The light that bounces off bundles of molecules, called aggregates, can reveal crucial information about the particles that form them, say Canadian scientists.  Understanding these aggregates is important in a wide range of scientific fields from astrophysics to medicine.

Molecular aggregates are all around us.  Held together by weak intermolecular forces, aggregates are a major component of air pollution and affect both the climate and our health.  They are being studied in medicine as drug delivery systems and they are even present in dust clouds in space.

Using infrared spectroscopy, Ruth Signorell and colleagues at the University of British Columbia, Vancouver, studied aggregates in the size range from one micrometre to less than one nanometre.  By combining the experimental data with the results from computer modelling of the aggregates, she discovered important links between the size, shape and architecture of the particles and the properties of the molecules from which they are built.

'Our goals were two-fold: to identify the spectral signatures of intrinsic particle properties and to understand them on a truly microscopic level,' said Signorell.

Martin Suhm, a spectroscopy expert at the University of Göttingen, Germany, said, 'this work shows convincingly how fundamental spectroscopic research in the laboratory, together with realistic simulations, can strengthen our understanding of nanometre-sized matter.'

Signorell plans to extend the studies to other frequency ranges, to build up reference databases for a variety of particulate systems.

Joanne Thomson