Multifunctional Zn-Carbon dots enhanced specific recognition and in-situ degradation of tetracycline

Tetracycline (TC) contributes to the spread of antibiotic resistance, leading to ecological imbalances and negative environmental impacts. Achieving multifunctional applications that allow for specific recognition and in-situ degradation of tetracycline simultaneously remains a significant challenge. This study developed a series of metal-doped carbon dots, specifically zinc-doped carbon dots (Zn-CDs). The incorporation of zinc and the preservation of oxygen-containing functional groups enhance the crystallinity of the Zn-CDs' carbon core and optimize their band gap for improved light luminescence, thereby increasing the quantum yield from 14.7% to 28.6%. Moreover, Zn-CDs demonstrate precise detection of TC in complex pollutant mixtures, achieving a detection limit as low as 25 nM. The mechanism comprises the internal filtering effect attributed to spectral overlap and the electron transfer subsequent to the chelation of zinc in Zn-CDs and carbonyl oxygen in tetracycline. Due to the combination of Zn-CDs with tetracycline that brings a shorter reaction distance and the introduction of zinc that offers more active sites for the generation of free radicals, the degradation reaction likelihood is augmented. The Fenton-like and photocatalytic degradation efficiencies of Zn-CDs were raised over three times, reaching a degradation rate of TC up to 95% and showing excellent stability over five cycles. And the main degradation pathways were respectively driven by hydroxyl radicals and superoxide radicals. Thus, this research provides novel perspectives and examples for constructing multifunctional carbon dots via the metal doping method to effectively tackle environmental pollution.