Protein-derived carbon nanodots with an ethylenediamine-modulated structure as sensitive fluorescent probes for Cu2+ detection

Abstract

The increasing use of fluorescent carbon nanodots (CNDs) demonstrates their advantages for sensing applications; these include superior photostability, absence of toxicity, and rapid analytical capability. However, CNDs usually have multiple types of functional groups covering their surfaces, which decrease their sensitivity and selectivity. In this study, the required structure of β-lactoglobulin (LG)-derived carbon nanodots was achieved by adding ethylenediamine (EDA) to the synthesis process. Due to the consumption of protein carboxyl groups during the preparation process, a homogeneous coverage of amino groups on the surfaces of the CNDs was achieved, resulting in high sensitivity of the CNDs to copper ions. Furthermore, owing to effective passivation of trap states and a high content of N doping, the as-prepared CNDs showed a high quantum yield and an excitation-independent emission property. We believe that this type of preparation method is useful for the design of protein-derived CNDs, which may have promising applications for detecting various metal ions in a biological environment.