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Gold nanoparticles -

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Robyn Williams: And so we end as we began, in the west, with some of those jetlagged miners. In
fact a search for gold like no other; nano-gold. Yes, found for the first time in a way that also
dates back to the times of Faraday and Whewell. Here's Rob Hough of CSIRO Exploration and Mining.

Rob Hough: It's very interesting, Faraday found these things in 1850 and found that if you had a
gold chloride solution and reacted it with something that you'd get these gold colloids. They were
used for stained glass windows because the gold nanoparticles make the solution go red. And the
manufacturing industry over the last decade in particular has been having a massive push around
developing gold nanoparticles to use for superconductors because they have really interesting
properties because they're so tiny, they conduct better, they do all kinds of interesting things in
terms of biological applications, so drug delivery systems into the body.

The gold nanoparticles have been shown to find to things like cancer cells and then so the medical
industry has been interested. So we were looking at these things and thinking, well, okay...also if
you look in the natural environment, people have talked about colloidal gold moving around, and
then we looked at those papers and saw that actually nobody has actually seen the stuff. They've
talked about it but not actually seen it. So we decided that we'd go looking for it.

Robyn Williams: Can I just tell you that at the Royal Institution in London, Faraday's colloidal
solution is still there and I saw it last year, and if you go back that's where you can, even now,
come across what he used, the great Michael Faraday. It just shows you, it's so stable. It was kept
there during the refurbishment. Quite fantastic. Okay, so they'd never seen these particles. How
big are they? Are they unbelievably small?

Rob Hough: If we go back a step, we've got a population of gold crystals in this particular sample
that I've been working on where you can actually see it. So I could show it to you now and you'd
see what looks like glitter on this surface and there's loads of it, it's all gold, it's pure gold.
What we did was we're looking at the surfaces of those gold particles, the ones that we can see,
using a high-powered microscope at the University of Western Australia, and that enabled us to look
at the real surface of those crystals. And when we looked there we found this completely separate
population that was...the maximum size of those crystals was about 200 nanometres, and a nanometre
is a thousandth of a thousandth of a millimetre, and the smallest population were around 20
nanometres, which is amazing.

Robyn Williams: And this is occurring naturally?

Rob Hough: This is in the natural environment, actually just south of Southern Cross in Western
Australia in an area where you've got salty ground water, three times the salinity of sea water,
slightly acidic, and that's reacting with a gold deposit to get the gold into solution to form gold
chloride, so the salty water reacts with the gold, and then that forms this colloid. So you start
to get this colloid, and then through evaporation that colloid gets deposited on surfaces and
that's where it actually gets deposited, and that's where this nanoparticulate gold comes from.

Robyn Williams: Getting it free from nature, would that save a million bucks in manufacture?

Rob Hough: I've been asked this a fair bit and it's really interesting...well, could you actually
harvest this population? At the moment we don't think we have the technology or the method,
certainly we haven't worked it out. It might be there somewhere, to pull out that kind of material.
Can you pull it out of the groundwater, for instance, while it's there in the solution or as a
colloid? I'm not sure whether you can. But also, out of the rocks...and people have been asking can
you actually separate out this really, really ultra fine population? We don't have filters or
things like that to do that. So we need to find some other way and I think that's something we'll
work on because we want to be able to go into other environments and go looking for this population
where it might be there as very, very small, very dilute, and how do we actually extract and
isolate that material, and that's something that I think we'll try and do over the next few years.

Robyn Williams: Is this the first time in history that people have found the nanoparticles of gold
occurring naturally?

Rob Hough: Occurring naturally, yes. So, people have gone looking for it and there have been a
couple of papers talking about it as a mechanism of moving gold around, especially during
weathering which is a really important thing in Australia, but not actually found the population
before, not actually been able to really see it. And I think it's a function of the fact that we
have new technologies these days that have come online in the last two or three years that enable
us to see it at those kind of scales, but also to be able to see surfaces like we haven't been able
to see before, and that's why we've been able to see it.

Robyn Williams: They used to tell me way back that in ordinary sea water you get tiny, tiny amounts
of gold occurring, but of course it's far too expensive to extract that on dilution scales that
occur in the sea. With the new technology it might, who knows.

Rob Hough: I think it's there in very, very low concentrations, and if you go looking like, say, in
the ground waters of Western Australia around gold deposits, then we find reasonable levels of gold
actually in the water. When I say 'reasonable levels' we're still at the parts per billion, parts
per trillion type levels, but we consider those something that's...sometimes they're quite high.
And we use that as an exploration tool because if you find a really, really high number you'd say,
well, where's that gold coming from? It's probably coming from a gold deposit that's weathering
nearby. So there's still plenty of gold out there, it's just a question of finding it. And one of
the challenges that we have is increasingly it's more difficult to find new gold deposits and so we
need these new methodologies, these new understandings to actually be able to go looking in more
complex environments, more complex terrains to find deposits.

Robyn Williams: All those applications that you mention from super conductivity, the miracles of
electronics and the medical applications, how does gold actually have an effect as it does at that

Rob Hough: I think it's really interesting because it's a metal and so it has some really
interesting properties in terms of physical and chemical properties anyway, and all that's
happening is that when you're down at those scales things are reacting far more than they would at
coarser scales and you have a really high surface area from having what looks like a small solution
but in actual fact the amount of surface that's in there in real terms, because you've got all
these tiny, tiny particles means that it's very, very reactive. So gold is a lot more reactive than
people would think it is, because everybody thinks of gold as something that's just inert, doesn't
really change over time, whereas in actual fact it has some really interesting properties, which
means that it does behave differently.

Robyn Williams: Rob Hough in the west with CSIRO Exploration and Mining and with nano-gold, hope
you find some.