Single-Nitrogen-Vacancy NMR of Amine-Functionalized Diamond Surfaces

Area of Science:

• Nanoscale science and technology
• Quantum sensing
• Surface chemistry

Background:

• Nuclear magnetic resonance (NMR) imaging using shallow nitrogen-vacancy (NV) centers in diamond shows promise for nanoscale chemical characterization.
• Near-surface NV centers suffer from reduced coherence time and stability, necessitating improved surface termination strategies.
• Current methods lack robust control over adsorbed molecule density, orientation, and binding configuration.

Purpose of the Study:

• To develop a diamond surface preparation that enhances NV center coherence times and enables controlled chemical functionalization.
• To demonstrate nanoscale NMR sensing of single molecules using functionalized NV centers.

Main Methods:

• A novel diamond surface preparation with mixed nitrogen- and oxygen-termination was developed.
• Single NV centers in nanopillar waveguides were utilized for probing.
• Amine-reactive cross-linking was employed for direct and recyclable chemical functionalization.
• ¹⁹F NMR sensing was performed on covalently bound fluorinated molecules.

Main Results:

• The mixed nitrogen- and oxygen-terminated surface improved coherence times for NV centers shallower than 10 nm.
• The surface preparation allowed for direct and recyclable chemical functionalization.
• Detection of approximately 100 molecules was achieved using ¹⁹F NMR sensing with single NV centers.

Conclusions:

• This study presents a significant advancement in diamond surface preparation for nanoscale NMR.
• The developed method enables controlled functionalization and enhances NV center performance for sensitive molecular detection.
• This work paves the way for single-molecule level nuclear spin localization and structure interrogation.