Surface NMR using quantum sensors in diamond

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 119; no. 5
• Main Authors: Liu, Kristina S, Henning, Alex, Heindl, Markus W, Allert, Robin D, Bartl, Johannes D, Sharp, Ian D, Rizzato, Roberto, Bucher, Dominik B
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 01-02-2022
• Subjects: Aluminum; Aluminum oxide; Atomic layer epitaxy; Biological research; Catalysis; Diamonds; Interfaces; Liquid-solid interfaces; Materials science; Monolayers; NMR; Nuclear magnetic resonance; Phosphonates; Physical Sciences; Quantum sensors; Self-assembled monolayers; Self-assembly; Sensitivity analysis; Sensors; Thin films; quantum sensing; surface analysis; spectroscopy; self-assembled monolayer; NV center in diamond
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2111607119

NMR is a noninvasive, molecular-level spectroscopic technique widely used for chemical characterization. However, it lacks the sensitivity to probe the small number of spins at surfaces and interfaces. Here, we use nitrogen vacancy (NV) centers in diamond as quantum sensors to optically detect NMR signals from chemically modified thin films. To demonstrate the method's capabilities, aluminum oxide layers, common supports in catalysis and materials science, are prepared by atomic layer deposition and are subsequently functionalized by phosphonate chemistry to form self-assembled monolayers. The surface NV-NMR technique detects spatially resolved NMR signals from the monolayer, indicates chemical binding, and quantifies molecular coverage. In addition, it can monitor in real time the formation kinetics at the solid-liquid interface. With our approach, we show that NV quantum sensors are a surface-sensitive NMR tool with femtomole sensitivity for in situ analysis in catalysis, materials, and biological research.