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Abstract Understanding the behavior of confined water at liquid–solid interfaces is central to numerous physical, chemical, and biological processes, yet remains experimentally challenging. Here, shallow nitrogen‐vacancy (NV) centers in diamond serve as sensors to investigate the nanoscale dynamics of interfacial water confined between the diamond surface and an overlying fluorinated oil droplet. With the help of nuclear magnetic resonance (NMR) protocols selectively sensitive to¹H and¹⁹F, NVs are used to probe water and oil near the interface under ambient conditions. Comparing opposite sides of a doubly‐implanted diamond membrane — one exposed to oil, the other not — a slow, multi‐day process is uncovered in which the interfacial water layer is gradually depleted. This desorption appears to be driven by sustained interactions with the fluorinated oil and is supported by molecular dynamics simulations and surface‐sensitive X‐ray spectroscopies. These findings provide molecular‐level insight into long‐timescale hydration dynamics and underscore the power of NV‐NMR for probing liquid–solid heterointerfaces with chemical specificity. 

Abstract Two‐dimentional magnets are of significant interest both as a platform for exploring novel fundamental physics and for their potential in spintronic and optoelectronic devices. Recent bulk magnetometry studies have indicated a weak ferromagnetic response in tungsten disulfide (WS₂), and theoretical predictions suggest edge‐localized magnetization in flakes with partial hydrogenation. Here, room‐temperature wide‐field quantum diamond magnetometry to image pristine and Fe‐implanted WS₂flakes of varying thicknesses (45–160 nm), exfoliated from bulk crystals and transferred to NV‐doped diamond substrates, is used. Direct evidence of edge‐localized stray magnetic fields, which scale linearly with applied external magnetic field (4.4–220 mT), reaching up to ±4.7 µT, is observed. The edge signal shows a limited dependence on the flake thickness, consistent with dipolar field decay and sensing geometry. Magnetic simulations using five alternative models favor the presence of edge magnetization aligned along an axis slightly tilted from the normal to the WS₂flake's plane, consistent with spin canting in antiferromagnetically coupled edge states. Thses findings establish WS₂as a promising platform for edge‐controlled 2D spintronics. 

Abstract Extending the coherence lifetime of a qubit is central to the implementation and deployment of quantum technologies, particularly in the solid state where various noise sources intrinsic to the material host play a limiting role. This study examines theoretically the coherent spin dynamics of a hetero‐spin system formed by a spin featuring a non‐zero crystal field and in proximity to a paramagnetic center . An analysis of the energy level structure of the dyad shows this system exhibits apair of levels separated by a magnetic‐field‐insensitive energy gap, which can be exploited to create long‐lived zero‐quantum coherences. It is found that these coherences are selectively sensitive to “local”—as opposed to “global”—magnetic field fluctuations, suggesting these spin dyads can serve as a nanoscale gradiometer for precision magnetometry. On the other hand, the distinct response of either spin species to electric or thermal stimuli allows one to implement alternative sensing protocols for magnetic‐noise‐free electrometry and thermometry. 

High-temperature annealing is a promising but still mainly unexplored method for enhancing spin properties of negatively charged nitrogen-vacancy (NV) centers in diamond particles. After high-energy irradiation, the formation of NV centers in diamond particles is typically accomplished via annealing at temperatures in the range of 800–900 °C for 1–2 h to promote vacancy diffusion. Here, we investigate the effects of conventional annealing (900 °C for 2 h) against annealing at a much higher temperature of 1600 °C for the same annealing duration for particles ranging in size from 100 nm to 15 μm using electron paramagnetic resonance and optical characterization. At this high temperature, the vacancy-assisted diffusion of nitrogen can occur. Previously, the annealing of diamond particles at this temperature was performed over short time scales because of concerns of particle graphitization. Our results demonstrate that particles that survive this prolonged 1600 °C annealing show increased NV T1 and T2 electron spin relaxation times in 1 and 15 μm particles, due to the removal of fast relaxing spins. Additionally, this high-temperature annealing also boosts magnetically induced fluorescence contrast of NV centers for particle sizes ranging from 100 nm to 15 μm. At the same time, the content of NV centers is decreased fewfold and reaches a level of <0.5 ppm. The results provide guidance for future studies and the optimization of high-temperature annealing of fluorescent diamond particles for applications relying on the spin properties of NV centers in the host crystals.