Heteronuclear double-atom catalysts, unlike single atom catalysts, may change the charge density of active metal sites by introducing another metal single atom, thereby modifying the adsorption energies of reaction intermediates and increasing the catalytic activities. First, density functional theory calculations are used to figure out the best combination by modeling two transition-metal atoms from Fe, Co, and Ni onto N-doped graphene. Generally, Fe and Co sites are highly active for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), respectively. The combination of Co and Fe to form CoFe–N–C not only further improves the Fe’s ORR and Co’s OER activities but also greatly enhances the Co site’s ORR and Fe site’s OER activities. Then, we synthesize the CoFe–N–C by a two-step pyrolysis process and find that the CoFe–N–C exhibits exceptional ORR and OER electrocatalytic activities in alkaline media, significantly superior to Fe–N–C and Co–N–C and even commercial catalysts.

A new strategy for in situ formation and separation of fluorescent N-GQDs for Fe3+ sensing was developed, with MOFs as precursors.

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Single‐atom cobalt‐based CoNC are promising low‐cost electrocatalysts for oxygen reduction reaction (ORR). However, further increasing the single cobalt‐based active sites and the ORR activity remain a major challenge. Herein, an acetate (OAc) assisted metal–organic framework (MOF) structure‐engineering strategy is developed to synthesize hierarchical accordion‐like MOF with higher loading amount and better spatial isolation of Co and much higher yield when compared with widely reported polyhedron MOF. After pyrolysis, the accordion‐structured CoNC (CoNC (A)) is loaded with denser CoN4 active sites (Co: 2.88 wt%), approximately twice that of Co in the CoNC reported. The presence of OAc in MOF also induces the generation of big pores (5–50 nm) for improving the accessibility of active sites and mass transfer during catalytic reactions. Consequently, the CoNC (A) catalyst shows an admirable ORR activity with a E1/2 of 0.89 V (40 mV better than Pt/C) in alkaline electrolytes, outstanding durability, and absolute tolerance to methanol in both alkaline and acidic media. The CoNC‐based Zn‐air battery exhibits a high specific capacity (976 mAh g−1Zn), power density (158 mW cm−2), rate capability, and long‐term stability. This work demonstrates a reliable approach to construct single atom doped carbon catalysts with denser accessible active sites through MOF structure engineering.

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The interaction, including the adsorption and embedding, of a widely applied anticancer drug, doxorubicin, with a lipid membrane was investigated. Second harmonic generation and two photon fluorescence were used as a powerful combination capable in revealing this dynamic process at the interface. The adsorption, association, deassociation and embedding of doxorubicin on the lipid membrane were clearly identified based on the consistency in the dynamic parameters revealed by the time dependent second harmonic generation and two-photon fluorescence measurements. This work also presents a new approach for in situ measurement of the adsorption density of doxorubicin on lipid membrane, benefiting from the two-photon fluorescence signal of doxorubicin being significantly altered by its chemical environment. The analysis of the location and molecular density based on the fluorescent efficiency of the chromophores makes the fluorescence measurement a “surface sensitive” technique as well. The analytical procedures used in this work are expected to aid in understanding the interaction between fluorescent molecules and lipid membranes in general.

Zn-based aqueous rechargeable batteries are promising in portable electronics because of their high voltage, low cost, etc. However, most conventional aqueous electrolytes are liable to freeze at low temperature and are incompatible with high ion concentrations, which hinders their application. Herein, we developed a sodium polyacrylate hydrogel (PANa) to superabsorb highly concentrated ions. Unprecedentedly, the hydrogel electrolyte can be stretched over ten times at −50 °C without any freezing. Therefore, the fabricated rechargeable NiCo//Zn battery worked well in a wide-temperature-range (−20 to 50 °C). This work creates many opportunities for the development and practical application of aqueous batteries.