Oshimi Keisuke, Ishiwata Hitoshi, Nakashima Hiromu, Mandić Sara, Kobayashi Hina, Teramoto Minori, Tsuji Hirokazu, Nishibayashi Yoshiki, Shikano Yutaka, An Toshu, Fujiwara Masazumi
Department of Chemistry, Graduate School of Life, Environmental, Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
The National Institutes for Quantum Science and Technology (QST), Institute for Quantum Life Science (iQLS), Chiba 263-8555, Japan.
ACS Nano. 2024 Dec 31;18(52):35202-35213. doi: 10.1021/acsnano.4c03424. Epub 2024 Dec 16.
Optically accessible spin-active nanomaterials are promising as quantum nanosensors for probing biological samples. However, achieving bioimaging-level brightness and high-quality spin properties for these materials is challenging and hinders their application in quantum biosensing. Here, we demonstrate bright fluorescent nanodiamonds (NDs) containing 0.6-1.3-ppm negatively charged nitrogen-vacancy (NV) centers by spin-environment engineering via enriching spin-less C-carbon isotopes and reducing substitutional nitrogen spin impurities. The NDs, readily introduced into cultured cells, exhibited improved optically detected magnetic resonance (ODMR) spectra; peak splitting () was reduced by 2-3 MHz, and microwave excitation power required was 20 times lower to achieve a 3% ODMR contrast, comparable to that of conventional type-Ib NDs. They show average spin-relaxation times of = 0.68 ms and = 3.2 μs (1.6 ms and 5.4 μs maximum) that were 5- and 11-fold longer than those of type-Ib, respectively. Additionally, the extended relaxation times of these NDs enable shot-noise-limited temperature measurements with a sensitivity of approximately . The combination of bulk-like NV spin properties and enhanced fluorescence significantly improves the sensitivity of ND-based quantum sensors for biological applications.
光学可及的自旋活性纳米材料有望成为用于探测生物样品的量子纳米传感器。然而，要使这些材料达到生物成像级别的亮度和高质量的自旋特性具有挑战性，这阻碍了它们在量子生物传感中的应用。在此，我们通过富集无自旋的碳 - 碳同位素和减少替代氮自旋杂质，利用自旋环境工程展示了含有0.6 - 1.3 ppm带负电荷氮空位（NV）中心的明亮荧光纳米金刚石（NDs）。这些易于引入培养细胞的NDs表现出改善的光探测磁共振（ODMR）光谱；峰分裂（）减少了2 - 3 MHz，实现3%的ODMR对比度所需的微波激发功率降低了20倍，与传统I b型NDs相当。它们的平均自旋弛豫时间分别为 = 0.68 ms和 = 3.2 μs（最大值分别为1.6 ms和5.4 μs），分别比I b型长5倍和11倍。此外，这些NDs延长的弛豫时间使得能够进行散粒噪声限制的温度测量，灵敏度约为 。块状NV自旋特性与增强荧光的结合显著提高了基于ND的量子传感器在生物应用中的灵敏度。
