Improving light absorbing properties of titanium oxide and iron has led researchers from Brookhaven National Laboratory to develop hitherto unknown nano-formulations, that might have applications for clinical medicine:
The research is published in two papers now available online, one in Advanced Materials (August 22, 2007), and the other in the Journal of Physical Chemistry (September 8, 2007).
In the first study, the scientists enhanced the ability of titanium oxide to absorb light.
“Titanium dioxide’s ability to absorb light is one the main reasons it is so useful in industrial and medical applications,” said Wei-Qiang Han, a scientist at Brookhaven’s Center for Functional Nanomaterials…
Many scientists have explored ways to improve the light-absorbing capability of titanium oxide, for example, by “doping” the material with added metals. Han and his coworkers took a new approach. They enhanced the material’s light-absorption capability by simply introducing nanocavities, completely enclosed pockets measuring billionths of a meter within the 100-nanometer-diameter solid titanium oxide rods.
The resulting nanocavity-filled titanium oxide nanorods were 25 percent more efficient at absorbing certain wavelengths of ultraviolet A (UVA) and ultraviolet B (UVB) solar radiation than titanium oxide without nanocavities.
“Our research demonstrates that titanium oxide nanorods with nanocavities can dramatically improve the absorption of UVA and UVB solar radiation, and thus are ideal new materials for sunscreen,” Han said.
The cavity-filled nanorods could also improve the efficiency of photovoltaic solar cells and be used as catalysts for splitting water and also in the water-gas-shift reaction to produce pure hydrogen gas from carbon monoxide and water.
The method for making the cavity-filled rods is simple, says Han. “We simply heat titanate nanorods in air. This process evaporates water, transforming titanate to titanium oxide, leaving very densely spaced, regular, polyhedral nanoholes inside the titanium oxide.”
In the second paper, Han and his collaborators describe a new synthesis method to make iron-doped titanate nanotubes, hollow tubes measuring approximately 10 nanometers in diameter and up to one micrometer (one millionth of a meter) long. These experiments were also aimed at improving the material’s photoreactivity. The scientists demonstrated that the resulting nanotubes exhibited noticeable reactivity in the water-gas-shift reaction.