Surface-enhanced Raman spectroscopy (SERS) is a powerful technique that yields fingerprint vibrational information with ultra-high sensitivity. However, only roughened Ag, Au and Cu surfaces can generate strong SERS effect. The lack of materials and morphology generality has severely limited the breadth of SERS practical applications on surface science, electrochemistry and catalysis.
Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was therefore invented to break the long-standing limitation of SERS. In SHINERS, Au@SiO2 core-shell nanoparticles were rationally designed. The gold core acts as plasmonic antenna and encapsulated by an ultra-thin, uniform and pinhole-free silica shell, can provide high electromagnetic field to enhance the Raman signals of probed molecules. The inert silica shell acts as tunneling barrier prevents the core from interacting with the environment.
SHINERS has already been applied to a number of challenging systems, such as hydrogen and CO on Pt(hkl) and Rh(hkl), which can’t be realized by traditional SERS. Combining with electrochemical methods, we has investigated the adsorption processes of pyridine at the Au(hkl) single crystal/solution interface, and in-situ monitored the surface electro-oxidation at Au(hkl) electrodes. These pioneering studies demonstrate convincingly the ability of SHINERS in exploring correlations between structure and reactivity as well as in monitoring intermediates at the interfaces. SHINERS was also explored from semiconductor surface for industry, to living bacteria for life science, and to pesticide residue detection for food safety. The concept of shell-isolated nanoparticle-enhancement is being applied to other spectroscopies such as infrared absorption, sum frequency generation and fluorescence.
Jian-Feng Li et al., Nature, 2010, 464, 392-395.
ZnO nano films were deposited on SiO2/P-Si (100) by RF magnetron sputtering. The interrelationships among growth conditions, crystal structures, and optical properties of the ZnO films were discussed. The reflection spectra of the films reveal that the band-gap of the films is between 3.2-3.3eV. The photoluminescence spectra provide further evidence for the relation between the green emission of ZnO films and the oxygen vacancy or Zn interstitial related defects. The results also demonstrate that the UV emission of ZnO is dependent on the size of the nano-crystallites forming the films. By comparing with the photoluminescence spectra at low temperature, the possible mechanism for this dependent relation was discussed.
By using Surface-Enhanced Raman Scattering, we studied the orientation of liquid crystal 5CB absorbed on nano-roughened Ag and Au electrodes. Our results firstly suggest that the orientation of LC 5CB absorbed on nano-roughened Ag electrode is different from that of Au electrode. This implies that the interaction between LC 5CB and Ag is different from the interaction between LC 5CB and Au. The conclusion is that the orientation of LC 5CB absorbed on nano-roughened Ag electrode is perpendicular, and the orientation of LC 5CB absorbed on nano-roughened Au electrode is more complicated, including parallel, perpendicular and tilted.