Polymerisation of S2N2 - a new way to see hidden fingerprints

20-Oct-2010 - United Kingdom

Fingerprints that have been washed off surfaces could now be retrieved thanks to a development by scientists in the UK and reported in the Journal of materials chemistry.

The strained four-membered ring system, S2N2 quickly polymerises to (SN)x in the presence of fingerprints. This polymer can then be detected and a fingerprint visualised. Paul Kelly and colleagues discovered that the polymerisation still occurs when the chemicals that were thought to trigger the polymerisation are washed off, either by wiping a surface or by an explosive blast. The polymerisation is triggered by a surface effect, brought about by interaction of the chemicals in the fingerprint, before they are removed.

As long as the print has existed long enough to bring this about before washing off, the signature will be present and imaging is possible. The key to this process is that it is “based on the interaction of S2N2 vapour with the surface”. The crucial point is that a vapour can reach areas of a surface that are not accessible to solids and liquids, such as the crumpled remains of an explosive device.

The authors say further research is needed to develop the method to the stage where it could be used, forensically. Work is ongoing to develop the method for use on real life samples.

Original publication: S. M. Bleay, P. F. Kelly and R. S. P. King, J. Mater. Chem., 2010

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