Metallic nanostructures have found enormous potentials in the areas of photocatalysis, integrated nanophotonic devices, bio-sensing, bio-imaging, solar cells, surface enhanced Raman spectroscopy (SERS), etc. The key for these promising applications is to understand and manipulate the surface plasmon resonance (SPR) of the nanostructures. To this aim, Li Zhi-Yuan’s group in Institute of Physics, Chinese Academy of Sciences has made a serial of progresses in these frontier research areas.

　  The photocatalytic efficiency of TiO2 nanoparticles has played significant influences on their practical application in areas such as solar cells, sanitation, and cancer therapy. Different from most scientists focusing on the chemical or electronic side of the particles, Li’s group has physically demonstrated the scheme of boosting the photocatalytic activity of TiO2 by using the gold nanoparticles as a near-UV light harvesting agent [Opt. Lett. 35, 3402 (2010)].

　  They have experimentally explored a technique to align originally randomly oriented gold nanorods and showed that aligned gold nanorods behaved the same as a single nanorod in the response to linear polarization light. The technique can significantly eases the technical burden of exploring and probing the single particle properties. Furthermore, aligned nanorods could enhance the nonlinearity of polymer nanocomposites by more than 1-2 orders of magnitude [Appl. Phys. Lett. 96, 260103(2010)].

　  They have built an analytical solution for describing the optical bistability properties of a silver nanoantenna involving Kerr nonlinear medium in the gap of the antenna. The analytical model shows that the key factor towards a low-threshold and high-contrast optical bistability is to explore surface plasmon resonance with narrow linewidth, for instance, by introducing gain medium into the structures [Opt. Express 18, 13337(2010)].

　  To enhance the performance of SERS and other plasmonic devices, they have developed word-wide collaborations in exploring a series of topics such as the tailoring of “sea urchin”-like gold mesoparticles, the synthesis of single-crystal complex nanocrystals, the growth of transparent copper nanowires and the fabrication of ultrafine and smooth metallic nanostructures [Nano Lett. 10, 5006(2010), J. Am. Chem. Soc. 13, 8552(2010), ACS Nano 4, 6725(2010), Adv. Mater. 22, 3558(2010), Adv. Mater. 22, 4345(2010) ].

　  The work has been supported by Chinese Academy of Sciences, the National Natural Science Foundation of China, and the Chinese Ministry of Science and Technology.

Fig (Color online) Center-plane field intensity patterns for (a) a pure TiO2 particle (20 nm) at a wavelength of 150 nm and (b) the Au=TiO2 particles (TiO2 20 nm, Au 50 nm) at a wavelength of 260 nm. The coordinates are in units of micrometers, and the field intensity is in units of the incident field intensity. Note that the maximum field intensity in panel (b) is 20 times larger than in panel (a).