Surface-NMR with quantum sensors

近年来，金刚石中的色心已被证明是一种出色的原子尺度磁场传感器。利用金刚石中的这些缺陷——更准确地说是氮空位（NV）中心——从几个立方纳米体积的样品甚至单个质子中检测到核磁共振（NMR）信号。虽然这种源于量子光学的创新技术似乎是化学和生命科学中非常有前途的工具，但它尚未应用于解决这些领域的科学问题。在这里，金刚石量子传感器应使用在一个跨学科的研究小组中建立了一种表面敏感的核磁共振技术，用于（生物）化学应用。与该领域之前大多数基于单个nv中心的研究不同，该方案将在金刚石表面以下几纳米处使用高密度的nv层，这将大大提高灵敏度。该nv层探测几个纳米厚的表面层的核磁共振信号，这是传统核磁共振方法无法实现的。表面NV-NMR技术在化学和生命科学领域的应用有三个方向：(1)表面系留分子的结构分析。纳米级NV-NMR的结果通常是宽共振线（kHz），因为原子核自旋与nv传感器的相互作用时间短，这是样品分子扩散的结果。在这里，通过将分子拴在金刚石表面来克服这种扩散线宽，这将使线宽减少到10-100赫兹。用这种方法可以阐明表面固定化催化剂的结构，这是现有方法无法解决的问题。(2)探索nv -金刚石表面单脂双分子层的结构和动力学。在研究了表面支持的脂质双分子层之后，最终的目标将是用NV-NMR以无标签和微观的方式确定活细胞的膜结构。(3)催化活性表面的研究。利用NV-NMR对金刚石表面的铂薄膜进行检测，并将其材料性能与不同薄膜厚度相关联。此外，还需探索铂表面分子吸附过程。综上所述，量子传感器将在化学领域建立，用于探测表面的非侵入性（生物）分子和材料特性，这是传统核磁共振技术无法解决的。这将通过量子技术和化学（合成）方法的独特跨学科结合来实现。

In recent years, color centers in diamond have been shown to be an outstanding atomic-scale sensor for magnetic fields. With these defects in diamond – more precisely nitrogen vacancy (NV) centers – nuclear magnetic resonance (NMR) signals from a few cubic nanometer sample volumes or even single protons have been detected. Although this innovative technique, originating from quantum optics, seems to be a very promising tool for chemical and life sciences, it has not been yet applied to solve scientific questions in these fields. Here, the diamond quantum sensors shall be used in an interdisciplinary research group to establish a surface sensitive NMR technology for (bio)chemical applications. In contrast to most of the previous studies in this field, which were based on single NV-centers, a high-dense NV-layer in diamond, located a few nanometers beneath the surface, will be used for this proposal, which increases sensitivity dramatically. This NV-layer probes NMR signals from a few nanometer-thick surface layer, which is not possible with traditional NMR methods. The surface NV-NMR technology shall be applied to three directions in chemical and life science applications: (1) Structural analysis of surface tethered molecules. Nanoscale NV-NMR results usually in broad resonance lines (kHz) due to short interaction times of the nuclear spin with the NV-sensor, as a consequence of the molecular diffusion of the sample. This diffusional line broadening will be overcome here by tethering molecules to the diamond surface, which will reduce the linewidth to 10-100 Hz. With this approach structures of surface immobilized catalysts shall be elucidated, a task which cannot be addressed with current methods. (2) Probing structure and dynamics of single lipid bilayers on the NV-diamond surface. After investigating surface supported lipid bilayers, the ultimate aim will be to determine membrane structures of living cells in a label free and microscopic way with NV-NMR. (3) Investigation of catalytic active surfaces. Thin platinum films on diamond will be sensed with NV-NMR and its material properties will be correlated with different film thicknesses. Moreover, surface molecular adsorption processes on platinum shall be probed. In summary, quantum sensors shall be established in chemistry for probing non-invasively (bio)molecular and material properties at surfaces, which cannot be addressed with traditional NMR techniques. This will be achieved through a unique and interdisciplinary combination of quantum technology and chemical (synthetic) methods.