Comprehensively active condensed water from vapors of plasmon-activated water

Abstract Water is the most environmentally friendly solvent, but bulk water is conventionally considered to be a bystander in reactions performed in it. For decades, scientists have been discussing the characteristics of water that differ from bulk water in special environments. Recently, various small amounts of treated water were developed to create specific applications. In 2014, comprehensively active and stable plasmon-activated water (PAW), which was mass-produced and innovatively created by utilizing hot electron transfer (HET) from gold nanoparticles (AuNPs), was first reported. In this work, we report the maintenance of activity of purified Au-free PAW collected from water condensed from PAW vapor (PAW-V). Interestingly, the metastable PAW-V was still active with a structure of electron-doping and reduced hydrogen bonding (HB), which were confirmed by zeta potentials and the nuclear magnetic resonance (NMR) relaxation time (T1). Like PAW, PAW-V enhanced hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs), compared to deionized water (DIW). The PAW-V itself exhibited the ability to more rapidly evaporate due to reduced HBs between homogeneous molecules, while a PAW/isopropanol solution evaporated more slowly due to enhanced HBs between heterogeneous molecules. Also, PAW-V could scavenge free 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and reduce the strong KMnO4 oxidant. The unique properties of PAW-V were maintained after storage for 3 days at room temperature in the dark. The condensed Au-free PAW has emerged as a promising green active solvent applicable in various fields of physics, chemistry and biomedicine.