Electron paramagnetic resonance microscopy using spins in diamond under ambient conditions

Magnetic resonance spectroscopy is one of the most important tools in chemical and bio-medical research. However, sensitivity limitations typically restrict imaging resolution to ~ 10 µm. Here we bring quantum control to the detection of chemical systems to demonstrate high-resolution electron spin imaging using the quantum properties of an array of nitrogen-vacancy centres in diamond. Our electron paramagnetic resonance microscope selectively images electronic spin species by precisely tuning a magnetic field to bring the quantum probes into resonance with the external target spins. This provides diffraction limited spatial resolution of the target spin species over a field of view of 50 × 50 µm(2) with a spin sensitivity of 10(4) spins per voxel or ∼100 zmol. The ability to perform spectroscopy and dynamically monitor spin-dependent redox reactions at these scales enables the development of electron spin resonance and zepto-chemistry in the physical and life sciences.