An explosive innovation

researchers have developed a new polymer that greatly increases the sensitivity of chemical detection systems for explosives such as TNT (trinitrotoluene).

In the April 14 issue of Nature, they described a polymer that undergoes lasing action at lower operating powers than previously observed, and they demonstrated that the stimulated light emission from the lasing modes of the polymer displays inherently greater sensitivity to explosives vapours.

Professor Tim Swager and Professor Vladimir Bulovic led the team that designed the novel semiconducting organic polymer (SOP) and invented the new chemosensing method.

When exposed to ultraviolet light above a threshold intensity, the material undergoes a stimulated emission or a lasing process, manifested by a directed beam of light emanating from the thin SOP film. When TNT is present, it binds to the SOP surface and quenches the beam.

Because the new polymer undergoes stimulated emission at lower thresholds than earlier SOP materials, the intensity of the ultraviolet light needed to start the lasing action (pump power) is reduced by more than tenfold. This lowers the optical damage usually caused to organic molecules under intense illumination in air. By adjusting the pump power to just over the threshold needed for lasing, it is possible to dramatically attenuate the lasing emission with parts-per-billion doses of TNT vapour. The result is a thirtyfold increase in the detection sensitivity when the system is operating near the lasing threshold.