发表机构
Óbuda University; HUN-REN Wigner Research Centre for Physics, Institute for Solid State Physics and Optics; Budapest University of Technology and Economics; HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science; Kandó Kálmán Faculty of Electrical Engineering, Óbuda University（欧贝达大学; 匈牙利研究与教育网络维格纳物理研究中心固体物理与光学研究所; 布达佩斯技术与经济大学; 匈牙利研究与教育网络能源研究中心技术物理与材料科学研究所; 欧贝达大学坎多·卡尔曼电气工程学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出两种溶液相氟化方法稳定纳米金刚石近表面NV$^-$中心，实现高负电荷态比例（约90%），同时保持较长自旋弛豫时间，但发现电荷稳定性与自旋寿命不协同提升。
AI 中文摘要
承载发光点缺陷的纳米金刚石，即荧光纳米金刚石（FND），是量子技术的主要平台。其中，氮-空位（NV）中心是研究最为深入的缺陷；其负电荷态（NV$^-$）在室温下可作为量子比特，其稳定性由表面官能团决定。我们提出了两种稳定NV$^-$的溶液相氟化路线：通过二氟化氙脱羧直接形成C-F键的自由基机制，以及Balz-Schiemann反应，该反应将表面氨基替换为氟。通过红外光谱、X射线光电子能谱、能量色散X射线能谱、拉曼光谱和光致发光光谱对两种路线进行了比较。两种路线均获得了高NV$^-$比例，平均高达约90%，在富氟区域接近100%，据我们所知，这是该尺寸表面终止纳米金刚石，特别是氟终止纳米金刚石中报道的最高值之一。频域弛豫测量表明，氟化颗粒保持了较长的自旋-晶格弛豫时间，XeF$_2$和Balz-Schiemann路线分别为$733\pm56$和$712\pm20$ $\mu$s，是商业HPHT纳米金刚石报道值的数倍，但短于原始材料的$1173\pm123$ $\mu$s。因此，电荷态稳定性和自旋寿命并未同时改善：氟化激活了近表面NV$^-$中心，这些中心最易受表面噪声影响，但也主导弛豫传感。
英文摘要
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 $\sim$90% on average and approaching 100% in fluorine-rich regions, which to our knowledge is among the highest reported for surface-terminated nanodiamonds of this size and, in particular, for fluorine termination. Frequency-domain relaxometry shows that the fluorinated particles retain a long spin-lattice relaxation time, $733\pm56$ and $712\pm20$ $μ$s for the XeF$_2$ and Balz-Schiemann routes, several times the values reported for commercial HPHT nanodiamonds, although shorter than the $1173\pm123$ $μ$s of the as-received material. Charge-state stability and spin lifetime therefore do not improve together: fluorination activates near-surface NV$^-$ centres, which are the most exposed to surface noise but also the ones that dominate relaxometric sensing.
Comments22 pages, 12 figures, 5 tables
