Abstract
By using Schiff base tricarboxylate ligand 5-(4-carboxybenzylideneamino)isophthalic acid (H3CIP), a new imine functionalized copper metal organic framework (MOF) has been synthesized solvothermally. It was fully characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and elemental mapping techniques. The as-synthesized MOF has been utilized as fluorescent probe for detection of nitro aromatic explosives (NAEs). The results show that the copper MOF can be developed into highly selective and sensitive sensor for detection of TNP in the aqueous medium via the "turn-off" quenching response. The linear fitting of the Stern-Volmer plot for TNP offered large quenching constant of 1.07 × 104 M-1 for Cu-MOF indicating the high sensitivity of the sensing process. Outstanding sensitivity of prepared material towards TNP detection was further validated by the low detection limit of 80 ppb (0.35 µM). The detailed mechanistic studies for their mode of action and density functional theory (DFT) calculations reveals that photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) processes, as well as electrostatic interactions (i.e. H-bonding) are the key factors for the turn-off response toward TNP by this fluorescent sensor. Thus, this new LMOF owing to their high water stability and remarkable functional features are potential candidates which can be developed into selective and sensitive TNP detection devices.
Highlights
Development of highly selective and sensitive sensing materials for the detection of hazardous nitro explosives (NEs) has become one of the most critical concerns all over the world because of ever increasing terrorist activities and unpredicted industrial disasters [1]
Diverse analytical techniques e.g. mass spectrometry [6], high performance liquid chromatography (HPLC) [7], ion-mobility spectroscopy (IMS) [8], electrochemical methods [9], and fluorescence spectroscopy [10] have been employed for the detection of TNP
The strong peak at 1725 cm−1 which corresponding to the characteristic antisymmetric stretch absorption of carbonyl of –COOH group, present in the H3CIP disappear in the copper Metal-organic framework (MOF) (Figure 1b)
Summary
Development of highly selective and sensitive sensing materials for the detection of hazardous nitro explosives (NEs) has become one of the most critical concerns all over the world because of ever increasing terrorist activities and unpredicted industrial disasters [1] Both aromatic and aliphatic nitro compounds such as 2,4,6-trinitrotoluene (TNT), nitrobenzene (NB), 2,6-dinitrotoluene (2,6-DNT), 3,4-dinitrotoluene (3,4-DNT), 1,3dinitrobenzene (1,3-DNB), 2,4,6-trinitrophenol (TNP; known as picric acid, PA), and nitro methane etc. Diverse analytical techniques e.g. mass spectrometry [6], high performance liquid chromatography (HPLC) [7], ion-mobility spectroscopy (IMS) [8], electrochemical methods [9], and fluorescence spectroscopy [10] have been employed for the detection of TNP Among these fluorescence spectroscopy have gained tremendous attraction of the researchers because of its easy operation, low cost, good sensitivity/selectivity, and quick response time, etc. Among these fluorescence spectroscopy have gained tremendous attraction of the researchers because of its easy operation, low cost, good sensitivity/selectivity, and quick response time, etc. [11]
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