Interactions between oxygen and gold surfaces are fundamentally important in diverse areas of science and technology. In this work, an oxygen dimer structure was observed and identified on gold nanoparticles in catalytic decomposition of hydrogen peroxide to oxygen and water. This structure, which is different from isolated atomic or molecular oxygen surface structures, was observed with in situ surface-enhanced Raman spectroscopic measurements and identified with density functional theory calculations. The experimental measurements were performed using monodisperse 5, 50 and 400 nm gold particles supported on silica with liquid-phase hydrogen and deuterium peroxides at multiple pH values. The calculations show that on surfaces with coordinatively unsaturated gold atoms, two oxygen atoms preferentially share a gold atom with a bond distance of 0.194-0.196 nm and additionally bind to two other surface gold atoms with a larger bond distance of 0.203-0.213 nm, forming an Au-O-Au-O-Au structure. The formation of this structure depends on reaction rates and conditions.

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Summary The present study is aimed to evaluate the effect of three different drying methods, including shade drying (SD), freeze drying (FD) and hot air dying (HAD), on the chemical components, antioxidant and cytoprotective activities of aqueous‐methanol extracts from A. fragrans leaves. The total phenolic and flavonoid content were determined by spectroscopic methods, whereas the chemical profile of different extracts was determined by ultra‐high‐performance liquid chromatography coupled with a tandem mass spectrometry (UHPLC‐MS/MS). A total of thirteen compounds were characterised and 9 phenolic compounds have been quantified. Two dihydrochalcone glycosides named confusoside and vacciniifolin were found to be the most abundant phenolic compounds in the SD extract of A. fragrans leaves, which also showed the strongest antioxidant and cytoprotective activities. The results showed that shade drying is an efficient method for preserving the chemical constituents and maintaining the antioxidant and cytoprotective activities of A. fragrans leaves.

Hollow carbon fibers (aCFs) with a high specific surface area are applied as conductive scaffolds for polyaniline (PANi) growth. aCFs oxidized by HNO3 treatment have more surface negative charges, which interact with protonated aniline molecules in acidic media. The subsequent chemical oxidative polymerization assisted by (NH4)2S2O8 yields aCF–PANi composites with PANi nanorod arrays strongly coupled on both the external and internal surfaces of the aCFs. Serving as binder‐free supercapacitor electrode, the aCF–PANi composite with 31 wt % PANi exhibits a specific capacitance of 364 F g−1, and retains 70 % of this value at 20 A g−1. More interestingly, it exhibits excellent cycling stability with 92.5 % capacitance retention, and outstanding reversibility with 98.6 % coulombic efficiency, even after 5000 continuous cycles; this performance is far superior to that of both aCF and PANi electrodes. The strongly coupled PANi arrays on the aCF surface greatly reduce the interface resistance, thus facilitating both ion and electron transport for enhanced capacitive performance.

Interactions between oxygen and gold surfaces are fundamentally important in diverse areas of science and technology.I nt his work, an oxygen dimer structure was observed and identified on gold nanoparticles in catalytic decomposition of hydrogen peroxidetooxygen and water.This structure,which is different from isolated atomic or molecular oxygen surface structures,w as observed with in situ surfaceenhanced Raman spectroscopic measurements and identified with density functional theory calculations.T he experimental measurements were performed using monodisperse 5, 50 and 400 nm gold particles supported on silica with liquid-phase hydrogen and deuterium peroxides at multiple pH values.The calculations showthat on surfaces with coordinatively unsaturated gold atoms,two oxygen atoms preferentially share agold atom with abond distance of 0.194-0.196 nm and additionally bind to two other surface gold atoms with al arger bond distance of 0.203-0.213 nm, forming an Au-O-Au-O-Au structure.T he formation of this structure depends on reaction rates and conditions.