High-sensitivity detection of nitroaromatic compounds (NACs) by the pillared-layer metal-organic framework synthesized via ultrasonic method.

Nanorods of zinc(II) based metal-organic framework (MOF) were prepared via ultrasonic method without any surfactants at room temperature and atmospheric pressure. Control of particle size and morphology was enhanced in this synthesis method. Nanorods of pillared-layer metal organic framework, [Zn2(ubl)2(bipy)]·DMF (TMU-18), where ubl (urea-based ligand) is 4,4'-carbonylbis(azanediyl)dibenzoic acid, 4,4'-Bipyridine (bipy) DMF = N,N-dimethyl formamide), was synthesized under ultrasound irradiation in different concentrations of initial precursor. The nano structure and morphology of the synthesized MOF were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), powder X-ray diffraction, elemental analysis and FT-IR spectroscopy. Moreover, Fluorescence emissions of nanorods have been studied. Luminescent MOFs (LMOFs) have shown great potential as sensor for various nitro explosives by modulating the luminescence behavior in presence of nitro explosives. Urea-functionalized MOF shows high selectivity for sensing of the nitro explosive 2,4,6-trinitrophenol (TNP) even in the presence of other nitroaromatic compounds in methanol solution. Fluorescence intensity decreased with increasing contents of nitroaromatics in organic solution due to fluorescence quenching effect. The ultrasound method has some advantages such as short duration time of reaction, no need to high temperatures and pressures for synthesis nano-materials and low costs in comparison to other methods. Considering these advantages we used ultrasonic method to produce these nanorods which show high sensitivity in detecting nitroaromatics.