Sandia's shell collection
8 Sep 2003
Synthetic crystals with structures similar to seashells could form the basis of a new generation of industrial devices, say their developers at Sandia National Laboratory.
The US government-funded research centre in Albuquerque, New Mexico, is trying to find ways of controlling the formation of the crystals to produce the shapes and structures - and, therefore the properties - they need.
The range of possibilities for the nanostructured crystals is vast. The team believes that, depending on the materials used, they could find applications in catalysis, chemical and biological sensing for industrial and medical uses, in microelectronic devices, and in energy conversion and storage, such as in photovoltaic cells, batteries, capacitors and hydrogen storage devices for fuel cells. Still more possible applications include drug delivery devices, light-emitting display components, and optical storage media.
'We have already demonstrated superior photocatalytic properties and new chemical sensor devices with our new materials,' says Jun Liu, the manager of Sandia's Department of Chemical Synthesis and Nanomaterials.
In nature, the formation of shell-like structures is mediated by protein molecules, whose structure controls both the formation of the shell mineral, which can be composed of several different crystals of the same substance, and how they are deposited. This isn't possible in the lab, because the roles of the different types of proteins are not understood. Liu's task is to find simple organic molecules that can perform the same directing task under mild conditions - low temperatures, low concentrations of chemicals, and using aqueous solutions rather than organic solvents.
The team uses techniques such as surface modification of substrates and nanoparticles as crystal nucleation seeds to control how minerals form into their shell-like structures. Lab-on-a-chip technology such as microfluidic devices are used to control the reactions.
'The microfluidic studies may also lead to the methods for the continuous manufacturing of tailored nanoscale materials, including nanoparticles, nanowires, and complex nanostructured films,' Liu says.
