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A silica sol–gel design strategy for nanostructured metallic materials

Abstract

Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol–gel process. The porous materials made by silica sol–gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol–gel process built around a multifunctional sol–gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals—including noble metals—to be combined into a library of sol–gel materials with a high degree of control over composition and structure. We demonstrate that the sol–gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S cm−1. This improves the electrical conductivity of porous silica sol–gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices.

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Figure 1: Synthesis of sol–gel precursor and sol–gel-derived thick films.
Figure 2: Structure control in sol–gel hybrids.
Figure 3: Structure analysis of porous pyrolysed palladium nanocomposites.
Figure 4: Electrical transport measurements on porous, pyrolysed, palladium-based films.

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Acknowledgements

The authors acknowledge support of this research by the DOE (DE-FG02-03ER46072) and the NSF through single investigator awards (DMR-0605856 and DMR-1104773). We further acknowledge use of facilities of the Cornell Center for Materials Research (CCMR) with financial support from the Materials Research Science and Engineering Center programme of the National Science Foundation (cooperative agreement DMR 0520404). X-ray diffraction at the Cornell High Energy Synchrotron Source (CHESS) is supported by the National Science Foundation under award DMR-0225180. S.C.W. acknowledges support from the EPA STAR fellowship programme. We thank Debra Rolison for helpful discussions.

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Contributions

S.C.W. designed the sol–gel chemistry and carried out most experiments and data analysis. M.R.P. and S.C.W. synthesized the sol–gel precursors and hybrid films. A.M.A. and S.C.W. synthesized the block-copolymer hybrids. M.K. carried out colloidal crystal templating. E.H. and T.S. synthesized Stöber-type particles. A.A.B. and S.C.W. carried out EDX. S.C.W. carried out electrical conductivity measurements. H.A. etched silica. H.S. and J.W. carried out Raman measurements. Z.L., A.M.A. and S.C.W. prepared and analysed the block-copolymer hybrids. J.S. and S.C.W. synthesized the block copolymers. U.W-Z. and J.W.Z. carried out solid-state NMR measurements. S.C.W. and U.W. wrote the manuscript and all authors contributed to revisions. M.G., F.J.D. and U.W. supervised the research.

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Correspondence to Ulrich Wiesner.

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Warren, S., Perkins, M., Adams, A. et al. A silica sol–gel design strategy for nanostructured metallic materials. Nature Mater 11, 460–467 (2012). https://doi.org/10.1038/nmat3274

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