Spin‐Enhanced Magneto‐Plasmonic Nanodiamonds With Accelerated Capture for Ultrafast Attomolar Biosensing

ABSTRACT Rapid and single‐molecule detection of low‐abundance biomarkers is crucial to accurate early cancer diagnosis, yet remains hindered by the slow biomolecule binding and pervasive background interference in complex biofluids. To address the challenges, we construct a magneto‐plasmonic fluorescent nanodiamonds (MPFNDs) platform that enables accelerated target capture and high‐fidelity quantum sensing. The MPFND probes, engineered by assembling gold‐magnetic nanoparticles (GMPs) onto nanodiamonds hosting nitrogen‐vacancy (NV) centers, utilize superparamagnetism to accelerate biomolecule binding on a monolayer silver nanoisland array (MSNA) and reduce incubation time to 15 min, while suppressing nonspecific noise by 68.7%. The distinct plasmonic modules offer independent enhancement of quantum charge state emission and spin fidelity: the MSNA selectively amplifies the zero‐phonon line of neutral NV centers (NV ⁰ ) by 89.4‐fold, while GMPs manipulate the spin environment of the negative NV centers (NV ⁻ ), yielding a 6.7‐fold gain in optically detected magnetic resonance (ODMR) contrast. Such dual‐quantum enhancement allows rapid target localization via NV ⁰ imaging and precise identification through ODMR measurement. As a proof‐of‐concept, the platform achieves attomolar (53 aM) detection of microRNA‐21 in serum. By integrating these innovative designs, this work establishes a versatile nanomaterial strategy for ultrafast, ultrasensitive biosensing, opening new pathways for clinical diagnosis and quantum‐enabled nanophotonics.