Plasmonic nanoantennas focus light below the diffraction limit, creating strong field enhancements, typically within a nanoscale junction. Placing a nanostructure within the junction can greatly enhance the nanostructure’s innate optical absorption, resulting in intense photothermal heating that could ultimately compromise both the nanostructure and the nanoantenna. Here, we demonstrate a three-dimensional “antenna-reactor” geometry that results in large nanoscale thermal gradients, inducing large local temperature increases in the confined nanostructure reactor while minimizing the temperature increase of the surrounding antenna. The nanostructure is supported on an insulating substrate within the antenna gap, while the antenna maintains direct contact with an underlying thermal conductor. Elevated local temperatures are quantified, and high local temperature gradients that thermally reshape only the internal reactor element within each antenna-reactor structure are observed. We also show that high local temperature increases of nominally 200 °C are achievable within antenna-reactors patterned into large extended arrays. This simple strategy can facilitate standoff optical generation of high-temperature hotspots, which may be useful in applications such as small-volume, high-throughput chemical processes, where reaction efficiencies depend exponentially on local temperature.

Water production from solar thermal desalination is limited by the energy consumption of phase change. Resonant heat exchange between matched saline feed and purified distillate flow rates enables optimized recovery of vaporization energy.

Perfluorooctanoic acid (PFOA) is a widely distributed recalcitrant contaminant. In recent years, advanced oxidation processes have been explored for PFOA degradation, yet factors influencing their efficacy and degradation mechanism are not fully understood. Here, we resolve ambiguity in the literature regarding the role of superoxide in PFOA degradation (e.g., by nucleophilic attack) by considering three pure superoxideproducing systems: KO 2 in dimethyl sulfoxide, xanthine oxidase with hypoxanthine, and WO x /ZrO 2 catalyst with H 2 O 2 . Superoxide production was confirmed in all systems by electron paramagnetic resonance spectroscopy and by precipitation of nitroblue tetrazolium, a common superoxide probe. Positive control experiments showed that the produced superoxide degrades ∼48% of bisphenol A within 1 day, corroborating the fact that superoxide was sufficiently stable and available for reaction in the test systems. However, no PFOA degradation was observed, which was corroborated by the absence of fluoride and degradation byproducts in all three systems. Therefore, other reaction pathways should be explored for PFOA degradation.