Optically Encoded Nanodots for Logic-Gated Sensing and Antioxidant Defense

Optically encoded nanodots have emerged as versatile materials with significant potential for environmental and biomedical applications. This study presents ruthenium-doped carbon dots (Ru-CDs) synthesized from urea and citric acid doped with ruthenium to enhance their properties. These Ru-CDs exhibited a QY of 34.5% and demonstrated dual-mode "turn-on/turn-off/turn-on" sensing for lead ions (Pb²⁺) and cysteine, with a limit of detection (LOD) of 14.5 and 197 pM, respectively. In addition to their sensing abilities, the Ru-CDs functioned as nanozymes, exhibiting catalase-like activity by decomposing hydrogen peroxide into water and oxygen. The Ru-CDs exhibited potent antioxidant properties by effectively neutralizing reactive oxygen species (ROS), thereby reducing oxidative stress in cells. Furthermore, their antioxidant capacity was evaluated in the context of food preservation. These multifunctional Ru-CDs, with their remarkable sensing, enzyme mimic, antioxidant, and preservative properties, offer promising applications in environmental monitoring, health protection, and food preservation.