一種微小的海洋生物（硅藻）的三維外殼將可能為人類開發(fā)新型電子設(shè)備（包括能更快更高效檢測污染的氣體傳感器）奠定了基礎(chǔ),。
根據(jù)硅藻獨特,、復(fù)雜的三維殼結(jié)構(gòu),，美國喬治亞理工學(xué)院理工學(xué)院材料與工程學(xué)院的研究人員利用一種能將外殼的原始硅（二氧化硅）轉(zhuǎn)化成半導(dǎo)體材料硅的化學(xué)過程創(chuàng)造出一種新型的氣體傳感器。這種被轉(zhuǎn)化的殼仍然保留原先的三維結(jié)構(gòu)和納米級特征,，它還能用作電池電極,、化學(xué)純化器等。
研究人員估計自然界中存在大約100000種硅藻,，并且每種能夠形成具有獨特復(fù)雜的三維形狀的殼,，這些外殼的形狀有的像圓筒、有的像車輪,、扇子,、星星等。
Sandhage和他的研究組花了幾年的時間來嘗試通過將原始硅土轉(zhuǎn)化成更有用的材料來利用這些復(fù)雜的形狀,。他們研究的這些最新結(jié)果刊登在3月8日的《自然》雜志上,。這項研究得到了美國航空科學(xué)研究和美國海洋研究辦公室的資助。
硅藻是一類種類繁多的低等植物,，約11000多種,。在海洋中硅藻的種類最多，淡水和潮濕的土壤也不少,。據(jù)估測每一立方厘米土壤中有羽紋藻約1億個,。硅藻種間個體差異大，小者3.5微米,，大者300-600微米,。硅藻的身體雖然只有一個細胞，可這一個細胞卻非常有趣,。它既不象動物細胞一樣沒有細胞壁,，也與植物細胞的細胞壁大不相同。硅藻的細胞壁由大量的硅質(zhì)組成,，分為上下兩部分組成,，上面的蓋叫上殼，下面的底叫下殼,，上殼套住下殼,，并且上下殼面上紋飾圖案非常精美。
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: [email protected]).
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.
