Nano-Biotechnology

A Golden Technology for Cleansing the Air

A new method employing manganese oxide and gold, much more effective

By Stefan Anitei, Science Editor

2nd of April 2007, 09:55 GMT

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Besides non-organic molecules like nitrogen oxides and sulfur oxides, many volatile organic compounds (VOCs) in air are implicated in smog and high ozone levels, and are potentially harmful for human health, that's why clean-air laws are turning increasingly stricter.

Current air-purification systems work with photocatalysts, adsorbents like activated charcoal, or ozonolysis, methods that are less effective on destroying organic pollutants at room temperature.

But now, a Japanese team has developed a new material which is very effective in eliminating VOCs, besides nitrogen- and sulfur oxides,

at room temperature.

The new device uses a highly porous manganese oxide garnished with gold nanoparticles grown into it.

The Japanese team led by Anil K. Sinha at the Toyota Central R&D Labs carried out experiments with acetaldehyde, toluene, and hexane to show the effectiveness of the new material.

These are one of the three major organic air contaminants, both outside and indoors.

All three of these contaminants were very effectively removed from air and degraded by the catalyst, much better than with conventional catalyst systems.

The key to the higher effectiveness of this novel material is the extremely large inner surface induced by the porous manganese oxide, which is much larger than all previously known manganese oxide forms.

The extremely expanded surface area gives the volatile compounds a large number of adsorption sites and the adsorbed contaminants are very effectively destroyed.

And the manganese oxide lattice presents plenty of oxygen available for oxidation processes.

Surface degradation is highly effective as free radicals are present there.

Presumably, oxygen from air dissociates on the gold surface to replace the consumed oxygen atoms in the lattice structure.

But to achieve the right material, a very specific method is required: the gold must be put onto the manganese oxide by employing vacuum-UV laser ablation.

This technique means a gold surface is irradiated with a special laser, which removes gold particles through evaporation.

The removed gold particles possess unusually high energy, which enables them to move relatively deep into the surface of the manganese oxide.

This is the only method to produce enough strong interactions between the little gold structure and the manganese oxide support.

TAGS:

gold | contamination | catalyst | manganese

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