Optical Microscopy and Atomic Force Microscopy Imaging of 2,4,6-Trinitrotoluene Droplets and Clusters on Mica

Optical and atomic force microscopy (AFM) were used to image 2,4,6-trinitrotoluene (TNT) on a cleaved mica (001) surface. The vapor deposition of TNT resulted in ellipsoidal drop formation on the mica surface. The growth rate of the drop diameter was found to be linear with vapor dosing time while the drop density followed a 1/r2 dependence, where r is the length of the major axis of the ellipsoid, for increasing dosing times. TNT platelets surrounded by a region depleted of drops were observed after 8 hours of dosing. The depleted region is attributed to a 10% shrinkage for liquid-solid transition for TNT and also from the enthalpy of fusion which causes the vaporization of small drops and clusters of TNT. Residues of TNT located in the depleted regions were characterized by AFM lift-off forces and were attributed to different morphologies of TNT that nucleated at different sites on the mica surface or dinitro- and trinitro-benzene derivatives which are common impurities in 2,4,6-trinitrotoluene.