Mar 28, 2008
Multiphoton excited macromolecules as explosive sensors
With a combination of exceptional spectroscopic tools and nonlinear optical organic nanomaterials it is now possible to detect energetic materials with a high level of sensitivity at long remote distances. These new findings open up new avenues in fundamental research as well as in the design of electronic and optical devices. Strong interchromopore interactions with specifically designed topologies of organic macromolecules allow for the enhanced sensitivity of these new sensory materials.
The technology was developed at the University of Michigan by Professor Theodore Goodson III and his co-workers Dr Oleg Varnavski and Aditya Narayanan. This novel technology in fluorescence chemical sensing utilizes two-photon excited fluorescence with laser light in the infrared spectral region. This technology can be used for excitation of remote sensors of energetic materials, such as TNT. The use of infrared light is beneficial particularly for vapor sensing and has a greater penetration depth through the atmosphere. There is also less concern regarding eye safety in remote detection schemes.
Goodson’s group has investigated new dendritic materials as promising two-photon sensors for TNT detection. The dendrimer molecules were synthesized in collaboration with Professor Mireille Blanchard-Desce (Université de Rennes 1, France) and Professor Jean-Pierre Majoral (Laboratoire de Chimie de Coordination, CNRS, Toulouse, France). It was found that these materials possess large two-photon absorption cross-sections and show superior amplified fluorescence quenching by TNT. The potential applications of this effect are exciting and encompass many areas of science and technology.
Using femtosecond spectroscopy Goodson’s lab has also demonstrated the mechanism of the efficient amplified quenching, which is connected to the exciton migration over the spherical surface of the dendrimer molecule.
About the author
Theodore Goodson III is a professor of chemistry at the Department of Chemistry, Applied Physics and Macromolecular Science and Engineering, University of Michigan Ann Arbor, MI, US. He is currently conducting research projects on new nonlinear optical macromolecular materials, structure-function relationships in macromolecular materials, ultrafast spectroscopy, and quantum optical effects using new organic materials.