Chirality on nanoscopic surfaces can now be seen using optical microscopy.

The pharmaceutical industry uses chiral surfaces to separate chiral molecules (that differ from their own mirror images), so studying their adsorption and assembly have become fruitful areas of research.

So far, techniques to study chiral surfaces using polarised light have only been carried out on large areas and characterising surfaces at the sub-micrometre scale has been limited. Now, a technique to do just that, using polarised near-field scanning optical microscopy (NSOM), has been developed by Yitzhak Mastai and colleagues from Bar-Ilan University in Israel.

NSOM allows optical microscopy of a higher resolution, beyond the diffraction limit, suitable for nanostructured environments. Mastai's technique was able to distinguish between enantiomerically pure L- and D-histidine crystals grown on gold surfaces with dimensions of 10 micrometres.

In the future, polarised NSOM could be used to identify chirality in a variety of environments, and to measure interactions between drug small molecules and chiral surfaces for pharmacological research.

Mastai hopes to improve his technique to measure optical activity at the nanometre scale, and to use NSOM to explore the relationship between the optical activity of chiral surfaces and their crystalline surface properties.

Elinor Richards