pH-Selective Fluorescent Probe with Photothermal Ablation of Bacteria Based NIR Dye-Embedded Zwitterionic Carbon Dots

We developed a highly pH-sensitive fluorescent carbon dot probe containing IR825 photothermal dye for rapid detection of environmental bacteria, with subsequent killing activity via near-infrared (NIR) driven photothermal ablation. The IR825-loaded fluorescent carbon dot (I-CD) interacted strongly with the negative charge of bacterial surface, expressed via fluorescence ON/OFF behavior under a broad range of pH conditions, by modifying the zwitterionic conformation of the carbon dot. In acidic and basic conditions, I-CD is activated, losing its hydrophobicity in neutral condition and releasing IR825, inducing NIR-mediated photothermal activity. Release of IR825 from the I-CD core contributed to high thermal conversion, killing bacterial cells with 99% efficiency. This material shows potential to be used as a convenient, rapid, low-cost, high-sensitivity fluorescent bacterial biosensor, combined with effective bacterial killing activity via photothermal conversion with pH and NIR triggers.