New imine-linked conjugated mesoporous polymer for the turn-on fluorescence detection of Ga3+

Abstract

The synthesis of conjugated mesoporous polymers at room temperature has always been challenging. Herein, for the first time, we have been successfully synthesized a conjugated mesoporous fluorescence polymer named TM–HB through the Schiff-base condensation of tris(4-aminophenyl)methane (TM) and 5-hydroxy-benzene-1,3-dicarbaldehyde (HB) at room temperature. FT-IR, XPS and ¹³C CP/MAS NMR analysis in the solid state confirmed imine formation, and PXRD analysis proved its amorphous structure. It was found that TM–HB had mesopores with elevated thermal resistivity. TM–HB can qualitatively and quantitatively detect Ga³⁺ ions in acetonitrile via “turn-on” fluorescence change with high selectivity and sensitivity, accompanied with a significant fluorescence color change. Furthermore, selective changes in UV-vis absorbance spectra and solution color further confirmed that TM–HB can selectively interact with Ga³⁺ ions over other metal ions. The fluorescence intensity of TM–HB at 335 nm showed a linearity up to 320 μM with the lowest limit of detection (LOD) of 0.46 μM and a high correlation coefficient (R² = 0.99122). The practicability of TM–HB in real life applications was proven by its good recovery in different water samples. DFT calculations helped elucidate complex formation while synergistic chelation-enhanced fluorescence (CHEF) and photoinduced electron transfer (PET) explained the complexation mechanism. The synthesis of TM–HB at room temperature opens new pathways for temperature-sensitive organic moieties and may encourage researchers all over the world to recognize its potential applicability in protecting and safeguarding humanity and the environment.