Large Stokes shift red-emissive CDs-based ternary complexes for ratiometric/visual detection of triethylamine

As triethylamine (TEA) is a critical indicators for evaluating seafood freshness to ensure edible safety and human health, developing a strategy for rapid, sensitive and on-site monitoring TEA possesses an important research significance.

The novel strategy of constructing ratiometric fluorescent platform for TEA detection is proposed based on ternary nanocomposites. Red-emissive carbon dots (R-CDs) with large Stokes shift were firstly synthesized by using citric acid and neutral red as dual carbon sources while UiO-66-NH₂ were prepared by 2-aminoterephthalic acid and zirconium tetrachloride via solvothermal approach. After that, R-CDs and riboflavin (RF) self-assembled on the surface of UiO-66-NH₂ to form ternary nanocomposites (R-CDs@UiO-66-NH₂@RF), displaying dual-response modes: ratiometric and visual detection of TEA. Under single-excitation at 370 nm, ternary nanocomposites exhibit two emission peaks at 426 and 530 nm which ascribes to R-CDs and RF, respectively. Third, UiO-66-NH₂ with large surface area brings R-CDs close proximity to RF, resulting in occurrence of FRET from RF to R-CDs. More interestingly, after the introduction of TEA, the emission intensity at 530 nm appears significant decrease due to photo-induced electron transfer while that at 426 nm nearly keeps the constant. Based on these phenomena, a ratiometric approach for detecting TEA has been proposed with the detection limit of 0.28 nM. Furthermore, intelligent visual sensing approach was also fabricated by combining test strips with smartphone-assisted RGB analysis, achieving on-site monitoring of TEA gas and real-time assessment of seafood freshness.

Our present ratiometric/intelligent sensing platform offers a convenient and alternative approach for food safety control.