Extracellular polymeric substances play important roles in microbial extracellular electron transfer processes.

Apoferritin derived from the native protein ferritin was employed to encapsulate anticancer drugs cisplatin and carboplatin.

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The utilization of redox-active organic species in aqueous redox flow batteries holds great promise for large-scale and sustainable energy storage. Herein, we report the low-temperature green synthesis of three different phenazine derivatives and investigate their performances in alkaline organic redox flow batteries. Electrochemical characterizations reveal that the ortho-substituents of the hydroxyl groups in phenazine derivatives have significant influences on the battery performances. By introducing an additional phenyl group adjacent to the hydroxyl group in the phenazine motif and a carboxyl group with strong solubilizing effect, the redox flow battery based on fused-ring benzo­[a]­hydroxyphenazine-7/8-carboxylic acid with 1.0 M electron concentration exhibits greatly improved capacity retention rate of 99.986% cycle–1 (99.92% day–1) and stable average energy efficiency of ∼80% for over 1300 cycles. Moreover, a combinatorial library of hydroxyphenazine derivatives with varying substituent groups was built, and their redox properties were simulated to guide further molecular structure design of phenazine-derived electroactive compounds.

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Aqueous redox flow batteries (ARFBs) based on the electrolyte solutions of redox-active organic molecules are very attractive for the application of large-scale electrochemical energy storage. We propose a high-performance ARFB system utilizing 2hydroxy-3-carboxy-1,4-naphthoquinone (2,3-HCNQ) and K 4 Fe-(CN) 6 as the anolyte and catholyte active species, respectively. The 2,3-HCNQ molecule exhibits high solubility and can carry out a reversible two-electron redox process with rapid redox kinetics. The assembled 2,3-HCNQ/K 4 Fe(CN) 6 ARFB delivered a cell voltage of 1.02 V and realized a peak power density of 0.255 W cm −2 . The 2,3-HCNQ/K 4 Fe(CN) 6 ARFB can be stably operated at a current density of 100 mA cm −2 for long-term cycling (with a capacity retention of ∼94.7% after 100 cycles).

Polynuclear copper complexes with two or three Cu(BPA) (BPA, bis(2-pyridylmethyl)amine) motifs, [Cu2(mTPXA)Cl4]3 H2O (1), [Cu2(pTPXA)Cl4]3 H2O (2), [Cu3(HPTAB)Cl5]Cl3 H2O (3) (mTPXA = N,N,N',N'-tetra-(2-pyridylmethyl)-m-xylylene diamine; pTPXA = N,N, N',N'-tetra-(2-pyridylmethyl)-p-xylylenediamine; HPTAB = N,N,N',N',N'',N''-hexakis(2-pyridylmethyl)-1,3,5-tris-(aminomethyl)benzene) have been synthesized and characterized. The crystal structures of compounds 2 and 3 showed each Cu(BPA) motif had a 4+1 square-pyramidal coordination environment with one chloride occupying the apical position and three N atoms from the same BPA moiety together with another Cl atom forming the basal plane. Fluorescence and circular dichroism (CD) spectroscopy studies indicated that the DNA binding followed an order of 3>2>1 in the compounds. These complexes cleave plasmid pUC19 DNA by using an oxidative mechanism with mercaptopropionic acid (MPA) as the reductant under aerobic conditions. Dinuclear Cu2+ complexes 1 and 2 showed much higher cleavage efficiency than their mononuclear analogue [Cu(bpa)Cl2] at the same [Cu2+] concentration, suggesting a synergistic effect of the Cu2+ centers. Moreover, the meta-dicopper centers in complex 1 facilitated the formation of linear DNA. Interestingly, the additional copper center to the meta-dicopper motif in complex 3 decreased the cleavage efficacy of meta-dicopper motif in complex 1, although it is able to cleave DNA to the linear form at higher [Cu2+] concentrations. Therefore, the higher DNA binding ability of complex 3 did not lead to higher cleavage efficiency. These findings have been correlated to the DNA binding mode and the ability of the Cu2+ complexes to activate oxygen (O2). This work is a good example of the rational design of multinuclear Cu2+ artificial nuclease and the activity of which can be manipulated by the geometry and the number of metal centers.

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