RESUMEN

Nitrogen-vacancy (NV) magnetometry offers an alternative tool to detect paramagnetic centers in cells with a favorable combination of magnetic sensitivity and spatial resolution. Here, we employ NV magnetic relaxometry to detect cytochrome C (Cyt-C) nanoclusters. Cyt-C is a water-soluble protein that plays a vital role in the electron transport chain of mitochondria. Under ambient conditions, the heme group in Cyt-C remains in the Fe3+ state, which is paramagnetic. We vary the concentration of Cyt-C from 6 to 54 µM and observe a reduction of the NV spin-lattice relaxation time (T1) from 1.2 ms to 150 µs, which is attributed to the spin noise originating from the Fe3+ spins. NV T1 imaging of Cyt-C drop-casted on a nanostructured diamond chip allows us to detect the relaxation rates from the adsorbed Fe3+ within Cyt-C.

Asunto(s)

Citocromos c , Nitrógeno , Magnetismo , Diamante , Fenómenos Magnéticos

RESUMEN

In magnetometry using optically detected magnetic resonance of nitrogen vacancy (NV-) centers, we demonstrate more than one order-of-magnitude speed up with sequential Bayesian experiment design as compared with conventional frequency-swept measurements. The NV- center is an excellent platform for magnetometry with potential spatial resolution down to few nanometers and demonstrated single-defect sensitivity down to nT/Hz1/2. The NV- center is a quantum defect with spin S = 1 and coherence time up to several milliseconds at room temperature. Zeeman splitting of the NV- energy levels allows detection of the magnetic field via photoluminescence. We compare conventional NV- center photoluminescence measurements that use pre-determined sweeps of the microwave frequency with measurements using a Bayesian inference methodology. In sequential Bayesian experiment design, the settings with maximum utility are chosen for each measurement in real time based on the accumulated experimental data. Using this method, we observe an order of magnitude decrease in the NV- magnetometry measurement time necessary to achieve a set precision.

RESUMEN

We describe a real-time method to obtain normalized differential count rate signals from modulated systems with photon detection at single-photon count rates. The method is demonstrated with a real-time peak-locking and frequency control to track magnetic field using optically detected magnetic resonance of nitrogen-vacancy centers in diamond. This procedure allows us to measure the magnetic field continuously with a sensitivity of 4.1 µT/Hz1/2 and to track magnetic field sweep rates up to 50 µT/s. The differential rate meter automates the processing of voltage pulse outputs from the photon detector and provides noise levels on par with traditional photon counting methods using digital counters.