Efficient Charge Dynamics in Carbon Nanodot-Methyl Viologen Systems: Ultrafast Electron Transfer and Suppressed Recombination

Electron transfer (ET) processes at donor–acceptor interfaces are pivotal for advancing the efficiency of energy conversion devices and photocatalytic systems. This study investigates the ultrafast electron transfer dynamics and subsequent charge recombination mechanisms within a carbon nanodot (CND) and methyl viologen (MV²⁺) system. This interface holds significant promise due to its demonstrated capacity for efficient charge separation and remarkably slow charge recombination. The intense interaction between CNDs and MV²⁺ is primarily governed by electrostatic attraction, which facilitates their proximity and, consequently, highly efficient electron transfer. Our findings reveal that photoexcited CNDs transfer electrons to MV²⁺ within an exceptionally rapid time scale of ∼1 ps. Crucially, this leads to the formation of long-lived MV^•+ radical cations, with charge recombination occurring on a significantly slower time scale of ca. 0.7 μs. This research provides profound insights into the fundamental mechanisms governing interfacial electron transfer in CND-MV²⁺ systems, thereby paving the way for optimizing their applications across various photocatalytic and energy-conversion technologies. A deeper understanding of these charge dynamics is essential for developing next-generation materials with better performance in renewable energy and environmental applications.