Pyridine and Cyclohexylamine Fluorescence Paper Sensors Based on Two cubane-type Cu4I4 Clusters

Abstract

A cubane-type Cu₄I₄ cluster 3-PhPy₄Cu₄I₄ (1) was designed and synthesized (3-PhPy = 3-phenylpyridine). The cluster was characterized by elemental analysis, X-ray diffraction, FTIR and UV-Vis spectroscopic analysis. Single-crystal X-ray diffraction revealed that cluster 1 presents a supramolecular interlocking chain structure. Similar cluster 4-PhPy₄Cu₄I₄ (2) was also prepared and re-determined. The TD-DFT calculations reveal that their UV-Vis absorption and luminescence originate from the hybrid [(X + M)LCT] excited states. Based on the cluster 1, a paper-based sensor (1) was prepared through a composite process, it shows a remarkable PL quenching response for pyridine (Py) / cyclohexylamine (CYA) detection with good selectivity. Using this sensor, an amazing sensing speed of T₉₀ = 5 s was achieved for the detection of Py and T₉₀ = 10 s for CYA. In the fluorescence sensing response of these two volatile organic compounds, their maximum fluorescence quenching efficiency reached outstanding 98%. The sensor (2) based on cluster 2 also demonstrated similar fluorescence sensing performance for selective detection of Py or CYA.