Silica Nanoparticles Three Dimensional Assembly: An Integrative Chemistry Approach Toward Designing Opal-Like Silica Foa
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Silica Nanoparticles Three Dimensional Assembly: An Integrative Chemistry Approach Toward Designing Opal-Like Silica Foams Florent CARN, and Renal BACKOV C.R.P.P. CNRS UPR 8641, 115 Ave. Albert Schweitzer, Pessac, F-33600, France ABSTRACT Novel meso-/macroporous SiO2 monoliths have been reached by applying a nanotectonic pathway within a confined geometry, i.e. a non-static air-liquid foam pattering process. Final scaffolds are a very close transcription of the tailored periodic air-liquid foam template while close-packed silica colloids are texturing the as-synthesized foam walls. The interconnected nanoparticles and associated void space between adjacent particles allow generating intrinsic mesopores, thereby defining hierarchically organized porous scaffolds. The good control over both the air-liquid foam’s water volume fraction and the bubble size allow a rational tuning of the macropore shape (diameter, Plateau border’s width). At the nano-scale, heterogeneous textural character is associated with abrupt variation in the film’s topology certainly governed by the complex liquid flow present within the foam film. This flow induces a surfactant concentration gradient that causes a sort of marginal regeneration on the side of the film. According to these observations, the heterogeneous character of the film surface revealed by AFM can be interpreted like a direct expression of the liquid flow within the air-liquid foam’s film.
INTRODUCTION The synthesis of micro- and / or meso-porous inorganic materials is a very competitive and quite mature research area regarding the wide range of strategies proposed in the literature [1,2]. Beyond those meso- and/or nanoscopic concerns, the properties of final porous materials are also strongly related on the way of the solid is textured at the macroscopic length scale [3]. In this specific issue of high scale organization, shaping macroscopic monolith in the form of highly open-cell macroporous network with well defined topology, morphology and cell dimension appears as an important task to reach that strongly influences the suitability toward potential applications as thermal and/or acoustic insulation [3], tissue engineering [4] or heterogeneous catalysis [5]. Considering this general context, materials with higher order architecture can be prepared by different route involving self-assembly [6], shape directed assembly [7] even layer by layer assembly [8] when considering bidimensional systems. A promising approach to engineer hierarchically organized materials with macropore diameter ranging from 5 µm up to 600 µm involves the use of complex fluid such like biliquid [9-11] or air-liquid foam [12-16]. However, the rational control of the macropore architecture (i.e. dimension and morphology) and connectivity (i.e. topologic aspect), associated with an enhanced structural stability toward moisture, thermal treatment and compression remains an experimental challenge. In the present study we propose a new synthesizing route by achieving the very close transcripti
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