RESUMEN
Plasmonic nanoparticles have been demonstrated to enhance photocatalysis due to their strong photon absorption and efficient hot-carrier generation. However, plasmonic photocatalysts suffer from a short lifetime of plasmon-generated hot carriers that decay through internal relaxation pathways before being harnessed for chemical reactions. Here, we demonstrate the enhanced photocatalytic reduction of gold ions on gold nanorods functionalized with polyvinylpyrrolidone. The catalytic activities of the reaction are quantified by in situ monitoring of the spectral evolution of single nanorods using a dark-field scattering microscope. We observe a 13-fold increase in the reduction rate with the excitation of d-sp interband transition compared to dark conditions, and a negligible increase in the reduction rate when excited with intraband transition. The hole scavenger only plays a minor role in the photocatalytic reduction reaction. We attribute the enhanced photocatalysis to an efficient charge separation at the gold-polyvinylpyrrolidone interface, where photogenerated d-band holes at gold transfer to the HOMO of polyvinylpyrrolidone, leading to the prolonged lifetime of the electrons that subsequently reduce gold ions to gold atoms. These results provide new insight into the design of plasmonic photocatalysts with capping ligands.
RESUMEN
Passive acoustic inversion techniques for measuring gas flux into the water column have the potential to be a powerful tool for the long-term monitoring and quantification of natural marine seeps and anthropogenic emissions. Prior inversion techniques have had limited precision due to lack of constraints on the initial amplitude of a bubble's excitation following its release into the water column ( R). R is determined by observing the acoustic signal of bubbles released from sediment in a controlled experiment and its use is demonstrated by quantifying the flux from a volcanic CO2 seep offshore Panarea (Italy), improving the precision by 78%.
RESUMEN
Underwater noise from commercial shipping throughout the oceans has been increasing over the past decades and the environmental impact of this noise remains an area of great uncertainty. This has led to the measurement of noise from commercial vessels in order to understand the impacts that these vessels may engender. Hydrofoils are used by ferries in various locations around the world and locally may be a significant contributing factor of the soundscape. However, the investigation on underwater radiated noise from the activity of hydrofoils in the field has not been widely conducted. This article is an attempt to characterize the noise from hydrofoils in the field. Detailed measurements in the coastal water close to the Panarea port, Italy are reported. The investigation describes the broadband frequency spectrum with the main energy approximately centered on 30-130 Hz but covering frequencies up to tens of kHz. A key result was that the spectrum of the noise varied between the three stages (displacement, transition, and foiling) of the hydrofoils heading into or out of the port.
