Intrinsic Specificity of Plain Ammonium Citrate Carbon Dots for : Interfacial Mechanism, Diagnostic Translation and General Revelation

The exploitation of carbon dots (CDs) is now flourishing; however, more effort is needed to overcome their lack of intrinsic specificity. Herein, instead of synthesizing novel CDs, we reinvestigated three reported CDs and discovered that plain ammonium citrate CDs (AC-CDs) exhibited surprising specificity for . Notably, we showed that the interfacial mechanism behind this specificity was due to the affinity between the high abundant urea/ammonium transporters on outer membrane and the surface-coordinated ammonium ions on AC-CDs. Further, we justified that ammonium sulfate-citric acid CDs also possessed -specificity owing to their NH doping. Thereby, we suggested that the incorporation of a molecule that could be actively transported by abundant membrane receptors into the precursors of CDs might serve as a basis for developing a plain CD with intrinsic specificity for . Moreover, AC-CDs exhibited specificity towards live, dead, and multidrug-resistant strains. Based on the specificity, we developed a microfluidics-assisted in vitro sensing approach for , achieving a simplified, rapid and ultrasensitive detection with two procedures, shortened time within 45.0 ​min and a low actual limit of detection of 10.0 ​CFU ​mL. This work sheds light on the design of more -specific or even bacteria-specific CDs and their realistic translation into clinical practice.