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

Abstract

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 H2O2-o-phenylenediamine (OPD) reaction. At the same time, the OPDox had an excellent fluorescence (FL) property. Under the excitation wavelength at 390nm, a novel FL emission ascribed to OPDox was clearly observed at 565nm. In addition, the FL at 565nm gradually increased, while the FL of emission peak at 450nm 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 0.09–50μM and the limit of detection was 0.06μM. 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.