title: Stacking structure of confined 1-butanol in SBA-15 investigated by solid-state NMR spectroscopy.
abstract: Understanding the complex thermodynamic behavior of confined amphiphilic molecules in biological or mesoporous hosts requires detailed knowledge of the stacking structures. Here, we present detailed solid-state NMR spectroscopic investigations on 1-butanol molecules confined in the hydrophilic mesoporous SBA-15 host. A range of NMR spectroscopic measurements comprising of (1)H spin-lattice (T(1)), spin-spin (T(2)) relaxation, (13)C cross-polarization (CP), and (1)H,(1)H two-dimensional nuclear Overhauser enhancement spectroscopy ((1)H,(1)H 2D NOESY) with the magic angle spinning (MAS) technique as well as static wide-line (2)H NMR spectra have been used to investigate the dynamics and to observe the stacking structure of confined 1-butanol in SBA-15. The results suggest that not only the molecular reorientation but also the exchange motions of confined molecules of 1-butanol are extremely restricted in the confined space of the SBA-15 pores. The dynamics of the confined molecules of 1-butanol imply that the (1)H,(1)H 2D NOESY should be an appropriate technique to observe the stacking structure of confined amphiphilc molecules. This study is the first to observe that a significant part of confined 1-butanol molecules are orientated as tilted bilayered structures on the surface of the host SBA-15 pores in a time-average state by solid-state NMR spectroscopy with the (1)H,(1)H 2D NOESY technique.
authors.affiliation: Nanoelectrochemistry Laboratory, Department of Chemical Engineering, National Taiwan University of Science and Technology, #43, Sec.4, Keelung Rd., Taipei 106, Taiwan.
authors.forename: Yun-Chih
authors.initials: YC
authors.lastname: Lin
authors.forename: Hung-Lung
authors.initials: HL
authors.lastname: Chou
authors.forename: Loka Subramanyam
authors.initials: LS
authors.lastname: Sarma
authors.forename: Bing-Joe
authors.initials: BJ
authors.lastname: Hwang
mesh_terms: D020001:1-Butanol / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D015394:Molecular Structure; D012822:Silicon Dioxide
chemical_list: C509969:SBA-15; D012822:Silicon Dioxide; D020001:1-Butanol