In situ XRD resolves the structural evolution of the Na–Cu/Ni/Mn–O system during the Na intercalation/deintercalation processes. The introduction of Cu2+ into the transition metal lattice is an strategy to prevent P2–O2 phase transitions.

Carbon dots (C-dots) have been proven to show the capability for direct reduction of Ag(+) to elemental silver (Ag(0)) without additional reducing agent or external photoirradiation by incubating Ag(+) with C-dots for 5 min in a water bath at 50 °C. Silver nanoparticles (Ag-NPs) are simultaneously formed with an average size of 3.1 ± 1.5 nm and grew on carbon dots. This process involves the oxidation of amine or phenol hydroxyl groups on the aromatic ring of C-dots. Meanwhile C-dots protect and stabilize the Ag-NPs from aggregation in aqueous medium; that is, the Ag-NPs are stable at least for 45 days in aqueous medium. The formed Ag-NPs cause significant resonance light scattering (RLS), which correlates closely with the concentration of silver cation, and this facilitates quantitative detection of silver in aqueous medium.

Alleviating large stress is critical for high‐energy batteries with large volume change upon cycling, yet this still presents a challenge. Here, a gradient hydrogen‐bonding binder is reported for high‐capacity silicon‐based anodes that are highly desirable for the next‐generation lithium‐ion batteries. The well‐defined gradient hydrogen bonds, with a successive bond energy of −2.88– −10.04 kcal mol−1, can effectively release the large stress of silicon via the sequential bonding cleavage. This can avoid recurrently abrupt structure fracture of traditional binder due to lack of gradient energy dissipation. Certainly, this regulated binder endows stable high‐areal‐capacity silicon‐based electrodes >4 mAh cm−2. Beyond proof of concept, this work demonstrates a 2 Ah silicon‐based pouch cell with an impressive capacity retention of 80.2% after 700 cycles (0.028% decay/cycle) based on this gradient hydrogen‐bonding binder, making it more promising for practical application.

Uncovering complex oil-water flow structure represents a challenge in diverse scientific disciplines. This challenge stimulates us to develop a new distributed conductance sensor for measuring local flow signals at different positions and then propose a novel approach based on multi-frequency complex network to uncover the flow structures from experimental multivariate measurements. In particular, based on the Fast Fourier transform, we demonstrate how to derive multi-frequency complex network from multivariate time series. We construct complex networks at different frequencies and then detect community structures. Our results indicate that the community structures faithfully represent the structural features of oil-water flow patterns. Furthermore, we investigate the network statistic at different frequencies for each derived network and find that the frequency clustering coefficient enables to uncover the evolution of flow patterns and yield deep insights into the formation of flow structures. Current results present a first step towards a network visualization of complex flow patterns from a community structure perspective.

Hollow nanostructures of metal oxides have found broad applications in different fields. Here, we reported a facile and versatile synthetic protocol to prepare hollow metal oxide nanospheres by modulating the chemical properties in solid nanoparticles. Our synthesis design starts with the precipitation of urea-containing metal oxalate, which is soluble in water but exists as solid nanospheres in ethanol. A controlled particle hydrolysis is achieved through the heating-induced urea decomposition, which transforms the particle composition in an outside-to-inside style: The reaction starts from the surface and then proceeds inward to gradually form a water-insoluble shell of basic metal oxalate. Such a reaction-induced solubility difference inside nanospheres becomes highly efficient to create a hollow structure through a simple water wash process. A following high temperature treatment forms hollow nanospheres of different metal oxides with structural features suited to their applications. For example, a high performance anode for Li-ion intercalation pseudocapacitor was demonstrated with the hollow and mesoporous NbO nanospheres.

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As table rod-like sulfonated viologen (R-Vi) derivative is developed through as patial-structure-adjustment strategy for neutral aqueous organic redoxf lowb atteries (AORFBs). The obtained R-Vifeatures four individual methyl groups on the 2,2',6,6'-positions of the 4,4'-bipyridine core ring. The tethered methyls confine the movement of the alkylc hain as well as the sulfonic anion, thus driving the spatial structure from sigmoid to rod shape.T he R-Viw ith weak charge attraction and large molecular dimension displays an ultralow membrane permeability that is only 14.7 %o ft hat of typical sigmoid viologen. Moreover,t he electron-donating effect of methyls endows R-Viw ith the lowest redox potential of À0.55 Vv s. SHE among one-electron-storage viologen-based AORFBs.The AORFB with the R-Vianolyte and aK 4 Fe(CN) 6 catholyte exhibits an energy efficiency up to 87 %a nd extremely lowc apacity-fade rate of 0.007 %p er cycle in 3200 continuous cycles.

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