Biomimetic method for metallic nanostructured mesoscopic models fabrication
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Biomimetic method for metallic nanostructured mesoscopic models fabrication Gennady V. Strukov and Galina K. Strukova Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, *E-mail: [email protected] ABSTRACT Various metallic structures of complex shape, resembling natural objects such as plants, mushrooms, and seashells, were produced when growing nanowires by means of pulsed current electroplating in porous membranes. These structures occur as the result of nanowires selfassembling (biomimetics) if the electroplating is continued after the nanowires reach the membrane surface. By varying the membrane geometry and the pulsed current parameters, and alternating electroplating from two baths with different electrolytes, various models were fabricated, including a hollow container with wall thickness of 10-30 nm. The possibility of shape regulation for models was demonstrated: in certain conditions, mushroom- and shell-like convex-concave models of the same kind were obtained. The hierarchical structure of models at the nano-, micro- and mesoscopic levels is shown through fragmentation and chemical etching. This biomimetic method suggests an analogy between the shape-forming processes of natural plants and their metallic models. Nanostructured mesoscopic objects of metals (Ag, Pd, Rh, Ni, Bi), alloys (PdNi, PdCo, PbIn) as well as their combinations (PdNi/ Pb, PdNi/ PbIn) were obtained. The technological simplicity of the present method makes it suitable for fabricating nanostructured materials that may be efficient in catalysis, superhydrophobic applications, medical filters, and nanoplasmonics. INTRODUCTION In the process of nanowire growth by electroplating of metal on porous membranes, our attention was attracted by the mesoscopic structures forming on the top of the membrane when the growth was continued after the nanowires reached the membrane surface. The similarity between the obtained structures and natural objects (plants, mushrooms, shells) was striking. Development of bio-inspired methods of fabricating replicas or models of natural objects is a substantial research topic, as some natural materials possess unique properties still unattainable in artificial materials [1]. Superhydrophobicity of the lotus leaf and some other plants, and fracture- toughness of nacre [1,2], are among those useful properties. Recently, researchers' interest has been attracted by “nanoflowers”, anisotropic metal nanostructures. For instance, the effects of giant Raman scattering on gold [3,4] and of catalytic activity on platinum nanoflowers [5,6] have been reported. However, comparison of our results and the data available in the literature provides no information on general methods that enable synthesis and shape control of such “plant” structures. The present work aims is to demonstrate the method of controlled-growth, metallic nanostructured mesoscopic models as well as reveal their architecture and hierarchic structure. A particular issue is to show the feasibility of model shape control, i.e.,
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