Observing the Surface Termination of LaScO₃ Perovskite Using Solid-State Nuclear Magnetic Resonance

Materials with well-defined surfaces are drawing increased attention for the design of bespoke catalysts and nanomaterials. Gaining a detailed understanding of the surfaces of these materials is an important challenge, which is often complicated by surface polymorphism and dynamic restructuring. We introduce the use of surface-enhanced NMR spectroscopy for the observation of such surfaces, focusing on LaScO₃ as an example. We show that double-resonance NMR experiments correlating surface oxygen and probe molecules to the ¹³⁹La and ⁴⁵Sc nuclei at the surface reveal the material to be terminated by a ScO monolayer. Surface-selective ¹⁷O and ⁴⁵Sc NMR experiments further showed the material to be hydroxyl terminated and that the surface may be prone to dynamic restructuring as a result of moisture exposure. Perhaps most interestingly, surface-selective ¹³⁹La NMR experiments revealed the existence of previously undetected surface lanthanum defects, suggesting that surface-enhanced NMR may be useful as a guide in the synthesis of defect-free surfaces in the design of various nanomaterials.