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Liu, Meilin
Liu Research Group
Research Interests
  • Fuel Cells

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Chemical reduction of three-dimensional silica micro-assemblies into microporous silicon replicas

Cited 271 times inthomson ciCited 233 times inthomson ci
Title
Chemical reduction of three-dimensional silica micro-assemblies into microporous silicon replicas
Author
Bao, ZhihaoWeatherspoon, Michael R.Shian, SamuelCai, YeGraham, Phillip D.Allan, Shawn M.Ahmad, GulDickerson, Matthew B.Church, Benjamin C.Kang, ZhitaoAbernathy, Harry W., IIISummers, Christopher J.Liu, MeilinSandhage, Kenneth H.
Keywords
POROUS SILICON; GAS SENSOR; VAPOR; EMISSION; DIOXIDE; WATER
Issue Date
200703
Publisher
NATURE PUBLISHING GROUP
Citation
NATURE, v.446, no.7132, pp.172 - 175
Abstract
The carbothermal reduction of silica into silicon requires the use of temperatures well above the silicon melting point (≥2,000°C). Solid silicon has recently been generated directly from silica at much lower temperatures (≤850°C) via electrochemical reduction in molten salts. However, the silicon products of such electrochemical reduction did not retain the microscale morphology of the starting silica reactants. Here we demonstrate a low-temperature (650°C) magnesiothermic reduction process for converting three-dimensional nanostructured silica micro-assemblies into microporous nanocrystalline silicon replicas. The intricate nanostructured silica microshells (frustules) of diatoms (unicellular algae) were converted into co-continuous, nanocrystalline mixtures of silicon and magnesia by reaction with magnesium gas. Selective magnesia dissolution then yielded an interconnected network of silicon nanocrystals that retained the starting three-dimensional frustule morphology. The silicon replicas possessed a high specific surface area (>500 m2 g-1), and contained a significant population of micropores (≤20 A). The silicon replicas were photoluminescent, and exhibited rapid changes in impedance upon exposure to gaseous nitric oxide (suggesting a possible application in microscale gas sensing). This process enables the syntheses of microporous nanocrystalline silicon micro-assemblies with multifarious three-dimensional shapes inherited from biological or synthetic silica templates for sensor, electronic, optical or biomedical applications.
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DOI
http://dx.doi.org/10.1038/nature05570
ISSN
0028-0836
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