arXiv subjects

Erin S. Grant

Publications and source records attributed to Erin S. Grant.

4 recordsLinked to original sources

arXiv2026

Optical spin defect pairs in cubic boron nitride

Room-temperature optically active solid-state spin defects are widely known to be useful in quantum sensing applications, however, only a select range of materials have been found to host such systems. Recent measurements in the van der Waals material hexagonal boron nitride (hBN) have shown optically detected magnetic resonance (ODMR) with spin-1/2-like signatures can be explained by a charge transfer mechanism where charges move between adjacent defects forming weakly coupled spin pairs. Interestingly, these ODMR signatures have been reported in a variety of materials aside from hBN, suggesting the spin pair model provides a potentially material agnostic approach for enabling ODMR. Here, we test whether the charge transfer mechanism is supported in a different crystal phase, and report on ODMR signatures in cubic boron nitride (cBN), showing all the characteristic properties identified in hBN are preserved. We consider a selection of different cBN samples of varying size and observe ODMR from a single sub-micron cBN particle, paving the way towards sensing applications. This work further expands understanding of the ubiquity of optical spin defect pairs, and establishes the potential for exploring quantum technologies with a wider range of materials.

cond-mat.mes-hall↗

arXiv2026

Method for real-time monitoring of paramagnetic reactions using spin relaxometry with fluorescent nanodiamonds

Spin relaxometry using fluorescent nanodiamonds (FNDs) has been applied successfully to sense numerous paramagnetic target molecules such as free radicals and metalloproteins. However, despite their high sensitivity, T1 spin relaxation measurements are often hampered by their slow acquisition speed. Here, we demonstrate a method that allows for real-time monitoring of paramagnetic chemical reactions. We demonstrate T1 spin relaxometry from thousands of FNDs using an optimised cuvette-based system integrating an avalanche photodiode operated in linear mode, and a fast, fieldprogrammable gate array (FPGA) for data collation. We demonstrate chemical monitoring of the reduction of Cu(II) to Cu(I) ions in-solution with a 15 second integration using an optimised T1 sensing protocol. Our method achieves more than two orders of magnitude speed up with an order of magnitude reduction in cost when compared with traditional techniques. With further technical improvements, we believe this in-solution method could be extended to sense the sub-second chemical kinetics of paramagnetic molecules in solution.

cond-mat.mes-hall↗

arXiv2025

Spin-dependent photoluminescence in carbon-based quantum dots

The ability to modulate the photoluminescence (PL) of nanomaterials via spin-related effects is vital for many emerging quantum technologies, with nanoscale quantum sensing and imaging being particular areas of focus. Carbon-based quantum dots (CQDs) are among the most common forms of luminescent nanomaterials, appealing due to their ease of synthesis, tunability through organic chemistry, high brightness, and natural biocompatibility. However, the observation of room temperature, spin-dependent PL has remained elusive. Here we report on the observation of PL modulation of CQDs by magnetic fields ($\sim 10$ mT) under ambient conditions. We synthesize a series of CQDs using 19 different amino acids, which have a range of PL emission spectra and exhibit a clear magneto-PL effect (up to $\sim 1$% change). Furthermore, an electron spin resonance is detected in the PL with a g-factor of g $\approx$ 2, suggesting a process similar to the radical pair mechanism is responsible. Finally, we show that the magneto-PL contrast decreases in the presence of paramagnetic species, which we attribute to an increase in magnetic noise-induced spin relaxation in the CQDs. Our work brings new functionalities to these commonly used and biocompatible luminescent nanoparticles, opening new opportunities for in situ quantum sensing and imaging of biological samples.

cond-mat.mes-hall↗

arXiv2025

Self-assembled fluorescent nanodiamond layers for quantum imaging

The nitrogen-vacancy (NV) center in diamond is emerging as a powerful tool for imaging magnetic and electric signals at the microscale and below. However, most imaging demonstrations thus far have relied on costly, millimeter-sized bulk diamond substrates, which cannot be easily scaled or integrated with other materials. Here, we report a scalable method for fabricating NV-containing dense and homogenous fluorescent nanodiamond (FND) layers through electrostatic self-assembly and demonstrate the utility of the FND layers for magnetic imaging. We investigate the effect of FND concentration in suspension, substrate immersion time, and solvent pH on the FND density on the substrate. We identify optimized self-assembly conditions that maximize the FND density while minimizing aggregation. Using FND layers on a quartz substrate, we demonstrate magnetic field and magnetic noise imaging at the microscale, based on NV optically detected magnetic resonance magnetometry and T$_1$ relaxometry, respectively. Our results provide a direction for the development of cost-effective and scalable FND layers and surface coatings. This paves the way for on-demand quantum sensing and imaging on a broad range of surfaces based on NV centers and other diamond quantum emitters.

cond-mat.mes-hall↗