Nanoscale spin detection of copper ions using double electron-electron resonance at room temperature

We report the nanoscale spin detection and electron paramagnetic resonance (EPR) spectrum of copper (Cu2+) ions via double electron-electron resonance (DEER) with single spins in diamond at room temperature and low magnetic fields. We measure unexpectedly narrow EPR resonances with linewidths similar to 2 - 3 MHz from copper chloride molecules dissolved in polylysine. We also observe coherent Rabi oscillations and hyperfine splitting from single Cu2+ ions, which could be used for dynamic nuclear spin polarization and higher sensitivity of spin detection. We interpret and analyze these observations using both spin Hamiltonian modeling of the copper chloride molecules and numerical simulations of the predicted DEER response, and obtain a sensing volume similar to(250 nm)(3). This work will open the door for copper-labeled EPR measurements under ambient conditions in biomolecules and nanomaterials.

Automated summary

This study successfully demonstrated nanoscale spin detection and EPR spectrum of copper ions using DEER technique in diamond, with unexpectedly narrow EPR resonances and coherent Rabi oscillations observed. These findings suggest potential applications in dynamic nuclear spin polarization and higher sensitivity of spin detection in biomolecules and nanomaterials.