|M.Sc Student||Reut Shapira|
|Subject||Electrical Detection of TNT: The Interactions between|
Amines and TNT
|Department||Department of Chemistry||Supervisor||Professor Eichen Yoav|
|Full Thesis text - in Hebrew|
The rising of worldwide terror events has made the need for effective chemical detection compelling. 2,4,6-Trinitrotoluene (TNT) is one of the most common explosives. It has three carbon atoms that are susceptible to nucleophilic addition which produces a cyclohexadienyl derivative called Meisenhiemer Complex (MC). The formation of MC of TNT is associated with color formation when the colorless TNT turns deep red. Many examples of TNT-sensing are based on this selective reaction, and the sensors include nucleophilic amines to form the colored adduct. In most literature reports, the claim of MC formation relies on the observation of color change. However, color change of the solution can be caused by other phenomena as well.
Therefore, the specific reaction between TNT and n-Butylamine was studied in polar and non-polar media. The obtained products and the stoichiometry of the reaction were characterized by a variety of methods, with the development of appropriate equations where required. In acetonitrile, TNT and amine undergo an acid base displacement reaction. However, in toluene, which is a non-polar solvent, an association reaction was observed, and the product could be an aci-nitro tautomer of TNT bound with an amine molecule.
A further objective of the research described in this thesis is to identify TNT by employing its interaction with amines via a change in the electrical signal of an organic field effect transistor (OFET). Developing a semiconducting p-conjugated oligomer which includes an amine unit is expected to induce changes in its properties as a result of interaction with the analyte. Two such oligomers were synthesized by a sequence-independent method using Wittig-Horner and Heck reactions. Each oligomer was used as the conducting layer in the OFET, and one of the oligomers functioned as a hole conducting channel. Exposure of the transistor to vapors of an analog of TNT, 1,3-Dinitrobenzene, increases the source-drain current compared to the current at the inert state. This system is a breakthrough in sensitive and selective detection of explosives based on electronic devices.