Multiparametric Quantum Sensing of Liquids Using NV Centres and Tethered Magnetic Nanoparticles

We propose a new concept for non-invasive, multiparametric liquid analysis based on nitrogen-vacancy (NV) centre magnetometry, relaxometry and surface-tethered magnetic nanoparticles. Magnetic nanoparticles are anchored to a diamond surface via DNA strands, forming nanoscale mechanical oscillators whose thermally driven motion is strongly influenced by the surrounding liquid environment. The resulting time-dependent magnetic fields couple to near-surface NV centres and are detected via optically detected magnetic resonance or changes in spin coherence time. By spatially patterning the diamond surface with regions functionalised by DNA tethers of different lengths, sequences, or chemical modifications, a single liquid is mapped onto a high-dimensional quantum response vector rather than a single scalar observable. Changes in viscosity, molecular adsorption, or chemical interactions modify the dynamics of magnetic nanoparticles in a region-specific manner, enabling differential sensing across the surface. We outline the physical transduction mechanism, discuss relevant scaling relations, and assess experimental feasibility using established wide-field NV magnetometry and relaxometry methods. The proposed platform combines quantum sensing with surface heterogeneity, offering a versatile route toward parallel, label-free liquid characterisation.