One-step hydrothermal synthesis and optical properties of PEG-passivated nitrogen-doped carbon dots

Strongly fluorescent polyethylene glycol passivated nitrogen-doped carbon dots (P-NCDs) were prepared through a one-step facile hydrothermal process using glutamic acid as the precursor. The passivated nitrogen-doped carbon dots with an average size of 6.5 nm showed strong blue luminescence when excited with ultraviolet light. Excitation wavelength dependent photoluminescence was observed in the obtained P-NCDs, and the relationship between the excitation and emission wavelength could be formulated as a linear function. The P-NCDs exhibit noticeable enhancement of photoluminescence after passivation and the quantum yield was as high as 18.7%. The P-NCDs also exhibited luminescence resistance to heavy metal ions to some extent. The excellent comprehensive properties enable the P-NCDs to have potential applications in detecting the polluted environment and other bio-imaging fields.