Nitrogen and sulfur co-doped carbon dot-based ratiometric fluorescent probe for Zn²⁺ sensing and imaging in living...

A near-infrared nitrogen and sulfur co-doped carbon dot (N,S-CD)-based ratiometric fluorescent probe is proposed that is synthesized via hydrothermal approach using glutathione and formamide as precursor for sensing and imaging of Zn²⁺. The prepared N,S-CDs facilitate binding with Zn²⁺ owing to N and S atom doping. The ratio (I₆₅₀/I₆₈₀) of fluorescence intensity at 650 nm and 680 nm increased with the concentrations of Zn²⁺ when the excitation wavelength was 415 nm. The linearity range was 0.01 to 1.0 μM Zn²⁺with a detection limit of 5.0 nM Zn²⁺. The proposed probe was applied to label-free monitoring of Zn²⁺ in real samples and fluorescent imaging of Zn²⁺ in living cells, which confirmed its promising applications.