A simple and robust PET-based anthracene-appended O-<i>N</i>-O chelate for sequential recognition of Fe³⁺/CN^&#x2013; ions in aqueous media and its multimodal applications

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>A very simple, robust, and pico/nanomolar-sensitive 9,10-diethanolamine-substituted fluorescent Fe<SUP>3+</SUP>/CN<SUP>–</SUP> probe (<B>PD</B>) was synthesised, and its sensing abilities towards various ions were studied in mixed aqueous media. <B>PD</B> selectively recognised Fe<SUP>3+</SUP> ions through a ‘<I>turn on</I>’ response with an excellent binding constant (<I>K</I> <SUB>a</SUB>, 9.29 × 10<SUP>6</SUP> M<SUP>−1</SUP>) in 1:2 binding stoichiometry at pH 7.0 in phosphate-buffered saline (PBS). The <I>in situ</I> generated Fe<SUP>3+</SUP>·<B>PD</B> ensemble sequentially recognised CN<SUP>–</SUP> ions with an excellent binding constant (<I>K</I> <SUB>a</SUB> 1.72 × 10<SUP>8</SUP> M<SUP>−1</SUP>) via a ‘<I>turn off</I>’ mode by extruding Fe<SUP>3+</SUP> ions from the ensemble. The highly selective sequential ‘<I>on-off</I>’ responses towards Fe<SUP>3+</SUP> and CN<SUP>–</SUP> ions were attributed to inhibition and restoration of photoinduced electron transfer (PET) and chelation-induced enhanced fluorescence (CHEF) effects from the chelating N and O heteroatoms. <B>PD</B> was able to detect Fe<SUP>3+</SUP> and CN<SUP>–</SUP> ions in real water samples satisfactorily at picomolar to sub-nanomolar levels. A colorimetric assay based on pyrocatechol violet (<B>PCV</B>) was also able to detect Fe<SUP>3+</SUP>/CN<SUP>–</SUP> in a sequential manner (up to sub-micromolar level) by a change in colour from colourless to yellow/pale green without any interferences from other ions. Based on the complexation and decomplexation mechanism, bio-imaging photonic INHIBIT logic circuit strips were prepared for use under physiological conditions. In addition, solid-phase recognition of Fe<SUP>3+</SUP>/CN<SUP>–</SUP> ions was demonstrated using cost-effective paper-based strips.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 9,10-Diethanolamine-appended anthracene probe PD was synthesized and sensing abilities were studied in aqueous medium. </LI> <LI> Probe PD detected Fe<SUP>3+</SUP> and CN<SUP>–</SUP> sequentially through ‘<I>switch-on</I>’ and ‘<I>switch-off</I>’ responses. </LI> <LI> Pyrocatechol violet based colorimetric assay also is able to detect Fe<SUP>3+</SUP>/CN<SUP>–</SUP> in sequential manner by changing the color from colorless to yellow/pale green. </LI> <LI> Bio-imaging, photonic INHIBIT logic circuit strips were demonstrated at physiological conditions based on complexations and decomplexation mechanism. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>