Unraveling the Core–Shell Structure of Ligand-Capped Sn/SnOx Nanoparticles by Surface-Enhanced Nuclear Magnetic Resonance, Mössbauer, and X-ray Absorption Spectroscopies

摘要: A particularly difficult challenge in the chemistry of nanomaterials is detailed structural and chemical analysis multicomponent nano-objects. This especially true for determination spatially resolved information. In this study, we demonstrate that dynamic nuclear polarization surface-enhanced solid-state NMR spectroscopy (DNP-SENS), which provides selective enhanced signal collection from (near) surface regions a sample, can be used to resolve core-shell structure nanoparticle. Li-ion anode materials, monodisperse 10-20 nm large tin nanoparticles covered with ∼3 thick layer native oxides, were case study. DNP-SENS selectively weak 119Sn amorphous SnO2 layer. Mossbauer X-ray absorption spectroscopies identified subsurface SnO phase quantified atomic fractions both oxides. Finally, temperature-dependent diffraction measurements probe metallic β-Sn core indicated even after 8 months storage at 255 K there are no signs conversion into brittle semiconducting α-phase, transition normally occurs bulk 286 (13 °C). Taken together, these results indicate Sn/SnOx have core/shell1/shell2 Sn/SnO/SnO2 phases. The study suggests experiments carried on many types uniform colloidal containing NMR-active nuclei, presence either hydrophilic (ion-capped surfaces) or hydrophobic (capping ligands long hydrocarbon chains) functionalities.