Work

Solution-phase fluorination of nanodiamond: Near-surface NV− activation and spin relaxation

Year: 2026

Type: article

Abstract: Nanodiamonds hosting luminescent point defects, known as fluorescent nanodiamonds (FND), are a leading platform for quantum technology. The nitrogen–vacancy (NV) centre is the most intensively studied of these; its negatively charged state (NV – ) can serve as a qubit at room temperature, and its stability is governed by surface functional groups. We present two solution-phase fluorination routes for stabilising NV – : direct C–F bond formation by decarboxylation with xenon difluoride via a radical mechanism, and the Balz–Schiemann reaction, which replaces surface amino groups with fluorine. The two routes were compared by infrared, X-ray photoelectron, energy-dispersive X-ray, Raman and photoluminescence spectroscopy. Both gave a high NV – fraction, up to ∼ 85% on average, which to our knowledge is among the highest reported for surface-terminated nanodiamonds of this size and, in particular, for fluorine termination. We attribute the stabilisation to the fluorination treatment, which removes acceptor-like carboxyl groups and forms C–F bonds that give the surface a positive electron affinity. Frequency-domain relaxometry shows that the fluorinated particles retain a long spin–lattice relaxation time, 733 ± 56 and 712 ± 20 μ s for the XeF 2 and Balz–Schiemann routes, several times the values reported for commercial HPHT nanodiamonds, although shorter than the 1173 ± 123 μ s of the as-received material. Fluorination thus activates near-surface NV – centres, which dominate relaxometric sensing, at the cost of a moderate shortening of T 1 .

Source: Carbon

DOI: 10.1016/j.carbon.2026.122262