Surface chemistry tuning the selectivity of carbon nanodots towards Hg²⁺ recognition

Fluorescence quenching of carbon nanodots by metal ions has been extensively applied for the determination of oligonucleotides, proteins, small molecules and metal ions. However, the problem of poor selectivity originating from the coordination of surface oxygen-containing groups to many kinds of metal ions has limited the prosperity of carbon nanodots in detection field. Herein, the specific recognition of carbon nanodots to Hg²⁺ is controlled by rational regulation of the surface structure of carbon nanodots. Passivation of the surface carboxyl and hydroxyl groups plays a decisive role in inhibiting the binding of metal ions with carbon nanodots. Upon the attachment of Hg²⁺ specific recognition unit, carbon nanodots exhibited a high selectivity to Hg²⁺. This work facilitates to rationally design the surface structure of carbon nanodots to obtain the desirable selective recognition ability.