Understanding St枚ber Silica鈥檚 Pore Characteristics Measured by Gas Adsorption

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• 作者：Shanshan Li ; Quan Wan ; Zonghua Qin ; Yuhong Fu ; Yuantao Gu
• 刊名：Langmuir
• 出版年：2015
• 出版时间：January 20, 2015
• 年：2015
• 卷：31
• 期：2
• 页码：824-832
• 全文大小：394K
• ISSN：1520-5827

文摘

Controversial reports regarding St枚ber silica鈥檚 microporosity and specific surface area remain in the literature despite decades of widespread applications. In this work, St枚ber silica samples prepared under controlled reaction time and postsynthesis washing/drying conditions were characterized by nitrogen adsorption at 77 K, transmission electron microscopy, elemental analysis, Fourier transform infrared spectroscopy, thermal analysis, and evolved gas analysis. Our experimental results demonstrated the important but often overlooked effects of reaction time and postsynthesis treatments on St枚ber silica鈥檚 pore characteristics, as evidenced by the strikingly large range of BET specific surface area (11.3鈥?09.7 m²/g). A simple micropore filling and blocking mechanism compatible with an existing St枚ber silica growth model incorporating both aggregation and monomer addition steps was proposed to explain all our experimental findings. The carbon and nitrogen contents appear to serve well as the indicative link between our experimental variables and the resulting pore blocking by TEOS and its derivatives. A suitable combination of experimental conditions is recommended in order to make microporous St枚ber silica samples with large specific surface area, including a short reaction time, water washing, and drying at moderate temperature preferably under vacuum.