Contrast Induced by a Static Magnetic Field for Improved Detection in Nanodiamond Fluorescence Microscopy

Abstract

Diamond nanoparticles with negatively charged nitrogen-vacancy (NV) centers are highly efficient nonblinking emitters that exhibit spin-dependent intensity. An attractive application of these emitters is background-free fluorescence microscopy exploiting the fluorescence quenching induced either by resonant microwaves (RMWs) or by an applied static magnetic field (SMF). Here, we compare RMWand SMF-induced contrast measurements over a wide range of optical excitation rates for fluorescent nanodiamonds (FNDs) and for NV centers shallowly buried under the (100)-oriented surface of a diamond single crystal (SC). Contrast levels are found to be systematically lower in the FNDs than in the SC. At low excitation rates, the RMW contrast initially rises to a maximum (up to 7% in FNDs and 13% in the SC) but then decreases steadily at higher intensities. Conversely, the SMF contrast increases from approximately 12% at low excitation rates to high values of 20% and 38% for the FNDs and SC, respectively. These observations are well described in a rate-equations model for the charged NV defect using parameters in good agreement with the literature. The SMF approach yields higher induced contrast in image collection under commonly applied optical excitation. Unlike the RMW method, there is no thermal load exerted on the aqueous media in biological samples in the SMF approach. We demonstrate imaging by SMF-induced contrast in neuronal cultures incorporating FNDs (i) in a setup for patch-clamp experiments in parallel with differential-interference-contrast microscopy, (ii) after a commonly used staining procedure as an illustration of the high selectivity against background fluorescence, and (iii) in a confocal fluorescence microscope in combination with bright-field microscopy.

Diamonds levitating in a Paul trap under vacuum: Measurements of laser-induced heating via NV center thermometry

“…The ESR contrast starts at 2.5 % at 50µW and reduces to 1% at 700 µW . Let us note that, in the range of laser powers used in the experiment, no change in the ESR contrast or width was observed under atmospheric conditions [27,28]. The drop in the contrast can thus be attributed to an increased temperature of the diamond.…”

Optically Detected Magnetic Resonance for Selective Imaging of Diamond Nanoparticles

“…ODMR is important for imaging applications because it provides a way to selectively modulate the intensity of N V -containing nanodiamonds using relatively weak microwave fields, while the vast majority of other fluorescent moieties remain unaffected by the microwaves. Thus, ODMR provides a way to selectively identify fluorescence from diamond nanoparticles in the presence of autofluorescence, scattering, and other spectrally overlapped background signals. , In addition to imaging in biological systems, ,, ODMR can also be used in principle as a probe of local magnetic fields, − electric fields, spin, and temperature . Thus, ODMR in nanodiamond has great potential as a quantum-based analytical tool for addressing a wide range of analytical sensing and selective imaging problems.…”

“…Thus, ODMR provides a way to selectively identify fluorescence from diamond nanoparticles in the presence of autofluorescence, scattering, and other spectrally overlapped background signals. 28,31 In addition to imaging in biological systems, 29,32,33 ODMR can also be used in principle as a probe of local magnetic fields, 34−38 electric fields, 39 spin, 40 and temperature. 41 Thus, ODMR in nanodiamond has great potential as a quantum-based analytical tool for addressing a wide range of analytical sensing and selective imaging problems.…”

High Temperature Treatment of Diamond Particles Toward Enhancement of Their Quantum Properties

“…Notably, a significant dependence of the hyperpolarization capability in high-temperature annealed particles with the highest hyperpolarization enhancement for particles treated in the 1700 • C−1750 • C range was recently observed as well [36]. Herein, we expand our initial studies on the impact of hightemperature annealing [29,30] and relate to the development of significantly increased diamond particle hyperpolarizability [37] to other quantum properties of NV − centers in fluorescent particulate diamond, specifically magnetic modulation of the particle's fluorescence [12,13,[38][39][40][41][42]. It is envisioned that this method will facilitate identification of fluorescent diamond particle sensors in biological environments with high fluorescent background and light scattering capability.…”