Gold core/silver shell (Au@Ag) nanoparticles of ~37 ± 5 nm diameter generate intense SERS (λEX=785 nm) responses in solution when they interact with the SERS labels rhodamine 6G (R6G), 4-mercaptopyridine (MPY), and 4-mercaptobenzoic acid (MBA). Herein the relationship between SERS intensity, aggregation, and adsorption phenomenon isobserved by titrating Au@Ag with the above labels. As the labels adsorb to the Au@Ag, they drive aggregation as evidenced by the creation of NIR extinction peaks, and the magnitude of this NIR extinction (measured at 830 nm) correlates very closely to magnitude of the intense SERS signals. The label MBA is an exception since it does not trigger aggregation nor does it result in intense SERS; rather intense SERS is recovered only after MBA coated Au@Ag is aggregated with KCl. An “inner filter” model is introduced and applied to compensate for solution extinction when the exciting laser radiation is significantly attenuated. This model permits a summary of the SERS responses in the form of plots of SERS intensity versus the aggregate absorption at 830 nm, which shows the excellent correlation between intense SERS and LSPR bands extinction.

Electrocatalytic synthesis of hydrogen peroxide (H 2 O 2 ) via two-electron reduction of oxygen has emerged as an effective strategy to replace the traditional anthraquinone oxidation route. Herein, copper/carbon nanocomposites are prepared by pyrolytic treatment of a metal organic framework precursor, which consists of copper oxide (CuO x ) nanoparticles dispersed within a carbon matrix, as evidenced by results from transmission electron microscopy and X-ray photoelectron spectroscopy measurements. Deliberate electrochemical activation enriches the Cu 2 O species on the nanocomposite surface and markedly enhances the performance of electrocatalytic oxygen reduction to H 2 O 2 with the selectivity increased to 68% from ca. 45% (at +0.1 V) for the as-produced counterparts. This can be exploited for the effective electrochemical degradation of methylene blue. This is accounted for by the weakened interaction with peroxide intermediates on Cu 2 O, as confirmed by results from first-principles calculations. Results from this study underline the significance of structural engineering based on electrochemical activation for the enhanced selectivity of oxygen reduction reaction for H 2 O 2 production.