Magnetic polaron states in photoluminescent carbon dots enable hydrogen peroxide photoproduction

Abstract

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 theoreti cally by density functional theory in combination with molecular dynamics simulations on quasi-spherical assemblies of size-variant flakelike model sys tems, revealing the importance of size dependence and interlayer effects. The formation of the spin-separated states in Asp-CDs enables the photoproduc tion of hydrogen peroxide (H2O2) from water and water/2-propanol mixture via a water oxidation reaction.