Zero- to low-field J-spectroscopy with a diamond magnetometer

TL;DR

This paper demonstrates the detection of zero- to ultra-low-field NMR signals using a diamond magnetometer, enabling portable, noninvasive chemical analysis at very low frequencies with high sensitivity.

Contribution

It introduces a diamond-based sensor capable of detecting ultra-low-field NMR signals with high sensitivity, advancing portable quantum sensing technology.

Findings

Detected NMR signals at 1.7 Hz and 3.4 Hz using a diamond magnetometer.

Achieved sensor sensitivity of 13 pT/√Hz at frequencies above 5 Hz.

Demonstrated potential for portable, noninvasive chemical diagnostics.

Abstract

We report measurements of zero- to ultra-low-field nuclear magnetic resonance (ZULF NMR) signals at frequencies of a few hertz with a diamond-based magnetic sensor. The sensing diamond is a truncated pyramid with 0.18 mm height and a 0.5 mm x 0.5mm base. The minimum stand-off distance is < 1 mm, and the sensor sensitivity is 13 pT/(Hz)^(1/2) at frequencies f above 5 Hz with 1/f-like behavior at lower frequencies. NMR signals were generated via signal amplification by reversible exchange (SABRE) parahydrogen-based hyperpolarization resulting in zero-field signals at 1.7 Hz and 3.4 Hz corresponding to the expected hetero-nuclear J-coupling pattern of acetonitrile. This work demonstrates a magnet-free platform for detecting chemically specific NMR signals at ultra-low frequencies paving the way for portable noninvasive diagnostics in microscopic sample volumes for biomedicine, industrial sensing through metal enclosures, and field-deployable quantum analytical devices.