Development of DNP enhanced solid-state NMR techniques for the characterization of functionalized cellulose-based materials

纤维素基或纸基功能化材料在微流体和生物医学传感方面具有巨大的应用潜力。它们的设计需要对纳米级的结构和表面功能化有详细的了解，这需要适当的表征技术。因此，本项目提案的目标是开发以纤维素为基础的功能性材料的研究技术，并将其应用于实际的模型系统。动态核极化(DNP)增强的固体核磁共振技术为研究比表面积小或官能化程度较小的纤维素基体系提供了必要的灵敏度。首先，对一维多核固体DNP核磁共振实验(13C、29Si、15N)的样品制备进行了优化。通过这些实验，探索了二氧化硅对纤维素的化学改性以及连接物分子在纤维素上的共价结合。此外，还确定了DNP实验的灵敏度。此外，观察到的不同官能团的信号放大与样品的宏观润湿行为相关联，以获得关于结构-性质关系的信息。开展了DNP增强的二维实验，例如1H-X HETCOR(X=13C，29Si，15N)，以研究极化剂与表面/表面官能化之间的相互作用。它们与一维实验一起用于研究纳米级二氧化硅或聚合物功能化纤维素中可控毛细管流动的原因。此外，它们还用于研究溶剂对表面修饰的影响，特别是对生物功能化的影响。为了解决纤维素表面生物功能化的复杂结构，将其用作生物传感设备或仿生材料，开发了DNP增强的2D异相关实验(如13C-13C，13C-15N)，为此通常需要对生物成分进行同位素标记。这些实验将提供有关功能化的构象和配置的信息。它们是在氨基酸或多肽功能化的纤维素上进行的。

Cellulose or paper-based functionalized materials have tremendous application potential in microfluidics and bio-medical sensing. Their design necessitates detailed knowledge of the structure and surface functionalization at the nanoscale, which requires appropriate characterization techniques. The objectives of this project proposal are therefore the development of techniques for the investigation of functional cellulose-based materials and their application to practical model systems. Dynamic nuclear polarization (DNP) enhanced solid-state NMR provides the necessary sensitivity for the study of cellulose-based systems with small specific surface areas or small degree of functionalization.The method development is carried out in different steps. First, the sample preparation for 1D multinuclear solid-state DNP NMR experiments (13C, 29Si, 15N) is optimized. With these experiments, the chemical modification of cellulose with silica as well as the covalent attachment of linker molecules on cellulose are explored. Furthermore, the sensitivity of the DNP experiments is determined. In addition, the observed signal amplification of different functional groups is correlated with the macroscopic wetting behavior of the samples to obtain information on the structure-property relationship. DNP enhanced 2D experiments such as e.g. 1H-X HETCOR (X = 13C, 29Si, 15N) are developed to study the interaction between the polarization agent and the surface/surface functionalization. They are used together with the 1D experiments to investigate the causes of controllable capillary flow in silica or polymer functionalized cellulose at the nanoscale. In addition, they serve to investigate the influence of solvents on the surface modification, especially on biofunctionalization.To address the complex structures of biofunctionalizations on cellulose for later applications as a biosensing device or as a biomimetic, DNP enhanced 2D heterocorrelation experiments (e.g. 13C-13C, 13C-15N) are developed, for which an isotopic labeling of the biological component is usually required. These experiments will provide information on the conformation and configuration of the functionalization. They are carried out on amino acid or peptide functionalized cellulose.