Stable ensemble emission from nitrogen vacancy (NV) centers in nanodiamonds (NDs) is highly desirable for diverse areas ranging from bio-imaging to quantum optics. The uniqueness of NV centers lies in their opto-spin properties like energy level structure, emission range (620-850 nm) and optical spin polarization. The host matrix (NDs), however, put some limitation on the photo-physical properties of these color centers. One of the major issues is surface proximity (where high concentration of defects are present) of NV centers. The NV centers being highly sensitive to the neighboring environment are unstable in such circumstances. The surface of NDs mainly exhibit non-diamond carbon which is well-known quencher of emission due to NV centers. The surface composition for desirable photo-physical properties of NV centers is still unknown. Here, we have systemically studied the effect of oxidation time at low oxidation temperature (450 ^oC) on the selective removal of sp² carbon, aqueous dispersion of NDs and emission collection due to NV centers at ensemble level. Among different air oxidations, heat treatment at 450 ^oC at residual time of 8 hours has been found to be suitable air oxidation conditions for the enhancement of brightness and ensemble photo-stability of NV centers.

中文翻译：

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通过优化表面组成，从纳米金刚石中的氮空位中心获得稳定的整体亮度

从生物成像到量子光学的各个领域，都非常需要纳米金刚石（NDs）中的氮空位（NV）中心稳定的集合发射。NV中心的独特之处在于它们的光自旋特性，例如能级结构，发射范围（620-850 nm）和光学自旋偏振。但是，主体基质（ND）对这些色心的光物理性质施加了一些限制。主要问题之一是NV中心的表面接近度（存在大量缺陷）。在这种情况下，对邻近环境高度敏感的NV中心不稳定。ND的表面主要表现出非金刚石碳，这是由于NV中心导致的众所周知的发射猝灭剂。用于NV中心的理想光物理性质的表面组成仍然未知。这里，^o C）选择性去除sp ^2的碳，NDs的水分散体以及由于整体中心的NV中心而产生的排放物。在不同的空气氧化中，发现在450 ^o C的残留时间8小时内进行热处理是提高NV中心亮度和整体光稳定性的合适空气氧化条件。