Au nanobipyramids (NBPs) are important nanostructures which attract much attention due to their unique structure, optical, and catalytic properties. The controlled synthesis of Au NBPs and corresponding mechanistic study are highly desirable for both fundamental research and practical applications. Herein, we demonstrate a strategy that large sized Au decahedra with well-defined shape act as seeds for growing NBPs. Furthermore, through using different sized decahedra seeds with edge from 25 to 49 nm, various sized NBPs can be easily prepared (longitudinal length from 110 to 210 nm; transverse length from 36 to 70 nm). Our study provides hard evidence for the growth of NBPs that they surely stem from the overgrowth on penta-twinned decahedra. Because these used large size seeds have well-defined shape and structure, the growth of the NBPs can be easily determined. Results show that the formation of NBPs is primarily determined by the molar ratio of Au(3+) and Au seeds (MRAA). MRAA less than 4 only causes size enhancement and no significant shape change. In cases of MRAA higher than 4 and lower than 8, quasi-nanorods are produced. When MRAA range from 8 to 10, NBPs form and the yield is higher than 90%. The effect of reaction time and temperature also are vital to the growth of NBPs. These prepared NBPs are found to exhibit excellent surface enhanced Raman scattering (SERS) performance because of many present hotspots, edges, steps, and tips on their surfaces.

Au nanostructures attract much attention due to their potential applications in many fields. The controlled synthesis is critical to their properties modulation and applications. AgNO3-assisted synthesis is a widely used method for controllably preparing Au nanostructures in aqueous system. Herein, the effect of AgNO3 on the growth of Au nanostructures in polyol is studied. We observe an unusual effect that AgNO3 can induce the formation of pentatwinned Au nanostructures (nanorods and decahedra) and block the growth of Au nanorods. More interestingly, this blocking effect can be tuned through controlling the amount of AgNO3. A moderate amount of AgNO3 facilitates the formation of Au nanorods. A large amount of AgNO3 completely blocks the growth of nanorods and favors the formation of high quality decahedra (decahedra can be considered as nanorods with 0 nm longitudinal length). Besides, this blocking effect also allows preparation of different high-index-faceted Au nanobipyramids. These prepared Au nanostructures further serve as starting templates to fabricate other heterostructured Au/Ag nanomaterials, such as Ag-Au-Ag segmental nanorods, Au@Ag core-shelled nanostructures. The prepared nanostructures exhibit size- and structure-dependent catalytic performance in the reduction of p-nitrophenol to p-aminophenol by sodium borohydride.

We present a general route for synthesizing M@ZnO nanoparticles (NPs) by using ascorbic acid (AA) to induce deposition of ZnO on various shaped and structured cationic-surfactant-capped NP surfaces (noble, magnetic, semiconductor, rod-like, spherical, cubic, dendrite, alloy, core@shell). The results show that the complexing (AA and Zn(2+)) and cooperative effects (AA and CTAB) play important roles in the formation of polycrystalline ZnO shells. Besides, the growth kinetics of M@ZnO was systematically studied. It was found that the slow growth rate favors the successful formation of uniform core@ZnO NPs with relatively loose shells. An appropriate growth rate allows achieving high quality M@ZnO NPs with dense shells. However, very fast growth causes significant additional nucleation and the formation of pure ZnO NPs. This general method is suitable for preparing M@ZnO using seed NPs prepared in both water and organic phases. It might be an alternative route for functionalizing NPs for bioapplications (ZnO is biocompatible), modulating material properties as designed, or synthesizing template materials for building other nanostructures.

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Using the Gemini surfactant [C12H25N+(CH3)2-(CH2)2-N+(CH3)2-C12H25]·2Br- (abbreviated as C12-2 - 12) with the short spacer group (s = 2) as structure-directing agent and sodium silicate as precursor, high-quality ordered cubic mesoporous silica (space group Ia3d) was prepared through the S+I- route (S denotes surfactant, I precursor). The samples were characterized by small-angle X-ray diffraction, transmission electron microscopy, and N2 adsorption−desorption techniques. Results showed that the pore structure of the resulting mesoporous silica belonged to the cubic structure (space group Ia3d). The high-quality cubic mesoporous structure was formed at 1:0.33 (molar ratio of sodium silicate to C12-2 - 12), 2:1 (ethyl acetate to sodium silicate), and at 30 °C. The formation conditions of MCM-48 with C12-2 - 12 were milder than those with the corresponding monovalent surfactants, such as alkyltrimethylammonium bromide. N2 adsorption−desorption curves revealed type IV isotherms and H1 hysteresis loops; Brunauer−Emmet−Teller (BET) surface areas increased with the decrease of the molar ratio of sodium silicate to C12-2 - 12 and of ethyl acetate to sodium silicate as well as of the hydrothermal temperatures.

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Supercritical CO2 as a blowing agent has attracted increasing interest in the preparation of microcellular polyamide 6 (PA6) foams. In this work, we developed the supercritical CO2‐assisted method to prepare a series of different microcellular PA6 foams by controlling its crystallization properties in two steps and carefully investigated the corresponding crystallization properties of modified PA6 and foams using various techniques. Initially, a multifunctional epoxy‐based chain extender (CE) was used to produce high‐melt strength‐modified PA6 with improved foaming ability; then, the resulting PA6 was foamed to prepare the microcellular foams of PA6 using supercritical CO2 as a blowing agent in a batch foaming route. The CE effectively enhanced the melt strength of PA6, and CE usage was optimized to obtain a threshold of high branching without crosslinking. The number of crystals was also adjusted by the saturation temperature. Furthermore, these crystals that formed during the saturation process served as high‐efficiency bubble nucleating agents and then limited the growth of bubbles at the same time. The microcellular foams of PA6 were successfully obtained with a cell size of 10.0 μm, and cell density of 2.0 × 109 cells/cm3 at the saturation temperature of 225°C.