Ionic Liquid‐Functionalized CQDs as Effective “Signal‐Off” Fluorescence Nanoprobes for Selective and Sensitive Detection of Iron (III) and Chromium (VI)

Abstract Ionic liquid‐functionalized carbon quantum dots (ILCQDs) were directly synthesized by one‐pot pyrolysis from citric acid and 1‐aminopropyl‐3‐methyl imidazole bromide. ILCQDs emitting blue fluorescence and exhibiting photoluminescence quantum yield of 5.69 % were characterized by TEM, SAED, SEM, EDS, XRD, FTIR, XPS, UV‐vis, fluorescence, zeta potential, TGA and 1 HNMR. They were nanoparticles with high surface positive charges. Meanwhile, ILCQDs exhibited excitation‐dependence, stability and superior water dispersibility. Due to static quenching and internal filtering effects, their fluorescence was effectively quenched by Fe 3+ and Cr VI . Consequently, they were exactly developed as effective “signal‐off” fluorescent nanoprobes for selective and sensitive detection of Fe 3+ and Cr VI . ILCQDs‐based fluorescent nanoprobes had wider linear ranges and the limits of detection for Fe 3+ cation and Cr VI anion reached as low as 11.38 μM and 4.04 μM, respectively. More importantly, ILCQDs were successfully applied to detection of Cr VI in practical water samples and recoveries were 91.59 %–101.28 %, suggesting ILCQDs had promising application in environmental analysis.