Fluorescent semiconductor nanoparticles that exhibit circular dichroism have been made by scientists from Ireland.

Chirality is an important factor in molecular recognition, so the development of a nanosized probe with chiral luminescence would be useful in chemistry and biology. By stabilizing cadmium sulfide nanoparticles, or quantum dots (QDs), with penicillamine a team of scientists, led by Yurii Gun'ko at Trinity College, Dublin, believe they have done just that.

Gun'ko's team prepared the chiral CdS QDs by heating the naked QDs with either left- or right-handed forms (enantiomers) of penicillamine. These gave off a bright green-white light when excited with UV light. When a fifty-fifty (racemic) mixture of the two enantiomers was used, the QDs gave off a bright blue-white light instead.

Circular dichroism studies (used to distinguish between left- and right-handed circular polarised light) found that while the racemic QDs displayed only a weak signal, the right- and left-handed QDs rotated light in opposite directions, producing almost symmetric signals. This would allow the QDs to be used as fluorescent chemical and biochemical chirality sensors, and in molecular recognition nanodevices.

Paul O'Brien of the University of Manchester, UK, was enthusiastic about Gun'ko's work, and said 'producing chiral quantum dots is an exciting development that could lead to a host of new applications in chiral probes and even electronics'.

Gun'ko agreed, saying, 'chiral QDs could find important potential applications in the pharmaceutical industry, asymmetric catalysis, bio-analytical technologies and in vitro medical diagnostics.'

Vikki Chapman