Widefield relaxometry with phosphorus doped NV sensor
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Copyright 2019 SPIE. Nitrogen vacancy (NV) centers have amassed considerable interest as biologically compatible magnetometers. NV centers are point defects consisting of a substituted nitrogen adjacent to a vacancy in diamond's lattice. These defects exhibit an optically addressable magnetic field response at room temperature, a process known as optically detected magnetic resonance (ODMR). We take advantage of the imbalanced probability of the excited magnetic spin 1 state to transition to the ground magnetic spin 0 state through an intermediate secondary singlet pathway in NV color centers. This alternative intersystem relaxation response can provide a source of contrast for live-cell imaging with potential nano-scale resolution, as well as for measuring low concentrations of paramagnetic ions. Paramagnetic molecules generate random magnetic field fluctuations which result in a non-zero RMS field. These fluctuations can induce spin relaxation in NVs in the near field of such paramagnetic molecules. This technique is applied at room temperature without microwave control frequencies or induced magnetic fields. The relaxation time for a bulk NV sensor doped with phosphorus was measured, which compared well with referenced values. Phosphorus doping in NV diamond allows the excitation wavelength to be red shifted for a less cytotoxic effect. ODMR spectra were acquired with a helium neon (HeNe) laser.
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Synthesis and Photonics of Nanoscale Materials XVI