Efficient smart-phone luminescent sensing detection based on new multifunctional Cd(II) luminescent coordination polymers

Based on the mixed ligand strategy, two new isostructural Cd^II coordination polymers: {[Cd₃(tcpa)₂(bima)(DMF)]‧3DMF} (CP 1), {[Cd₃(tcpa)₂(bmima)(DMF)]‧3DMF} (CP 2) were synthesized by combining two flexible anthracene-based and a triphenylamine-based ligands with large π-electron-rich structure using a solvothermal method (H₃tcpa = tris(4-carboxyphenyl)amine; bima = 9,10-bis(1H-imidazole-1-yl)methyl)anthracene and bmima = 9,10-bis((2-methyl-1H-imidazol-1-yl)methyl)anthracene). CP 1 and CP 2 show an unreported new 3D (3,14)-c net structure with the {4³⁰·6⁴⁸·8¹³}{4³}₄ topology. Both CPs could detect Cr₂O₇²⁻, Nitroaromatic explosives 2,4,6-Trinitrophenol (TNP) and 2,4-dinitrophenol (DNP) through rapid fluorescence quenching response with high quenching efficiency Ksv and low LOD with 0.19 μM (Cr₂O₇²⁻), 0.54 μM (TNP), 0.76 μM (DNP) for CP 1 and 0.28 μM (Cr₂O₇²⁻), 0.23 μM (TNP), 0.65 μM (DNP) for CP 2, respectively. In addition, the mechanism of quenching Cr₂O₇²⁻, TNP and DNP by CPs is proposed through experimental research and theoretical simulation. The quenching of Cr₂O₇²⁻ by CPs is mainly competitive absorption (CA), while the quenching of TNP/DNP is achieved through the coexistence of competitive absorption CA, photo induced electron transfer (PET) and fluorescence resonance energy transfer (FRET). Moreover, we have been developed a portable smartphone-assisted on-site detection platform, which can perform semi-quantitative analysis of Cr₂O₇²⁻ acconding to fluorescence color changes. This work constructed a ratiometric sensing platform for quickly and conveniently detection of Cr₂O₇²⁻, TNP and DNP pollutants.