Nanoparticle surfactants for kinetically arrested photoactive assemblies to track light-induced electron transfer

Small semiconductor nanocrystals control the assembly of larger plasmonic nanostructures through interfacial self-limiting aggregation, leading to permeable and colloidally stable photoactive hybrids for photocatalysis and tracking of light-induced electron transfer. Nature controls the assembly of complex architectures through self-limiting processes; however, few artificial strategies to mimic these processes have been reported to date. Here we demonstrate a system comprising two types of nanocrystal (NC), where the self-limiting assembly of one NC component controls the aggregation of the other. Our strategy uses semiconducting InP/ZnS core-shell NCs (3 nm) as effective assembly modulators and functional nanoparticle surfactants in cucurbit[n]uril-triggered aggregation of AuNCs (5-60 nm), allowing the rapid formation (within seconds) of colloidally stable hybrid aggregates. The resultant assemblies efficiently harvest light within the semiconductor substructures, inducing out-of-equilibrium electron transfer processes, which can now be simultaneously monitored through the incorporated surface-enhanced Raman spectroscopy-active plasmonic compartments. Spatial confinement of electron mediators (for example, methyl viologen (MV2+)) within the hybrids enables the direct observation of photogenerated radical species as well as molecular recognition in real time, providing experimental evidence for the formation of elusive sigma-(MV+)(2) dimeric species. This approach paves the way for widespread use of analogous hybrids for the long-term real-time tracking of interfacial charge transfer processes, such as the light-driven generation of radicals and catalysis with operando spectroscopies under irreversible conditions.

Automated summary

The study demonstrates the use of semiconductor nanocrystals to control the self-limiting aggregation of larger nanostructures, leading to stable photoactive hybrids for photocatalysis. Real-time monitoring of electron transfer processes and catalysis under irreversible conditions is now possible through this approach.