Fluorescent films that can sense explosives have been developed by Chinese scientists.

Guangtao Li from Tsinghua University, Beijing, and colleagues have made silica films doped with nitrogen-containing macrocyclic molecules, porphyrins. Even trace levels of explosives such as TNT can cause a fluorescent response in the films.

Current fluorescent sensors for TNT are based upon conducting polymers, which can be hard to make and unstable. According to Li, the films he has developed can overcome these problems. 'In comparison to other fluorescence-based sensory materials these films offers a simple preparation procedure from inexpensive materials, as well as stabilisation of the sensing elements in an inorganic matrix,' he explained. He believes that the high sensitivity of the films to vapour from explosives is due to their porous structure and large surface area.

Timothy Swager, a pioneer in this field from the Massachusetts Institute of Technology, US, is excited by this work. 'The results demonstrate the power of a mesostructured support to obtain high sensitivity by more effectively capturing and binding nitroaromatic explosives. The team have surpassed the sensitivities reported for early generation amplifying fluorescent polymers and demonstrated a general approach to achieve ever lower detection limits,' he said.

Li and his team aim to achieve even lower detection limits. 'Our goal is the fabrication of chemosensory materials that could have detection performance comparable to that of the historical gold standard - dogs. By using porous materials we hope that high-performance commercial chemosensory devices for explosives detection will be developed,' he said.

Rebecca Gillan