A combined top-down and bottom-up approach to fabricate silica films with bimodal porosity

Ijichi, Kazuya; Fukuoka, Ayumu; Shimojima, Atsushi; Sugiyama, Masakazu; Okubo, Tatsuya

doi:10.1016/j.matlet.2010.11.064

Cited by 8 publications

(3 citation statements)

References 25 publications

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“…Preparation of mesoporous films is an active research area. 412 Mesoporous silica films can be prepared by two different methods. First, a hydrothermal deposition process based on heterogeneous nucleation and growth of mesostructured silica seeds can be used.…”

Section: Films Of Mesoporous Structures 411 Mesoporous Silica Filmsmentioning

confidence: 99%

Nanoarchitectonics for Mesoporous Materials

Ariga

Vinu

Yamauchi

et al. 2011

Bulletin of the Chemical Society of Japan

716

411

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Although mesoporous materials have well-defined pore structures, these fine materials can surprisingly be produced by employing a set of conventional and simple procedures such as mixing, heating, filtration, and washing, using low-cost materials. They can be regarded as easy-to-make bulk nanostructured materials. Mesoporous materials have great potential for use in both macroscopic applications and nanotechnology. In this account, we introduce examples of recent developments in mesoporous materials involving innovations in their components and structural designs and concentrating on our own recent progress. These examples include syntheses of mesoporous silica, metal oxides, semiconductive materials, metals, alloys, organic composites, biomaterial composites, carbon, carbon nitride, and boron nitride, as innovative components. As structural innovations for mesoporous materials, various film preparations, pore alignments, and hierarchic structures are described together with their related functions including sensing and controlled release of target molecules. Why Mesoporous Materials? Bulk Quantities and Precise StructuresThere is little doubt that nanotechnology and related technologies are making significant contributions to current research and development which will eventually be felt in our day-to-day lives. Device miniaturization in such products as cellular phones and portable computers has irrevocably changed our lifestyles. Portable devices allow us to work and communicate wherever we are in the world in contrast to the previous situation where machine operation required a human presence. Greater freedom in our work and leisure dispositions should diminish over-concentration of populations in cities and may ultimately reduce energy consumption and waste production.So far, device innovations have been due to development of top-down approaches, especially sophisticated microfabrication techniques. 17 However, those top-down techniques are not useful for materials innovation where chemical processes are used as the operating principle. Rather, so-called bottom-up approaches are expected to create novel functional materials having well-controlled structural features with nanometric precision. Bottom-up approaches rely on self-assembly processes to form selected structures through spontaneous association of atoms, molecules, clusters, and particles. 818 Furthermore, assisted assembly techniques using external influences are provided by LangmuirBlodgett (LB) method 1928 and layer-by-layer (LbL) adsorption 2936 and provide significant contributions for materials' fabrication. According to these concepts, molecular complex formation, 3741 molecular array control, 4252 and microscopic structural design 5361 have been widely investigated leading to generation of a large quantity of scientific knowledge.Ideally, materials should be produced in a series of easy processes to yield bulk quantity without loss of nanometric structural features and some categories of material already satisfy this condition. For exampl...

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Section: Films Of Mesoporous Structures 411 Mesoporous Silica Filmsmentioning

confidence: 99%

Nanoarchitectonics for Mesoporous Materials

Ariga

Vinu

Yamauchi

et al. 2011

Bulletin of the Chemical Society of Japan

716

411

View full text Add to dashboard Cite

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“…There are currently four reports ,− on the direct surface observations of the structures of the outermost surfaces of mesoporous silica thin films prepared by EISA, in addition to two studies referenced above. In these studies, atomic force microscopy (AFM), SEM, AFM and SEM, or AFM combined with X-ray reflectivity (XRR) measurements were used for determining the nature of the outermost surfaces. In these studies, SEM images were taken at relative high voltage (a few kV) with and without metal sputtering on the surfaces of the specimen.…”

Section: Introductionmentioning

confidence: 99%

“…In these studies, atomic force microscopy (AFM), SEM, AFM and SEM, or AFM combined with X-ray reflectivity (XRR) measurements were used for determining the nature of the outermost surfaces. In these studies, SEM images were taken at relative high voltage (a few kV) with and without metal sputtering on the surfaces of the specimen. However, AFM results are not so informative in determining whether the periodically structured surfaces can be ascribed to open mesopores, for the following reasons.…”

Section: Introductionmentioning

confidence: 99%

Direct Observation of the Outermost Surfaces of Mesoporous Silica Thin Films by High Resolution Ultralow Voltage Scanning Electron Microscopy

et al. 2017

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The properties of the outermost surfaces of mesoporous silica thin films are critical in determining their functions. Obtaining information on the presence or absence of silica layers on the film surfaces and on the degree of mesopore opening is essential for applications of surface mesopores. In this study, the outermost surfaces of mesoporous silica thin films with 3-dimensional orthorhombic and 2-dimensional hexagonal structures were observed using ultralow voltage high resolution scanning electron microscopy (HR-SEM) with decelerating optics. SEM images of the surfaces before and after etching with NHF were taken at various landing voltages. Comparing the images taken under different conditions indicated that the outermost surfaces of the nonetched mesoporous silica thin films are coated with a thin layer of silica. The images taken at an ultralow landing voltage (i.e., 80 V) showed that the presence or absence of surface silica layers depends on whether the film was etched with an aqueous solution of NHF. The mesostructures of both the etched and nonetched films were visible in images taken at a conventional landing voltage (2 kV); hence, the ultralow landing voltage was more suitable for analyzing the outermost surfaces. The SEM observations provided detailed information about the surfaces of mesoporous silica thin films, such as the degree of pore opening and their homogeneities. AFM images of nonetched 2-dimensional hexagonal mesoporous silica thin films show that the shape of the silica layer on the surface of the films reflects the curvature of the top surface of the cylindrical mesochannels. SEM images taken at various landing voltages are discussed, with respect to the electron penetration range at each voltage. This study increases our understanding of the surfaces of mesoporous silica thin films, which may lead to potential applications utilizing the periodically arranged mesopores on these surfaces.

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