Ultrahigh-yield synthesis of N-doped carbon nanodots that down-regulate ROS in zebrafish

Oxidative damage induced by accumulation of excessive reactive oxygen species (ROS) could result in increased chronic inflammation and thus ageing and age-related diseases. Carbonaceous nanodrugs hold great promise for ameliorating age-related diseases, and it is necessary to develop ultrahigh-yield synthesis of such nanodrugs. To improve the synthetic yield (less than 50%) of carbon nanodots (CNDs), the general choice is to screen precursors. However, no reliable concept for improving the yield has been explored over the past few decades. We are the first to propose the concept of using carbon-carbon double bonds to boost the synthetic yield and demonstrate record breaking ultrahigh-yield (85.9%) synthesis of N-doped CNDs. When the C=C content increased from 14 to 56 mmol, the synthetic yield exhibited a 3.3-fold increase. Nitrogen elements are doped as pyridinic-like N and NH2, where conjugated p-systems as electron donors and pyridinic-like structures would benefit the potential down-regulated effect for ROS. N-doped CNDs exhibit an outstanding protective effect against oxidative stress via inhibiting exogenous and endogenous ROS generation, where the ROS in zebrafish are significantly reduced by 68%. Hence the concept of carbon-carbon double bond-boosted ultrahigh-yield synthesis of N-doped CNDs provides a promising strategy to be employed for carbonaceous nanodrugs aiming at preventing and curing ageing and age-related diseases.