Research Topic 3: Plasmonics


Under the irradiation of light, the free electrons in a metal are driven by the alternating electric field to collectively oscillate in phase with the incident light. This collective oscillation enables effective scattering and absorption of light under a resonant condition and gives metal (especially, Ag and Au) colloids their brilliant colors. Associated with electron oscillation, polarization of surface charges also occurs on the metal surface when excited by light. Unlike bulk metals, the induced charges of a nanocrystal cannot propagate as a wave along the flat surface but are confined to and concentrated on the particle surface, in which case it is called localized surface plasmon resonance (LSPR). LSPR creates intense local electric fields within a few nanometers of the particle surface. As a direct application of LSPR, this near-field effect enhances the Raman scattering cross-sections of molecules adsorbed on a nanocrystal surface, providing a “fingerprint” spectrum rich with chemical information. The ultimate goal of this research is to manipulate the LSPR properties of metal nanocrystals. Specifically, we will use a series of physical tools to understand the intrinsic features of LSPR, such as ultrafast spectroscopy and tip-enhanced Raman spectroscopy (TERS).




[1] Successive deposition of Ag on Ag nanoplates: lateral vs. vertical growth
Zeng, J.; Xia, X. (equal contribution); Rycenga, M.; Henneghan, P.; Li, Q. and Xia, Y. Angew. Chem. Int. Ed. 2011, 50, 244-249 (VIP article, it was highlighted on the frontispieces and in an accompanying article published in the same journal, 2011, 50, 992-993).

[2] Silver nanocrystals with concave surfaces and their optical and surface-enhanced Raman scattering properties
Xia, X.; Zeng, J. (equal contribution); McDearmon, B.; Zheng, Y.; Li, Q. and Xia, Y. Angew. Chem. Int. Ed. 2011, 50, 12542. (VIP article, highlighted on the inside cover).

[3] Nanocrystal-based time-temperature indicators
Zeng, J.; Roberts, S. and Xia, Y. Chem. Eur. J. 2010, 16, 12559-12563. (Highlighted on the cover)