A dual-signal readout sensor for highly sensitive detection of iodide ions in urine based on catalase-like reaction of iodide ions and N-doped C-dots

In this work, a novel colorimetric and ratiometric fluorescence detection method for iodide ions (I-) was developed. In the presence of I-, the color of N-doped C-dots/H2O2/OPD system aqueous solution varied from colorless to yellow due to 2,3-diaminophenazine (OPDox) produced from I--catalyzed H(2)O(2)o-phenylenediamine (OPD) reaction. At the same time, the OPDox had an excellent fluorescence (FL) property. Under the excitation wavelength at 390 nm, a novel FL emission ascribed to OPDox was clearly observed at 565 nm. In addition, the FL at 565 nm gradually increased, while the FL of emission peak at 450 nm attributed to N-doped C-dots gradually decreased with the increasing concentration of I-due to the FL resonance energy transfer (FRET) between N-doped C-dots and OPDox. Therefore, a dual-signal optical sensor was developed for detection of I-. Under the optimized conditions, the linear response to I- was in the range of 0.09-50 mu M and the limit of detection was 0.06 mu M. Moreover, this proposed assay was successfully applied for the detection of I- in urine. These results indicate that the colorimetric and ratiometric fluorescence dual-readout assay method has great potential for applications in physiological and pathological diagnosis. (C) 2017 Elsevier B.V. All rights reserved.