Graphical Non-planar platelets of gold nanocrystals with the lotus leaf- and donut-like morphologies are selectively prepared via seeded growth. The preferable deposition of Au on the central region of plate-like Au seeds is realized by the underpotential-deposition (UPD) effect of Ag ions, while epitaxial growth on the edge part and cold-welding of the newly-formed branches lead to formation of an in-plane hole when Ag + is absent. We report a seeded growth of gold (Au) nanoplates with two distinct morphologies, which are similar to a lotus leaf and a donut, respectively. The success of this synthesis relies on the use of flat Au nanoplates in high purity as seeds, followed by a controlled deposition. In particular, the presence of Ag + led to the deposition of Au atoms preferentially occurred at the central part of one face of the nanoplate and thus the formation of lotus leaf-like shape. In contrast, when Ag + was absent, the growth mainly occurred to the edge region. Then, cold-welding of newly-formed branches and further diffusion of Au atoms created holes in the nanoplate, resulting in the formation of donut-like shape. The Au nano-lotus leaves with tunable sizes exhibited absorbance in near-infrared region and enhanced chemical activities in electrochemical measurements. The current strategy is extended to fabricate Au−Ag nanoplates with a similar lotus leaf-like morphology, which also exhibited strong absorbance in near-infrared region in UV-vis extinction spectra. The current work allows the fabrication of two-dimensional Au-based nanomaterials with concave shape and three-dimensional architecture and could be potentially extended to other noble metals and alloys.
Wang Cunying,Li Congcong,Ge Fuxiang,Tian Wei,Wu Mian,Xiaobing Li
Among numerous oil-water separation materials, coalescence materials have received widespread attention. In this work, we prepared a lotus leaf-shaped Janus coalescing material by physically mixing polyethylene (PE) and polypropylene (PP) first, pressing it into sheets, then single-face hydrophilic modifying by chemical oxidation method, followed by pressing into a lotus leaf shape. Finally, holes were physically punched at the upper and lower sides of the coalescing material to let the oil drops pass through freely, greatly reducing the time for oil droplets to float. The shape of lotus leaves could provide more opportunities for oil droplets to collide and coalesce. The coalescing materials had asymmetric wettability, with specific surfaces that were oleophilic on the one hand and hydrophilic on the other. The oil droplets adhered to the oleophilic side of the coalescing material, coalesced and grew, then floated up and passed through the coalescing sheet layer by layer until they reached the oil collecting port to realize oil-water separation. The structural parameters of the coalescing material were progressively optimized. The obtained coalescing material exhibited a high oil-water separation efficiency of 99.40 ± 0.5% with good stability during a 48 h continuous oil-water separation, which provided a reference for the development of efficient coalescing materials.
Dopamine modified γ -polyglutamic acid ( γ -PGA-DA) copolymer and melamine (Mel) can self-assemble into Mel/ γ -PGA-DA micelles via weak intermolecular interactions in aqueous solution containing small amount of methanol. When Mel/ γ -PGA-DA micellar solution was cast on the surface of formvar stabilized with carbon support films, the lotus-like nano-architectures were formed on the surface of substrate via hierarchical assembly of micelles. The size of lotus-like nanoarchitectures was approximately 200 nm×500 nm. The possible driving forces for hierarchical assembly of micelles were the solution fluid and interaction between micelles. The hierarchical assembly of micelles was similar to the fractal aggregation of inorganic particles and a possible reason was discussed.
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