Functionalized Fluorescent Nanodiamonds with Millisecond Spin Relaxation Times

Area of Science:

• Materials Science
• Quantum Sensing
• Nanotechnology

Background:

• Fluorescent nanodiamonds (FNDs) with nitrogen-vacancy (NV) defects are vital for biological imaging and nanoscale sensing.
• Surface spin noise on FNDs currently limits measurement precision in biosensing applications.

Purpose of the Study:

• To investigate how chemical surface modifications and core-shell structures affect the T1 relaxation times of FNDs.
• To engineer FND surfaces for improved performance in biosensing and imaging.

Main Methods:

• Surface oxidation and silica coating (Stöber method) of 100 nm FNDs.
• Measurement of T1 relaxation times before and after surface modification.
• FT-IR and NEXAFS spectroscopy to analyze surface functional groups and carbon density.
• Monte Carlo modeling to determine optimal shell thickness for chemical sensitivity.

Main Results:

• Surface oxidation and silica coating dramatically increased T1 relaxation times from 320 ± 9 μs to 1.00 ± 0.06 ms.
• Changes in surface functional groups and sp2 carbon density correlate with enhanced spin relaxation.
• Monte Carlo simulations suggest a 1 nm shell thickness maximizes chemical sensitivity.

Conclusions:

• Engineered FND surfaces can achieve bulk-like T1 relaxation times without complex quantum control.
• These surface engineering strategies are critical for overcoming limitations in FND-based biosensing and imaging.
• The study paves the way for more precise and sensitive nanoscale measurements.