A near field optical microscopy study of trinitrotoluene

Atomic force microscopy (AFM) and near field scanning optical microscopy (NSOM) are promising analytical techniques for the determination of trace amounts of explosive materials on a variety of surfaces. Information regarding the forces of interaction and explosive spectroscopic signatures, in addition to explosive morphology, can be obtained with AFM and NSOM techniques. Basic work toward the development of methodology that can enable the employment of these techniques is needed to facilitate their employment in the field and real life scenarios. In this work, we report on the use of AFM and NSOM for the determination of the morphology and spectroscopic signature of TNT particles on optically transparent substrates open to air environments. The TNT particles are about 1 mm in diameter. Transmission NSOM on the particles following 265 nm excitation reveals that the fluorescence peak is centered at 255, about 10 cm-1 lower than the excitation wavelength. The fluorescence yield is found to increase non-linearly with incident laser power, consistent with a multi photon absorption process. The results encourage future work in the area, in particular, with the use of multi-cantilevers that can increase the surface area examined in real life scenarios.