Surface NMR using quantum sensors in diamond

Abstract

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.

Advances in nano- and microscale NMR spectroscopy using diamond quantum sensors

“…By the same token, shallow NV ensembles for NMR spectroscopy have demonstrated their potential in surface sciences, 77 due to the simple setup and robust measurements. Here, we envision a bright future for NV-NMR using NV centers as a novel analytical tool for material, catalysis, and energy research, ideally under in operando conditions.…”

“…A recent study has expanded the aluminum oxide platform for surface NMR demonstrated by Liu et al , 77 including additional binding moieties such as biotin or azides by multiple follow-up functionalization of the Al 2 O 3 support. 100 This approach enables the efficient coupling of biomolecules such as proteins or DNA to the aluminum oxide deposited on the diamond's surface and expands the prospect of surface NV-NMR for biomolecules or biochemistry.…”

“…Interfacial and surface properties are vital for numerous material functions and applications in catalysis, energy conversion, or bioanalytics, especially under chemical-relevant conditions. 77 However, state-of-the-art surface analysis techniques require ultra-high vacuum, intense synchrotron radiation, or femtosecond lasers. Even then, chemical reaction kinetics and molecular dynamics are ultimately challenging to measure under ambient conditions.…”

“…Even then, chemical reaction kinetics and molecular dynamics are ultimately challenging to measure under ambient conditions. Liu et al 77 recently demonstrated the application of NV-NMR in combination with atomic layer deposition (ALD) to study self-assembled monolayers (SAM) under ambient conditions (see Fig. 4a ).…”

Chemical and structural identification of material defects in superconducting quantum circuits

“…Only the latter exploits quantum two-level systems for both magnetic field [132] and electric field [133] sensing. Surface NMR with NV centers in diamond is also emerging as a powerful technique to reveal the chemical information and reaction chemistry of surfaces, and can for example be applied to study hydroxylation of Al 2 O 3 surfaces [134]. NV magnetometry can be performed either in a scanning probe configuration [132] or by addressing individual NV centers close to a coated diamond surface [135].…”