분자 플라스모닉스 연구실

The goal of the Kim’s lab at SNU is to experimentally study the fundamental light-molecule-metal interaction to better understand the structure-reactivity relationship of molecules on metallic surfaces at single-molecule level. For this purpose, we study and use the plasmonics, the resonant light-metal interaction at nanoscale, to overcome the experimental limit of molecular spectroscopy, and to discover new chemical interactions at nanoscale. We have been studying the localized surface plasmons (LSPs) of individual Ag and Au nanoparticles and their close-coupling. To better understand the LSPs, we probe the plasmons in spatial domain (i. e., plasmon modes) as well as in frequency domain (i. e., resonance frequencies). In particular, we have shown that the scattering-type scanning near-field optical microscopy (sSNOM, Figure 1a) technique can be used to directly map out the plasmonic local field distribution with ~10 nm spatial resolution. We have demonstrated experimentally and theoretically that sSNOM probe can visualize the plasmonic local field around a metallic nanostructure without significant perturbation. Based on this method, we have successfully visualized the capacitively coupled mode (bonding dipole plasmon mode) of Au-nanocube dimers in real-space. Most recently, we have shown that both the mode shapes and resonance frequencies of longitudinal plasmons of heterometallic AgAuAg-nanorods are nearly uninfluenced by the presence of Ag-Au interfaces. 40 years of investigation on SERS have revealed that the SERS arise from plasmonic field enhancement (so-called the EM-mechanism) and from the chemical (charge-transfer enhancement, perturbation on molecular polarizability, and many others) mechanisms. While the two mechanism overall explain the experiment there sti