A new strategy to design colorful ratiometric probes and its application to fluorescent detection of Hg(II)

Abstract

A new strategy has been proposed to expand color-tunability of ratiometric fluorescent probes. It was shown that the combination of blue emissive color (as an internal standard) and yellow emissive color (as a probe) is an efficient way to create an extensive color range in ratiometric probes. However, due to the nature of the interaction between the analyte and the probe in terms of fluorescence quenching, occurance of the redshift in the emission is the major provision of such a probe. Our developed ratiometric fluorescence probe consists of blue emissive carbon dots (BCDs) and thioglycolic acid (TGA)-capped yellow emissive cadmium telluride (CdTe) quantum dots (YQDs). The ratiometric probe exhibits dual-emissions which are centered at 443 and 560 nm under a single excitation wavelength of 360 nm. With the exposure of Hg(II) ions (as an example) to the probe, the fluorescence of YQDs is selectively quenched and redshifted. The emission of probe displays continuous color changes from strong green into light green, yellow-green, yellow, orange, pink, purple, weak blue, and dark blue. The fluorescent ratiometric probe demonstrates a broad dynamic linear range from 10 nmol L−1 to 1.4 μmol L−1 with a detection limit as low as 4.6 nmol L−1. In addition, the wide-color-varying probe shows an excellent capacity to determine Hg(II) ions in environmental samples.