Here we report InAs nanowire (NW) near-infrared photodetectors having a detection wavelength up to ∼1.5 μm. The single InAs NW photodetectors displayed minimum hysteresis with a high Ion/Ioff ratio of 10(5). At room temperature, the Schottky-Ohmic contacted photodetectors had an external photoresponsivity of ∼5.3 × 10(3) AW(-1), which is ∼300% larger than that of Ohmic-Ohmic contacted detectors (∼1.9 × 10(3) AW(-1)). A large enhancement in photoresponsivity (∼300%) had also been achieved in metal Au-cluster-decorated InAs NW photodetectors due to the formation of Schottky junctions at the InAs/Au cluster contacts. The photocurrent decreased when the photodetectors were exposed to ambient atmosphere because of the high surface electron concentration and rich surface defect states in InAs NWs. A theoretical model based on charge transfer and energy band change is proposed to explain this observed performance. To suppress the negative effects of surface defect states and atmospheric molecules, new InAs NW photodetectors with a half-wrapped top-gate had been fabricated by using 10 nm HfO2 as the top-gate dielectric.

The use of electricity generated from clean and renewable sources, such as water, wind, or sunlight, requires efficiently distributed electrical energy storage by high-power and high-energy secondary batteries using abundant, low-cost materials in sustainable processes. American Science Policy Reports state that the next-generation “beyond-lithium” battery chemistry is one feasible solution for such goals. Here we discover new “multivalent ion” battery chemistry beyond lithium battery chemistry. Through theoretic calculation and experiment confirmation, stable thermodynamics and fast kinetics are presented during the storage of multivalent ions (Ni2+, Zn2+, Mg2+, Ca2+, Ba2+, or La3+ ions) in alpha type manganese dioxide. Apart from zinc ion battery, we further use multivalent Ni2+ ion to invent another rechargeable battery, named as nickel ion battery for the first time. The nickel ion battery generally uses an alpha type manganese dioxide cathode, an electrolyte containing Ni2+ ions, and Ni anode. The nickel ion battery delivers a high energy density (340 Wh kg−1, close to lithium ion batteries), fast charge ability (1 minute), and long cycle life (over 2200 times).

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Structural hierarchy can enhance the mechanical behavior of materials and systems. This is exemplified by the fracture toughness of nacre or enamel in nature and by human-made architected microscale network structures. Nanoscale structuring promises further strengthening, yet macroscopic bodies built this way contain an immense number of struts, calling for scalable preparation schemes. In this work, we demonstrated macroscopic hierarchical network nanomaterials made by the self-organization processes of dealloying. Their hierarchical architecture affords enhanced strength and stiffness at a given solid fraction, and it enables reduced solid fractions by dealloying. Scaling laws for the mechanics and atomistic simulation support the observations. Because they expose the systematic benefits of hierarchical structuring in nanoscale network structures, our materials may serve as prototypes for future lightweight structural materials.

Flexible asymmetric supercapacitors with excellent electrochemical performance and aesthetic property are realized by using ultrathin two-dimensional (2D) MnO2 and graphene nanosheets as cathode and anode materials, respectively. 2D MnO2 nanosheets (MSs) with a thickness of ca. 2 nm are synthesized with a soft template method for the first time, which achieve a high specific capacitance of 774 F g−1 even after 10000 cycles. Asymmetric supercapacitors based on ultrathin MSs and graphene exhibit a very high energy density up to 97.2 Wh kg−1 with no more than 3% capacitance loss after 10000 cycles in aqueous electrolyte. Most interestingly, we show that the energy storage device can have an aesthetic property. For instance, a “Chinese panda” supercapacitor is capable of lighting up a red light emitting diode. This work has another, quite different aspect that a supercapacitor is no longer a cold industry product, but could have the meaning of art.

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In recent years, it has been an attractive challenge to fabricate multiple stimuli-responsive hybrid microgels composed of polymer microgel and gold nanoparticle (AuNP). Herein, we report on the detailed synthesis of poly(N-isopropylacrylamide-co-methacrylic acid)--Au hybrid microgels by in situ reduction of gold precursor in the presence of thiol-functionalized poly(N-isopropylacrylamide-co-methacrylic acid) microgels. The as-synthesized hybrid microgels showed well-defined swelling/deswelling transition in response to the surrounding temperature, pH, and light irradiation. The hybrid microgels had a unique microstructure where a large number of AuNP's distribute mainly in the interior of microgel with a fluff-like surface. The plasmonic property of the hybrid microgels can be modulated through the volume phase transition induced by the external triggers such as temperature and pH. In the reduction of 4-nitrophenol catalyzed by the hybrid microgels, it was found that the reaction rate did not increase monotonously with temperature but greatly decreased in a certain temperature range, showing a tunable catalytic activity.

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