A Molecular Reporter for Visualizing Interfacial Jamming Based on An Aggregation Induced Emission Platform.

With the interfacial jamming of nanoparticles (NPs) a load-bearing network of NPs forms as the areal density of NPs increases, converting the assembly from a liquid-like to a solid-like assembly. Unlike vitrification, the lineal packing of the NPs in the network are denser, while the remaining NPs can remain in a liquid-like state. Being able to determine the point at which the assemblies jam, as opposed to vitrify, is a challenge, since both processes lead to a solid-like behavior of the assemblies. Here, we show a real-time fluorescence imaging method with a high fluorescence contrast to probe the evolution of the interfacial dynamics of NP-surfactants (NPSs) at the water/oil interface using aggregation induced emission (AIE) as a reporter for the transition of the assemblies into the jammed state. At densities where the AIEgens can move and rotate the AIEgens show typical fluorescence behavior. However, when aggregation of these fluorophores occurs, the intermolecular separation distance is sufficiently small to arrest rotation and a significant enhancement in the fluorescence intensity occurs. This fluorescence behavior provides a unique means to probe jamming behavior.