Silicon nanotube

Si nanotube (top) created by partial etching of Si-covered ZnO nanowire (bottom).^[1]

Si nanotubes created by etching of Si-covered ZnO nanowires.^[1]

Silicon nanotubes are nanoparticles which create a tube-like structure from silicon atoms. They are technologically important because bulk silicon is the key material in the semiconductor industry.^[2] First reports on silicon nanotubes appeared around the year 2000.^[3]

Synthesis

One method to prepare silicon nanotubes is using a reactor employing an electric arc without the use of any catalyst.^[4] To ensure purity, the reactor is evacuated and filled with the nonreactive noble gas argon. The actual formation of the nanotubes relies on the process of chemical vapor deposition.^[5]

A more common laboratory-scale method involves using germanium or zinc oxide nanowires as a template. Silicon, coming typically from either silane or silicon tetrachloride gas, is then deposited onto the nanowires, and the core is dissolved leaving behind a silicon tube.^[6] The growth of template nanowires, silicon deposition and nanowire etching, and consequently the geometry of resulting Si nanotubes, can be accurately controlled in the second method; however, the smallest inner diameter is limited by tens of nanometers.^[1]

Applications

Silicon nanotubes have been considered for use in electronics, because it appears that silicon nanomaterials may behave like a metal fuel, since the structure can accommodate molecules of hydrogen so it might resemble coal without the CO₂.^[7][8] A silicon nanotube charged with hydrogen delivers energy and in the process leaves residual water, ethanol, silicon and sand. However, as hydrogen production requires considerable energy, this is only a proposed method of storing energy, not producing it.

Silicon nanotubes may be used in lithium-ion batteries. Conventional Li-Ion batteries use graphitic carbon as the anode, but replacing this with silicon nanotubes experimentally increases the specific (by mass) anode capacity by a factor of 10 (though the overall capacity improvement is lower due to the far lower specific cathode capacities).^[9]

References

1. Huang, Xuezhen; Gonzalez-Rodriguez, Roberto; Rich, Ryan; Gryczynski, Zygmunt; Coffer, Jeffery L. (2013). "Fabrication and size dependent properties of porous silicon nanotube arrays". Chemical Communications 49 (51): 5760. doi:10.1039/C3CC41913D. PMID 23695426.
2. Mu, C.; Zhao, Q.; Xu, D.; Zhuang, Q.; Shao, Y. (2007). "Silicon Nanotube Array/Gold Electrode for Direct Electrochemistry of Cytochrome c". Journal of Physical Chemistry B 111 (6): 1491. doi:10.1021/jp0657944.
3. Kiricsi, Imre; Fudala, Ágnes; Kónya, Zoltán; Hernádi, Klára; Lentz, Patrick; Nagy, János B (2000). "The advantages of ozone treatment in the preparation of tubular silica structures". Applied Catalysis A: General 203: L1. doi:10.1016/S0926-860X(00)00563-9.
4. De Crescenzi, M.; Castrucci, P.; Scarselli, M.; Diociaiuti, M.; Chaudhari, P. S.; Balasubramanian, C.; Bhave, T. M.; Bhoraskar, S. V. (2005). "Experimental imaging of silicon nanotubes". Applied Physics Letters 86 (23): 231901. doi:10.1063/1.1943497.
5. Sha, J.; Niu, J.; Ma, X.; Xu, J.; Zhang, X.; Yang, Q.; Yang, D. (2002). "Silicon Nanotubes". Advanced Materials 14 (17): 1219. doi:10.1002/1521-4095(20020903)14:17<1219::AID-ADMA1219>3.0.CO;2-T.
6. Moshit, Ishai; Patolsky, Fernando (2009). "Shape- and Dimension-Controlled Single-Crystalline Silicon and SiGe Nanotubes: Toward Nanofluidic FET Devices". Journal of the American Chemical Society 131 (10): 3679–3689. doi:10.1021/ja808483t.
7. Xiao Cheng Zeng; Hideki Tanaka. "Scientists Model Silicon Nanotubes That Appear to Be Metal (AzO Nanotechnology)".
8. Earl Bardsley. "The sand option: Energy from silicon" (PDF).
9. McDermott, Mat. (2009-09-23) Li-Ion Battery Breakthrough: Silicon Nanotubes Boost Capacity 10x. TreeHugger. Retrieved on 2015-11-13.

External links

• Lyon Science Transfer - Université de Lyon, France
• Thin Films of Silicon Nanoparticles Roll into Flexible Nanotubes, University of Illinois