Self-polymerized polydopamine-imprinted layer-coated carbon dots as a fluorescent sensor for selective and sensitive detection of 17β-oestradiol.

The compound 17β-oestradiol (E2) is a steroidal oestrogen used extensively in food processing and animal husbandry. As E2 is well-known as a typical endocrine disrupting chemical, its release, penetration, and exposure create serious environmental concerns. Carbon dots (CDs) have attracted great attention due to their excellent fluorescent and non-toxic properties. To help improve the selectivity of CDs, they can be combined with molecularly-imprinted polymers (MIPs). In light of the limitations involved in the fabrication of MIP layer on CDs (e.g., time consumption and low controllability of imprinted layer), the mussel inspired dopamine self-polymerization can be considered as an alternative option. As functional monomer in molecular imprinted technology, dopamine can be used efficiently to polymerize in weak alkaline condition (e.g., formation of polydopamine). In this research, a new method was developed for selective and sensitive fluorescent detection of E2 based on self-polymerization of dopamine (functional monomer) on fluorescent carbon dots (CDs@MI-PDA). The developed sensor selectively binds with E2 to quench the fluorescence intensity of CDs by photo-induced electron transfer. The sensor showcases a detection limit of E2 as 0.34 ng/mL with a linearity over 1-50 ng/mL. Furthermore, the probe was successfully applied to water (tap and river water) and milk samples with recoveries of 96.4-102.2 %. This study is expected to open a new path for the development of a simple and convenient detection approach for E2 present in complex matrices.