Nanoparticle surfactants for kinetically arrested photoactive assemblies to track 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 comprised of two types of nanocrystals (NCs), 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 func- tional nanoparticle surfactants in cucurbit[n]uril-triggered aggregation of AuNCs (5-60 nm) allowing rapid formation (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 SERS–active plasmonic compartments. Spatial confinement of electron mediators (e.g. 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 σ–(MV+)2 dimeric species for the first-time. This approach paves the way for widespread use of analogous hybrids for long-term real-time tracking of interfacial charge-transfer processes, such as light-driven generation of radicals and catalysis with operando spectroscopies under irreversible conditions