Alanine Adsorption and Thermal Condensation at the Interface of Fumed Silica Nanoparticles: A Solid-State NMR Investigation

详细信息    查看全文

• 作者：Chengchen Guo ; Gregory P. Holland
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：November 12, 2015
• 年：2015
• 卷：119
• 期：45
• 页码：25663-25672
• 全文大小：584K
• ISSN：1932-7455

文摘

Investigating the interface between biomolecules and nanoparticles has attracted considerable attention in recent years since it has great significance in numerous fields including nanotechnology, biomineralization, cancer therapy, and origin of life. In this paper, we present a thorough solid-state NMR study on alanine adsorption and thermal condensation on fumed silica nanoparticles. The structure and dynamics at the interface between alanine and fumed silica nanoparticles were probed with a combination of ¹H, ¹³C, and ¹⁵N one- and two-dimensional (2D) magic angle spinning (MAS) solid-state NMR methods at different alanine surface coverages and hydration levels. It is illustrated at high surface coverages both crystalline and adsorbed states of alanine exist in the samples while only adsorbed alanine is observed at low surface coverage (approximately a monolayer). At high hydration levels, the adsorbed alanine exhibits enhanced mobility, and both the carboxyl and amine group interact with mobile water molecules on the silica nanoparticle surface. At low hydration levels, the adsorbed alanine interacts with surface silanols via the protonated amine group and the carboxylate group. The thermal condensation of alanine on fumed silica nanoparticles was also investigated, and the results indicate that alanine can undergo thermal condensation at 鈭?70 掳C at the interface of fumed silica nanoparticles as confirmed by a battery of ¹³C and ¹⁵N 2D MAS solid-state NMR experiments. By combining the adsorption and thermal condensation results, a possible mechanism for the silica surface-catalyzed thermal condensation reaction of alanine is proposed.