Surface-NMR with quantum sensors

近年来，金刚石色心已被证明是一种优秀的原子级磁场传感器。由于金刚石中的这些缺陷-更准确地说是氮空位（NV）中心-已经检测到来自几立方纳米样品体积或甚至单个质子的核磁共振（NMR）信号。虽然这种创新的技术，起源于量子光学，似乎是一个非常有前途的工具，化学和生命科学，它还没有被应用到解决这些领域的科学问题。在这里，金刚石量子传感器将用于跨学科研究小组，以建立用于（生物）化学应用的表面敏感NMR技术。与该领域以前的大多数研究相比，这些研究基于单个NV中心，位于表面下方几纳米处的金刚石中的高密度NV层将用于该提议，这大大提高了灵敏度。这种NV层探测来自几纳米厚的表面层的NMR信号，这是传统NMR方法所不可能实现的。表面NV-NMR技术在化学和生命科学中的应用主要有三个方向：（1）表面束缚分子的结构分析。纳米级NV-NMR通常产生宽共振线（kHz），这是由于样品的分子扩散导致核自旋与NV传感器的短相互作用时间。这种扩散线加宽将通过将分子束缚到金刚石表面来克服，这将使线宽减小到10-100 Hz。通过这种方法，表面固定化催化剂的结构将被阐明，这是目前的方法无法解决的任务。(2)探测NV-金刚石表面单脂双层的结构和动力学。在研究了表面支持的脂质双层之后，最终的目标将是用NV-NMR以无标记和显微镜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技术对金刚石表面的铂薄膜进行了检测，并将不同厚度的铂薄膜与其材料性质进行了关联。此外，还将探讨铂的表面分子吸附过程。总之，量子传感器应在化学中建立，用于探测表面的非侵入性（生物）分子和材料特性，这无法用传统的NMR技术解决。这将通过量子技术和化学（合成）方法的独特和跨学科组合来实现。

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.