Application of aza-BODIPY as a Nitroaromatic Sensor

Abstract

Nitroaromatic explosive detection with high sensitivity and selectivity is requisite for civilian and military safety and the ecosystem. In this study, aza boron dipyrromethene (aza-BODIPY) dye was selected as a fluorescent-based chemosensor against nitroaromatic compounds (NACs) including 2,4,6-trinitrophenol (picric acid, TNP), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT). This dye molecule exhibits sharp fluorescent behavior with high quantum yields beyond the near-infrared region (NIR) and is considered as a potential candidate for the detection of NACs. O’Shea’s approach was used to synthesize tetraphenyl-conjugated aza-BODIPY molecules. Quenching of fluorescence emission of aza-BODIPY at 668 nm after the exposure to NACs was investigated under acetonitrile–water and acetonitrile–ethanol solvent conditions. The quenching responses and its mechanism were examined by considering the Stern–Volmer relationship Stern–Volmer constants (K sv) for TNP (in water), TNP (in ethanol), TNT, and DNT, which are predicted to be 1420, 1215, 1364, and 968 M–1, respectively, all of which are sufficiently above the limit of detection (LOD) values. Thus, the present study opens up the possibility of the usage of aza-BODIPY molecules as a low-cost, light-weight sensor for the detection of NAC explosives.

Dual-Channel Imine-Amine Photoisomerization in a Benzoimidazole and Benzothiazole Coupled System: Photophysics and Applications

“…It is observed that the emission spectrum of BIBTB is significantly changed (Figure A) in the presence of picric acid (PA) with a notable red shift of the emission band (Δλ Em ∼ 37 nm) and a concurrent reduction of emission intensity. This indicates that BIBTB functions as a highly specific sensor for the identification of PA since it only exhibits striking changes in emission peak position when PA is present. − …”

“…For investigating the mechanism of PA detection, we have presented the relative energies of the frontier molecular orbitals of both BIBTB and PA, which demonstrate a favorable energy level alignment for the electron transfer from the photoexcited BIBTB to PA. − , …”

“…As shown in Figure , the least unoccupied molecular orbital (LUMO) of BIBTB (−1.30 eV) is higher in energy compared to the LUMO of PA (−2.64 eV) and there is a possibility of photoinduced electron transfer (PET) from the LUMO of BIBTB to the LUMO of PA, resulting in quenching of the expected emission of BIBTB …”

“…Mechanism of PA Detection. For investigating the mechanism of PA detection, we have presented the relative energies of the frontier molecular orbitals of both BIBTB and PA, which demonstrate a favorable energy level alignment for the electron transfer from the photoexcited BIBTB to PA. [42][43][44][45][46]57 As shown in Figure 10, the least unoccupied molecular orbital (LUMO) of BIBTB (−1.30 eV) is higher in energy compared to the LUMO of PA (−2.64 eV) and there is a possibility of photoinduced electron transfer (PET) from the LUMO of BIBTB to the LUMO of PA, resulting in quenching of the expected emission of BIBTB. 45…”

“…Picric acid (PA) (2,4,6-trinitrophenol) is a useful reagent in organic reaction, drug detection, rocket fuel production, dye manufacturing, and potent explosive components, is a pollutant to the environment, and causes serious health issues such as skin irritation and respiratory organ damage due to its widespread use. − As a result, the sensitive method of detecting picric acid at low concentrations is always demanding . So far, fluorescence quenching and “off-on” ratiometric fluorescence sensing were reported for picric acid detection at a very low level. − Here we have shown that BIBTB behaves as a ratiometric fluorescence sensor for picric acid with a high quantum yield and a lower detection limit. We also developed an analytical application of the solvent selective behavior of BIBTB by determining the water content in a dry DMSO solvent using fluorescence quenching and shifting of band position …”