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Sensitivity gains in chemosensing by lasing action in organic polymers


Societal needs for greater security require dramatic improvements in the sensitivity of chemical and biological sensors. To meet this challenge, increasing emphasis in analytical science has been directed towards materials and devices having highly nonlinear characteristics; semiconducting organic polymers (SOPs), with their facile excited state (exciton) transport, are prime examples of amplifying materials1,2,3. SOPs have also been recognized as promising lasing materials4, although the susceptibility of these materials to optical damage has thus far limited applications. Here we report that attenuated lasing in optically pumped SOP thin films displays a sensitivity to vapours of explosives more than 30 times higher than is observed from spontaneous emission. Critical to this achievement was the development of a transducing polymer with high thin-film quantum yield, a high optical damage threshold in ambient atmosphere and a record low lasing threshold. Trace vapours of the explosives 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) introduce non-radiative deactivation pathways5 that compete with stimulated emission. We demonstrate that the induced cessation of the lasing action, and associated sensitivity enhancement, is most pronounced when films are pumped at intensities near their lasing threshold. The combined gains from amplifying materials and lasing promise to deliver sensors that can detect explosives with unparalleled sensitivity.

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Figure 1: Test structures and materials used to demonstrate lasing chemosensory responses.
Figure 2: Stimulated and spontaneous emission of polymer 1 atop a polydimethylsiloxane DFB structure, which is shown in Fig. 1b.
Figure 3: Performance of an optically pumped thin film of polymer 1 on parylene-coated glass before and after exposure to DNT.
Figure 4: Response of a ring-mode laser coated with polymer 1.


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This work was supported by NASA, the Institute for Soldier Nanotechnologies, and the NSF through the Center for Materials Science and Engineering. A.R. acknowledges V. Sundar and H. Eisler for discussions and J. Ho for providing the DFB structures used in this work.

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Correspondence to Timothy M. Swager or Vladimir Bulović.

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Supplementary information

Supplementary Notes

This file contains the Supplementary Methods, Supplementary Data (including Supplementary Figures S1-S4) and additional references. The file details the synthesis of Polymer 1 (part A), theoretical model of TNT quenching of lasing action (part B), data on photostabiltiy of Polymer 1 laser devices (part C) and high-resolution spectra of multimode lasing of Polymer 1 in asymmetric waveguides (part D). (PDF 160 kb)

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Rose, A., Zhu, Z., Madigan, C. et al. Sensitivity gains in chemosensing by lasing action in organic polymers. Nature 434, 876–879 (2005).

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