School of Chemistry and Bio21 Molecular Science and Biotechnology Institute , The University of Melbourne , Parkville , Victoria 3010 , Australia.
Department of Physics, Astronomy and Medical Radiation Science , Curtin University , Bentley , Western Australia 6102 , Australia.
ACS Appl Mater Interfaces. 2018 Apr 18;10(15):13143-13149. doi: 10.1021/acsami.7b19238. Epub 2018 Apr 5.
Nanoscale quantum probes such as the nitrogen-vacancy (NV) center in diamonds have demonstrated remarkable sensing capabilities over the past decade as control over fabrication and manipulation of these systems has evolved. The biocompatibility and rich surface chemistry of diamonds has added to the utility of these probes but, as the size of these nanoscale systems is reduced, the surface chemistry of diamond begins to impact the quantum properties of the NV center. In this work, we systematically study the effect of the diamond surface chemistry on the quantum coherence of the NV center in nanodiamonds (NDs) 50 nm in size. Our results show that a borane-reduced diamond surface can on average double the spin relaxation time of individual NV centers in nanodiamonds when compared to thermally oxidized surfaces. Using a combination of infrared and X-ray absorption spectroscopy techniques, we correlate the changes in quantum relaxation rates with the conversion of sp carbon to C-O and C-H bonds on the diamond surface. These findings implicate double-bonded carbon species as a dominant source of spin noise for near surface NV centers. The link between the surface chemistry and quantum coherence indicates that through tailored engineering of the surface, the quantum properties and magnetic sensitivity of these nanoscale systems may approach that observed in bulk diamond.
在过去十年中，随着对这些系统的制造和操控的控制不断发展，纳米级量子探针（如钻石中的氮空位（NV）中心）已经证明了其在传感方面的卓越能力。钻石的生物相容性和丰富的表面化学性质增加了这些探针的实用性，但随着这些纳米级系统的尺寸减小，钻石的表面化学性质开始影响 NV 中心的量子特性。在这项工作中，我们系统地研究了钻石表面化学对 50nm 纳米钻石中 NV 中心量子相干性的影响。我们的结果表明，与热氧化表面相比，硼烷还原的钻石表面平均可以将单个 NV 中心在纳米钻石中的自旋弛豫时间延长一倍。我们使用红外和 X 射线吸收光谱技术相结合的方法，将量子弛豫率的变化与钻石表面 sp 碳转化为 C-O 和 C-H 键的情况相关联。这些发现表明，双键碳物种是近表面 NV 中心自旋噪声的主要来源。表面化学与量子相干性之间的联系表明，通过对表面进行有针对性的工程设计，这些纳米级系统的量子特性和磁敏度可能接近在块状钻石中观察到的特性。
