Colorimetric and fluorimetric (dual-mode) nanoprobe for the determination of pyrogallol based on the complexation with copper(II)- and nitrogen-doped carbon dots.

Carbon dots doped with copper(II) and nitrogen (Cu,N@C-dots) were prepared and are shown to be viable fluorescent nanoprobe for pyrogallol (PGL) was developed for the first time. The reaction is based on (a) the complexation reaction between Cu,N@C-dots and catechol moiety, and (b) the generation of a quinone-like structure. Thus, the co-ordination complex formed between Cu(II) in C-dots and PGL results in quenching of the fluorescence of C-dots. In addition, the formation of a yellow color due to complex formation between the nanoprobe and Cu(II) allowed the colorimetric determination of PGL. The nanoprobe was prepared by thermal synthesis, using ethylenediaminetetraacetic acid salt and copper(II) chloride as sources for carbon, nitrogen and copper, respectively. The carbon dots were characterized by UV-VIS spectroscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, transmission electron microscopy) and dynamic light scattering. Fluorescence drops linearly in the 0.15 to 70 μM PGL concentration range with a detection limit of 39 nM and a relative standard deviation of 1.8%. The optimal excitation and emission wavelengths are 370 nm and 428 nm, respectively. The colorimetric assay has a linear response at 325 nm absorption wavelengths in the 6 to 140 μM PGL concentration range with a detection limit of 1.8 μM and a 2.3% relative standard deviation. Graphical abstractDual mode colorimetric and fluorimetric nanoprobe was designated for pyrolgallol determination based on complexation with copper(II)- and nitrogen-doped carbon dots.