S o l u ti ons
f or working with
BY LYNN SAVAGE
When creating a new technology – or
tweaking an old one – you always
end up starting from the bottom and
working your way up. No, not your position in the company, the basic nature of
the materials with which you are working.
It doesn’t matter whether you are looking to make a high-efficiency solar collector, artificial neurons or a better mousetrap, you must have as complete an
understanding of the components as possible. Once, that meant having only a good
knowledge of macro materials; now, you
need to know what’s going on at the molecular level.
For the most part, materials research at
this level involves shunting nanoclusters
of molecules, such as cadmium selenide,
or of individual elements, such as silver,
around a flat substrate. Types of this research include quantifying the electro-optical properties of carbon nanotubes and
More recently, scientists have become
interested in how particles of various sorts
operate in aqueous environments, such as
living cells or solutions in which nanoparticles may be formed or other chemical reactions may be induced. Tracking minute
particles in solution (even, in some cases,
as they are precipitating out) can provide
important clues to the dynamics underpinning the device in which the particles
ultimately may be used.
One set of researchers recently reported
that a typical method for preparing samples for inductively coupled plasma optical emission spectroscopy (ICP-OES) has
room for improvement. In ICP-OES – the
gold standard for studying minute particles
in liquid environments – a relatively large
material sample is broken down into tinier
and tinier bits. These particles, sometimes
as small as single molecules, are then
scanned by a probing laser beam for spectroscopic analysis.
A new direction, developed by E.V.
Muravitskaya and her colleagues at B.I.
Stepanov Institute of Physics in Minsk,
Belarus, uses such a laser beam more directly. Because acids or other substances
used to break down a sample typically do
their jobs incompletely, the scientists used
a 1064-nm Q-switched Nd:YAG laser to
ablate their target samples.
They tested their system on several alloys that were alike in composition – comprising zinc, iron, aluminum, copper and
magnesium – but differing in concentration of these elements. They placed samples of the alloys into distilled water and
used the laser to irradiate them with 10- to
12-ns pulses at 10 Hz ( 8 μs between
pulses). Each pulse provided 50 mJ of energy at the sample surface. After 3 s, they
moved the sample to ablate a different
part. After about 80 s, ablation was complete, with the original samples left pitted
and cratered and nanometer-scale particles
clouding the solution. They compared
their laser ablation results with a standard
chemical digestion method as well.
The investigators noted in the February
issue of Spectrochimica Acta Part B that
using laser ablation to divide large particles into a size fit for ICP-OES has several
advantages. First, compared with chemical
erosion, laser ablation does not waste sample material because it more completely
breaks down the mass. Second, ablation
does not cause the suppressive effect that
acids have on signals picked up by the