Long-wavelength emission carbon dots as self-ratiometric fluorescent nanoprobe for sensitive determination of Zn 2 .

A novel ratiometric fluorescence nanoprobe based on long-wavelength emission carbon dots (CDs) was designed for high sensitive and selective detection of Zn 2+ . The CDs were conveniently prepared by a one-step solvothermal treatment of formamide and glutathione (GSH). Under single excitation wavelength (420 nm), the obtained CDs exhibit three emission peaks at 470, 650, and 685 nm, respectively. For the long-wavelength emission region of the CDs, the fluorescence at 685 nm can be quenched with different levels upon the addition of most metal ions. However, the presence of Zn 2+ not only results in the fluorescence quenching at 685 nm effectively but also enhances at 650 nm remarkably, which may be due to the formation of CD-Zn 2+ chelate complex inducing the dispersion of CDs aggregates and changes in the group distribution on the surface of CDs. Taking the advantage of the unique fluorescence response induced by Zn 2+ , the prepared CDs were successfully employed as nanoprobe for self-ratiometric fluorescence determination of Zn 2+ with F 650 /F 685 as signal output. A good linear relationship in the concentration range 0.01 to 2 μM, and a detection limit as low as 5.1 nM has been obtained. The ratiometric nanoprobe was successfully applied to  Zn 2+ determination  in human serum samples.