A Water‐Soluble Turn‐on Fluorescent Probe for Detection and Plant Bioimaging of Al3+ and As3+ Ions

An imidazolium salt (E)‐3‐(hydroxy‐4‐(((2‐hydroxyphenyl) imino) methyl) benzyl)‐1‐methyl‐1H‐imidazol‐3‐ium chloride (HBIm) was synthesized and evaluated for its fluorescence behavior toward metal ions. The probe detected Al3+ and As3+ ions when excited at 326 nm in an aqueous medium. The non‐fluorescent HBIm exhibited a ‘turn‐on’ fluorescence response upon being treated with Al3+ (λem = 510 nm) and As3+ (λem = 499 nm) ions due to the chelation‐enhanced fluorescence (CHEF) effect. The detection limits for Al3+ and As3+ were low and found to be 0.38 nM and 2.37 nM, respectively. Furthermore, the binding constants for these ions were significantly high, 1.59 × 105 M‐1 for Al3+ and 3.54 × 104 M‐1 for As3+. The binding mechanism between HBIm and Al3+ and As3+ ions was supported by various techniques, including ESI‐MS, Job's plot, 1H NMR, XPS, SEM‐EDS and DFT studies. The reversibility experiments were conducted using EDTA ions to develop the corresponding logic gates. HBIm has the potential to detect Al3+ and As3+ ions in real samples, such as plant cells, tissues and water samples.