화학공학소재연구정보센터
Applied Surface Science, Vol.455, 533-542, 2018
Molecular dynamics simulation of gaseous nitroaromatic compounds interacting with silica surfaces under various humidity conditions
The microscopic behavior of vapors of nitroaromatic compounds (NAC) interacting with the surface of sensitive materials is studied using molecular dynamic simulations, in view of contributing to the development of sensors capable of detecting trace amounts of these explosives in the atmosphere. More specifically, we consider two NAC target, namely trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT), along with three kinds of silica surfaces: standard silica with hydroxyl groups at its surface (Silica-OH), ethoxylated (Silica- OEt/OH) and methylated (Silica- Me-2/OH) silica. The latter surface is of practical interest for sensing applications. These systems are simulated under various humidity conditions, ranging from a dry to a rainy weather environment. The simulations are carried out at high temperature and extrapolated to ambient temperature according to a previously established procedure. The results show that both water and NAC adsorb rapidly onto silica surfaces by avoiding the carbons of the ethoxy or methyl groups. Under dry conditions, TNT, and to a lesser extent 2,4-DNT, lie parallel to the silica surface. Interestingly, despite their close structural similarity, these two molecules exhibit strikingly different responses to humidity regarding their orientation with respect to the Silica- Me-2/OH surface. Indeed, on going from dry to wet conditions, the alignment of TNT becomes more random, whereas the parallelism of 2,4-DNT molecules becomes more pronounced.