Biocompatible Vaterite Carriers Enable Multimodal Quantum Sensing with Nanodiamonds

Abstract:Mobile nanodiamond quantum sensors in liquids are affected by Brownian rotation, variable photon collection, and perturbations from optical trapping. Here we assemble 40-nm nitrogen-vacancy nanodiamonds on porous, birefringent vaterite microspherulites, creating mobile sensors with a polarization-addressable body frame and a chemically active carbonate interface. Under 976-nm trapping, the sensors retain spin resonance and longitudinal relaxation, with less than 7% variation in contrast and an approximately 1-MHz resonance shift at 0.8 W. Zeeman-split resonances resolve magnetic fields from 0 to 0.8 mT, with a response metric of 78--144 $\mu$T Hz$^{-1/2}$. In cell-culture medium, a 10.7-$\mu$M proton-equivalent dose shortens $T_1$ from $23.4 \pm 2.3$ to $9.0 \pm 1.2$ $\mu$s, yielding concentration and pH sensitivities of $6.46$ $\mu$M Hz$^{-1/2}$ and $6.54$ mpH Hz$^{-1/2}$, respectively. A 500-fold larger proton dose in ethanol produces a weaker response. A grand-canonical charge-regulation model links proton chemical potential to interfacial switching, establishing a route to multimodal quantum sensing in complex liquids.

arXiv:2608.09434 [quant-ph]

(or arXiv:2608.09434v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2608.09434 Focus to learn more arXiv-issued DOI via DataCite

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