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2625155 
Journal Article 
Method to measure refractive indices of small nonspherical particles: Application to black carbon particles 
Moteki, N; Kondo, Y; Nakamura, SI 
2010 
Yes 
Journal of Aerosol Science
ISSN: 0021-8502
EISSN: 1879-1964 
41 
5 
513-521 
WOS:000277817600009 
We demonstrate a synthetic strategy toward functional, composite porous materials by incorporating functionalized porous silica spheres into a hierarchically porous silica matrix. Monodisperse mesoporous silica spheres decorated with organic probe molecules for visual Cd(2+) ion detection were coated with a thin protecting poly(methyl methacrylate) (PM MA) layer to form core-shell particles. When these particles were redispersed in a mixture of a silica precursor, surfactant and hydrochloric acid, hierarchically structured composite films could be prepared by spin-coating and aging. The PM M A capsule protected the mesoporous silica spheres from being exposed to the silica precursor in the assembly step, which could have blocked the mesopores and/or reacted with the surface functional species. Once the polymer and surfactant components were removed by extraction while preserving the organic probe molecules within the silica spheres, composite porous structures were derived in which the mesoporous silica spheres were surrounded by a skeleton of another mesoporous silica phase. An observed color change of the film after exposure to analyte solutions with low concentrations of Cd(2+) ions confirmed that the confined probe molecules remained active after the multiple processing steps and that they were accessible via the mesopores in the silica matrix surrounding the embedded spheres. By separating the sphere synthesis and functionalization steps from the film casting step, it is possible to choose different pore-forming surfactants during the syntheses of the spheres and the matrix, and in principle, to embed multiple sets of mesoporous spheres with different functional groups, whose syntheses may not be compatible with each other. 
Aerosol optics; Light scattering; Refractive index; Black carbon