SERS and NMR Studies of Typical Aggregation-Induced Emission Molecules

Over recent decades, aggregation-induced emission (AIE) molecules have attracted increasing attention. Restriction of intramolecular rotation (RIR) has been widely accepted as the cause of the emission when AIE molecules aggregate into clusters. The intramolecular rotation of AIE molecules can be monitored by molecular vibration spectra such as nuclear magnetic resonance (NMR), infrared, and Raman, especially surface-enhanced Raman scattering (SERS) which has high sensitivity down to a single molecule. We employed SERS and NMR to study the AIE emission mechanism and compared experimental results with simulation data to monitor the RIR. Interestingly, we found that intramolecular rotation was also restricted for individual AIE molecules loaded onto SERS substrate surfaces due to the laid-down configuration.