Magnetic Polaron States in Photoluminescent Carbon Dots Enable Hydrogen Peroxide Photoproduction

Photoactivation of aspartic acid‐based carbon dots (Asp‐CDs) induces the generation of spin‐separated species, including electron/hole (e−/h+) polarons and spin‐coupled triplet states, as uniquely confirmed by the light‐induced electron paramagnetic resonance spectroscopy. The relative population of the e−/h+ pairs and triplet species depends on the solvent polarity, featuring a substantial stabilization of the triplet state in a non‐polar environment (benzene). The electronic properties of the photoexcited Asp‐CDs emerge from their spatial organization being interpreted as multi‐layer assemblies containing a hydrophobic carbonaceous core and a hydrophilic oxygen and nitrogen functionalized surface. The system properties are dissected theoretically by density functional theory in combination with molecular dynamics simulations on quasi‐spherical assemblies of size‐variant flakelike model systems, revealing the importance of size dependence and interlayer effects. The formation of the spin‐separated states in Asp‐CDs enables the photoproduction of hydrogen peroxide (H2O2) from water and water/2‐propanol mixture via a water oxidation reaction. Carbon dots synthesized from aspartic acid not only provide highly emissive photoluminescent units upon excitation but also express long‐lived magnetic electron/hole polaron states. The formation of these highly reactive spin‐separated species arises from the spatial anisotropy of Asp‐CDs and enables the photoproduction of H2O2 via the water oxidation reaction.