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Surface plasmon resonances (SPRs) have been found to promote chemical reactions. In most oxidative chemical reactions oxygen molecules participate and understanding of the activation mechanism of oxygen molecules is highly important. For this purpose, we applied surface-enhanced Raman spectroscopy (SERS) to find out the mechanism of SPR-assisted activation of oxygen, by using p-aminothiophenol (PATP), which undergoes a SPR-assisted selective oxidation, as a probe molecule. In this way, SPR has the dual function of activating the chemical reaction and enhancing the Raman signal of surface species. Both experiments and DFT calculations reveal that oxygen molecules were activated by accepting an electron from a metal nanoparticle under the excitation of SPR to form a strongly adsorbed oxygen molecule anion. The anion was then transformed to Au or Ag oxides or hydroxides on the surface to oxidize the surface species, which was also supported by the heating effect of the SPR. This work points to a promising new era of SPR-assisted catalytic reactions. [ABSTRACT FROM AUTHOR]

Abstract: The accurate description of the energy and/or charge transfer mechanism involving Localized Surface Plasmon Resonance (LSPR) is crucial for the research field of plasmonics. The investigation is however frequently hampered by the inaccurate definition of separation distance between the energy and/or charge donor–acceptor pair. Herein we designed and constructed core–shell plasmonic nanostructures to realize precise, long separation distance control between the gold core (energy acceptor) and fluorophores (energy donor). Both steady-state and time-resolved fluorescence measurements were employed to investigate radiative properties of the as-prepared nanosystem. The observed overall fluorescence quenching of the core–shell plasmonic nanocomposites with the decrease of shell thickness is attributed to a concurrent increase of nonradiative rates and decrease of radiative rates with the separation distance decrease. However, neither fluorescence resonance energy transfer (FRET) nor nanometal surface energy transfer (NSET) model is suitable for describing the fluorescence quenching efficiency as a function of separation distance reported in this article. Remarkably, a long-range fluorescence quenching distance of over 34nm is observed, possibly arising from the coincidence of fluorophore emission wavelength with the plasmon resonance of the gold nanoparticles. This study not only gains insight for designing novel plasmonic devices, but also provides new thoughts for investigation on molecular ruler on a larger measurement scale, molecular beacons and new generation photovoltaics. [Copyright &y& Elsevier]