Insight into ultrasensitive and high-stability flocculation-enhanced Raman spectroscopy for the in situ noninvasive probing of cupping effect substances

The aggregation of nanoparticles is the key factor to form hot spots for the flocculation-enhanced Raman spectroscopy (FLERS) method. However, the structure of flocculation is still not clear. It is therefore necessary to explore and analyze the aggregation process of nanoparticles more carefully, so as to realize a better application of FLERS. Here, we report the application of in situ liquid cell transmission electron microscopy (TEM) combined with an in situ high-speed camera to analyze the particle behaviors. The results showed that flocculation can exist stably and the gap between the nanoparticles in the flocculation always remained at 7-9 nm, which ensured the high stability and sensitivity of the FLERS method. We successfully applied FLERS to the in situ noninvasive probing of cupping effect substances. The results indicated the scientific principle behind the traditional Chinese medicine method to some extent, which thus provides a new and effective method for the in situ dynamic monitoring of biological systems.

Automated summary

The aggregation of nanoparticles is crucial for the formation of hot spots in the flocculation-enhanced Raman spectroscopy (FLERS) method. This study utilized in situ liquid cell transmission electron microscopy (TEM) coupled with an in situ high-speed camera to analyze the particle behaviors during flocculation. The results demonstrated the stable existence of flocculation with nanoparticles positioned at a gap of 7-9 nm, which ensured the high stability and sensitivity of the FLERS method. FLERS was successfully applied for the in situ noninvasive probing of cupping effect substances, providing insights into the scientific principle behind traditional Chinese medicine.