一种微小的海洋生物（硅藻）的三维外壳将可能为人类开发新型电子设备（包括能更快更高效检测污染的气体传感器）奠定了基础。
根据硅藻独特、复杂的三维壳结构，美国乔治亚理工学院理工学院材料与工程学院的研究人员利用一种能将外壳的原始硅（二氧化硅）转化成半导体材料硅的化学过程创造出一种新型的气体传感器。这种被转化的壳仍然保留原先的三维结构和纳米级特征，它还能用作电池电极、化学纯化器等。
研究人员估计自然界中存在大约100000种硅藻，并且每种能够形成具有独特复杂的三维形状的壳，这些外壳的形状有的像圆筒、有的像车轮、扇子、星星等。
Sandhage和他的研究组花了几年的时间来尝试通过将原始硅土转化成更有用的材料来利用这些复杂的形状。他们研究的这些最新结果刊登在3月8日的《自然》杂志上。这项研究得到了美国航空科学研究和美国海洋研究办公室的资助。
硅藻是一类种类繁多的低等植物，约11000多种。在海洋中硅藻的种类最多，淡水和潮湿的土壤也不少。据估测每一立方厘米土壤中有羽纹藻约1亿个。硅藻种间个体差异大，小者3.5微米，大者300-600微米。硅藻的身体虽然只有一个细胞，可这一个细胞却非常有趣。它既不象动物细胞一样没有细胞壁，也与植物细胞的细胞壁大不相同。硅藻的细胞壁由大量的硅质组成，分为上下两部分组成，上面的盖叫上壳，下面的底叫下壳，上壳套住下壳，并且上下壳面上纹饰图案非常精美。
部分英文原文：
Nature 446, 172-175 (8 March 2007) | doi:10.1038/nature05570; Received 13 November 2006; Accepted 2 January 2007
Chemical reduction of three-dimensional silica micro-assemblies into microporous silicon replicas
Zhihao Bao1, Michael R. Weatherspoon1, Samuel Shian1, Ye Cai1, Phillip D. Graham1, Shawn M. Allan1, Gul Ahmad1, Matthew B. Dickerson1, Benjamin C. Church1, Zhitao Kang1, Harry W. Abernathy III1, Christopher J. Summers1, Meilin Liu1 and Kenneth H. Sandhage1
School of Materials Science & Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
Correspondence to: Kenneth H. Sandhage1 Correspondence and requests for materials should be addressed to K.H.S. (Email: ken.sandhage@mse.gatech.edu).
The carbothermal reduction of silica into silicon requires the use of temperatures well above the silicon melting point (2,000 °C)1. Solid silicon has recently been generated directly from silica at much lower temperatures (850 °C) via electrochemical reduction in molten salts2, 3. However, the silicon products of such electrochemical reduction did not retain the microscale morphology of the starting silica reactants2, 3. 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 Å). 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 biological4, 5, 6 or synthetic silica templates7, 8, 9 for sensor, electronic, optical or biomedical applications10, 11, 12, 13.
