Method for real-time monitoring of paramagnetic reactions using spin relaxometry with fluorescent nanodiamonds

TL;DR

This paper introduces a rapid, cost-effective method for real-time monitoring of paramagnetic reactions using spin relaxometry with fluorescent nanodiamonds, significantly improving speed over traditional techniques.

Contribution

The authors developed an optimized cuvette-based system with FPGA integration for fast T1 relaxometry, enabling real-time chemical reaction monitoring with high sensitivity.

Findings

Achieved over 15-second detection of Cu ion reduction

Speed increased by over two orders of magnitude compared to traditional methods

Reduced cost of T1 relaxometry measurements by an order of magnitude

Abstract

Spin relaxometry using fluorescent nanodiamonds (FNDs) has been applied successfully to sense numerous paramagnetic target molecules such as free radicals and metalloproteins. However, despite their high sensitivity, T1 spin relaxation measurements are often hampered by their slow acquisition speed. Here, we demonstrate a method that allows for real-time monitoring of paramagnetic chemical reactions. We demonstrate T1 spin relaxometry from thousands of FNDs using an optimised cuvette-based system integrating an avalanche photodiode operated in linear mode, and a fast, fieldprogrammable gate array (FPGA) for data collation. We demonstrate chemical monitoring of the reduction of Cu(II) to Cu(I) ions in-solution with a 15 second integration using an optimised T1 sensing protocol. Our method achieves more than two orders of magnitude speed up with an order of magnitude reduction in cost when compared with traditional techniques. With further technical improvements, we believe this in-solution method could be extended to sense the sub-second chemical kinetics of paramagnetic molecules in solution.