO2 nanotube arrays are some of the major factors contributing to the superior photocatalytic activity. Unfortunately, fabrication of TiO2 nanotube arrays on surfaces is still a significant challenge.
Gao Han and co-workers at the A*STAR Institute of Materials Research and Engineering1 have now fabricated a transparent palladium-functionalized TiO2 nanotube array on a glass substrate. They studied how the photocatalytic activity of the TiO2 nanotube array changes as the wall thickness or height of the nanotubes was adjusted, and identified the nanotube configuration that gave the highest photocatalytic activity.
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