Dehydration, Dehydroxylation, and Rehydroxylation of Single-Walled Aluminosilicate Nanotubes

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• 作者：Dun-Yen Kang ; Ji Zang ; Elizabeth R. Wright ; Arthur L. McCanna ; Christopher W. Jones ; Sankar Nair
• 刊名：ACS Nano
• 出版年：2010
• 出版时间：August 24, 2010
• 年：2010
• 卷：4
• 期：8
• 页码：4897-4907
• 全文大小：742K
• 年卷期：0
• ISSN：1936-086X

文摘

Single-walled metal oxide (aluminosilicate) nanotubes are excellent candidates for addressing the long-standing issue of functionalizing nanotube interiors, due to their high surface reactivity and controllable dimensions. However, functionalization of the nanotube interior is impeded by its high surface silanol density (9.1 −OH/nm²) and resulting hydrophilicity. Controlled dehydration of the nanotubes is critical for the success of functionalization efforts. We employ a range of solid-state characterization tools to elucidate dehydration and dehydroxylation phenomena in the nanotubes as a function of heat treatment up to 450 °C. Vibrational spectroscopy (Fourier transform infrared, FT-IR), thermogravimetric analysis-mass spectrometry (TGA-MS), nitrogen physisorption, solid-state NMR, and X-ray diffraction (XRD) reveal that a completely dehydrated condition is achieved at 250 °C under vacuum and that the maximum pore volume is achieved at 300 °C under vacuum due to partial dehydroxylation of the dehydrated nanotube. Beyond 300 °C, further dehydroxylation partially disorders the nanotube wall structure. However, a unique rehydroxylation mechanism can partially reverse these structural changes upon re-exposure to water vapor. Finally, detailed XRD simulations and experiments allow further insight into the nanotube packing, the dimensions, and the dependence of nanotube XRD patterns on the water content.