Carbon nanodots calibrated fluorescent probe of QD@amphiphilic polyurethane for ratiometric detection of Hg (II)

Because of its strong toxicity to the ecosystem and human beings, mercury is regarded as one of the most hazardous heavy metals. Among various fluorescent sensors that have been designed for Hg (II) detection, the probes showing Hg (II) concentration dependent ratiometric fluorescent responses normally exhibited improved analytical performance. Herein, we have synthesized series of amphiphilic polyurethane (PU) to encapsulate hydrophobic fluorescent quantum dots (QD) via the emulsion confinement self-assembly, leading to generation of QD@PU colloids whose red emission can be selectively quenched by Hg (II) among other metal ions. In order to further improve the Hg (II) detection performance of QD@PU probe, the green emitting carbon nanodots (CD) were synthesized and conjugated with QD@PU, resulting to formation of CD-QD@PU colloidal probe showing ratiometric fluorescent response towards Hg (II), which finally contributed to an enhanced sensitivity and wider linear range for Hg (II) detection. More interestingly, both QD@PU and CD-QD@PU doped stretchable PU membranes still hold naked eye discrimination for Hg (II). Basically, the current work revealed a universal protocol to prepare fluorescent probe for Hg (II) detection using PU and low dimensional fluorescent nanoparticles as building blocks, which will open new way for design and fabrication of other advanced sensors and analytical devices.