Meisenheimer complex between 2,4,6-trinitrotoluene and 3-aminopropyltriethoxysilane and its use for a paper-based sensor

2,4,6-Trinitrotoluene (TNT) forms a red-colored Meisenheimer complex with 3-aminopropyltrienthoxysilane (APTES) both in solution and on solid phase. The TNT–APTES complex is unique since it forms yellow-colored complexes with 2,4,6-trinitrophenol and 4-nitrophenol, and no complex with 2,4-dinitrotoluene. The absorption spectrum of TNT–APTES has two absorption bands at 530 and 650 nm, while APTES complexes with 2,4,6-trinitrophenol and 4-nitrophenol have absorption maxima at around 420 nm, and no absorption change for 2,4-dinitrotoluene. The TNT–APTES complex facilitates the exchange of the TNT-CH3 proton/deuteron with solvent molecules. The red color of TNT–APTES is immediately visible at 1 μM of TNT.