A novel light-induced reversible self-assembly (LIRSA) system is based on the reversible photodimerization and photocleavage of coumarin groups on the surface of gold nanoparticles (AuNPs) in THF solution. Facilitated by coumarin groups, light irradiation at 365 nm triggers the stable assembly of monodisperse AuNPs; the resulting self-assembly system can be disassembled back to the disassembled state by a relatively short exposure to benign UV light. The reversible self-assembly cycle can be repeated 4 times. A specific concentration range of coumarin ligand and the THF solvent were identified to be the two predominant factors that contribute to the LIRSA of AuNPs. This is the first successful application of reversible photodimerization based on a coumarin derivative in the field of AuNP LIRSA. This LIRSA system may provide unique opportunities for the photoregulated synthesis of many adjustable nanostructures and devices.

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It is a challenge to synthesize highly efficient nonprecious metal electrocatalysts with a well-defined nanostructure and rich active species. Herein, through electron engineering and structure manipulation simultaneously, we constructed Fe-embedded pyridinic-N-dominated carbon nanotubes (CNTs) on ordered mesoporous carbon, showing excellent oxygen reduction reaction activity (half-wave potential, 0.85 V) and an overpotential of 420 mV to achieve 10 mA cm–2 for oxygen evolution reaction in alkaline media (potential difference, 0.80 V). Density functional theory calculation indicates those Fe@N4 clusters improve charge transfer and further promote the electrocatalytic reactivity of the functionalized region in CNTs. Rechargeable Zn–air batteries were assembled, displaying robust charging–discharging cycling performance (over 90 h) with voltage gap of only 0.08 V, much lower than that of the Pt/C + Ir/C electrode (0.29 V). This work presents a highly active nonprecious metal-based bifunctional catalyst toward air electrode for energy conversion.

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An esterase PE10 (279 aa) from Pelagibacterium halotolerans B2(T) was cloned and overexpressed in Escherichia coli Rosetta in a soluble form. The deduced protein was 29.91 kDa and the phylogenetic analysis of the deduced amino acids sequence showed it represented a new family of lipolytic enzymes. The recombinant protein was purified by Ni-NTA affinity chromatography column and the characterization showed its optimal temperature and pH were 45 °C and pH 7.5, respectively. Substrate specificity study showed PE10 preferred short chain p-nitrophenyl esters and exhibited maximum activity toward p-nitrophenyl acetate. In addition, PE10 was a halotolerant esterase as it was still active under 4 M NaCl. Three-dimensional modeling of PE10 suggested that the high negative electrostatic potential on the surface may relevant to its tolerance to high salt environment. With this halotolerance property, PE10 could be a candidate for industrial use.