Z. L. Yang

“Smart” Ag Nanostructures for Plasmon-Enhanced Spectroscopies

Silver is an ideal candidate for surface plasmon resonance (SPR)-based applications because of its great optical cross-section in the visible region. However, the uses of Ag in plasmon-enhanced spectroscopies have been limited due to their interference via direct contact with analytes, the poor chemical stability, and the Ag(+) release phenomenon. Herein, we report a facile chemical method to prepare shell-isolated Ag nanoparticle/tip. The as-prepared nanostructures exhibit an excellent chemical stability and plasmonic property in plasmon-enhanced spectroscopies for more than one year. It also features an alternative plasmon-mediated photocatalysis pathway by smartly blocking hot electrons. Astonishingly, the shell-isolated Ag nanoparticles (Ag SHINs), as smart plasmonic dusts, reveal a ∼1000-fold ensemble enhancement of rhodamine isothiocyanate (RITC) on a quartz substrate in surface-enhanced fluorescence. The presented smart Ag nanostructures offer a unique way for the promotion of ultrahigh sensitivity and reliability in plasmon-enhanced spectroscopies.

Adsorption and photon-driven charge transfer of pyridine on a cobalt electrode analyzed by surface enhanced Raman spectroscopy and relevant theories

Surface enhanced Raman spectroscopy (SERS) has been applied to study the interaction of pyridine with a cobalt electrode surface. A set of good quality SERS spectra was obtained by using an appropriate surface-roughening procedure and a highly sensitive confocal Raman microscope. The surface enhancement factor was about three orders of magnitude calculated from experimental data and analyzed by the relevant theories. The electromagnetic contribution accounts for two out of the three orders of magnitude mainly through the lightning-rod effect. The remaining enhancement originates from the photon-driven charge transfer mechanism. The SERS intensity-potential profile shows the existence of two charge transfer processes. One is the excitation of the metal 4s orbital to the mixing orbital of the metal 4px and p-type 3b1 of pyridine, and the other is from the metal 3d orbital to the p-type 2a2 orbital of pyridine. Furthermore, the spectral difference for the adsorbed pyridine on cobalt and silver surfaces indicates that the chemical interaction of pyridine with the former is considerably stronger than the latter. # 2003 Elsevier B.V. All rights reserved.

Plasmon‐Enhanced Spectroscopies with Shell‐Isolated Nanoparticles

Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), due to its versatility, has been able to break the long-term limitations of the material- and substrate-specific generalities in the traditional field of surface-enhanced Raman spectroscopy. With a shell-isolated work principle, this method provides an opportunity to investigate successfully in surface, biological systems, energetic materials, and environmental sciences. Both the shell material and core morphology are being improved continuously to meet the requirements in diverse systems, such as the electrochemical studies at single crystal electrode surfaces, in situ monitoring of photoinduced reaction processes, practical applications in energy conversion and storage, inspections in food safety, and the surface-enhanced fluorescence. Predictably, the concept of shell-isolated nanoparticle-enhancement could be expanded to the wider range for the performance of plasmon-enhanced spectral modifications.