Gomez De Arco, Lewis M.

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UV femtosecond laser photochemistry of TNT: A near field scanning optical microscopy study
(2004) Gomez De Arco, Lewis M.; Castro, Miguel; College of Arts and Sciencies - Sciences; Briano, Julio; Hernandez, Samuel; Department of Chemistry; Colucci, Jose
Laser-based sensor development has become a field of interest due to environmental and security reasons. In this work, an ultrafast femtosecond pulsed laser was coupled to an AFM/NSOM system to study the photochemistry of particles and solutions of TNT under environmental conditions. Vibrational spectroscopy analysis performed on the dry deposits of irradiated TNT solutions reveals that photolysis products of TNT solutions depend on the solvent nature. Nanosized TNT particles were deposited on a transmissive substrate and characterized by atomic force and electron microscopy. The chemical composition of the particles was confirmed by surface reflection FTIR and energy dispersive X-ray spectroscopy analysis. TNT single particles showed fluorescence signal upon illumination with 266 nm pulses within the near field. The fluorescence signal is attributed to photo-dissociated NO due to TNT fragmentation, and the fluorescence yield resulted to be characteristic of a multi-photon absorption process. These results represent a significant advance in the chemical trace detection of warfare agents in open environments.