Ln-incorporated coordination complexes as fluorescence sensor for selective detection nitroaromatic compounds

Highlights: • A novel coordination complex was used as precursor material to obtain Ln-incorporated luminescent materials. • Ln@1 materials displayed excellent properties in detection of nitroaromatic compounds by fluorescence quenching method. • Ln@1 materials as portable sensing agents to make the fluorescent papers strip for visual detection of NACs. -- Abstract: A new Zn(II)-based coordination complex, [Zn(L)₂]·(CH₃OH)_0.5·(H₂O)₂ (1) (L = 3-chloro-6-(3-methyl-5-phenyl-1H-pyrazol-1-yl) picolinic acid) has been synthesized by solvothermal condition. The uncoordinated oxygen atoms in the compound can be used as active sites for post-synthetic modifications. Therefore, compound 1 can act as a precursor material for coating lanthanides. The Ln@1 (Tb@1 and Eu@1) materials showed characteristic emission properties of Ln³⁺ ions. These emissions are selectively quenched by nitroaromatic compounds in ethanol with good sensitivity. The result illustrated that the materials selectively detect of 2,4,6-trinitrophenol (TNP), 2,4-dinitroaniline (2,4-NA) with higher efficiency (Ksv>10⁴ M⁻¹) compared with other nitroaromatic compounds, including 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), nitrobenzene (NB), 4-nitrophenol (4-NP), 4-nitrotoluene (4-NT). Furthermore, the fluorescent paper strips were prepared in order to make them as portable sensing agents. In addition, a probable sensing mechanism was also discussed in this paper.