Hg(II) immobilization and detection using gel formation with tetra-(4-pyridylphenyl)ethylene and an aggregation-induced luminescence effect

Abstract

Tetra-(4-pyridylphenyl)ethylene (TPPE), featuring an aggregation-induced luminescence effect (AIE), has been synthesized and used for selective detection of Hg2+ in DMF/H2O (3:7, v/v) binary solutions. There was a color change from colorless to yellow in the detection of the Hg2+ ions, in addition to an increased fluorescence emission. This shows that TPPE will function as an excellent “turn-on” fluorescence probe in the detection Hg2+. Moreover, the interference of Al3+, Ba2+, Mn2+, Ca2+, Fe3+, Cu2+, Ag+, Cd2+, Co2+, Ni2+, Mg2+, Pb2+, Zn2+, and Cr3+ ions was found to be negligible under optimized solvent conditions. Cysteine and EDTA were also found to form TPPE-based fluorescent switches with the Hg2+ ions. The practical use of the TPPE sensor was also demonstrated by using a specific test kit. Characterization using FT-IR, NMR titration, UV titration, EDS, and HR-MS techniques showed that Hg2+ will form a 1:1 complex with TPPE. Also, the observation of a Tyndall effect, in addition to UV absorption and fluorescence spectra, did clearly demonstrate the presence of an AIE. More noteworthy, TPPE and Hg2+ were found to form a metal–organic gel (MOG) in the DMF solution. The SEM, TEM, ICP, and Zeta potential analyses confirmed that the fluorescent MOG could further adsorb an excess of Hg2+ ions. The BET analyses revealed that the MOG showed a type IV-H3 hysteresis loop according to the International Union of Pure and Applied Chemistry classification. The results of the XRD analysis and of the spectroscopic titrations show that a π–π stacking may be the auxiliary driving force for the gel formation, after that a coordination has taken place. These results indicate that further research on structurally simple metal ion fluorescent probes, which are based on the AIE, is promising for the achievement of a simultaneous fluorescent detection and adsorption of heavy metal pollutants.

Alkynylated and triazole-linked aroyl-S,N-ketene acetals: one-pot synthesis of solid-state emissive dyes with aggregation-induced enhanced emission characteristics

“…In 2020, the IUPAC recognized its relevance by naming AIE one of the “Top Ten Emerging Technologies in Chemistry” 8 , thus recognizing the myriad of possibilities to apply AIEgens 9 , 10 . There are basically no boundaries for AIE chromophores getting used in countless fields of academia and industry, from obvious ones like OLEDs 11 or photovoltaics 12 to sensing technologies for biological 13 and medicinal applications 14 , 15 , in bioimaging 16 , metal ion detection 17 up to comparably surprising ones like radiation identification 18 , fingerprint analysis 19 or as smart materials 20 , 21 .…”