Research

Welcome to the Magnetic Resonance Research Center at Radboud University, Nijmegen, The Netherlands. Our  group is part of the Institute for Materials and Molecules. IMM is an interdisciplinary research institute in chemistry and physics at the Radboud University Nijmegen. Its mission is to fundamentally understand, design and control the functioning of molecules and materials. Advancing spectroscopic research and its applications to functional molecules and materials is a top priority of the IMM.

The focus of our  NMR research center is the development and application of nuclear magnetic resonance methods that enable the study of local structure and dynamics in functional materials. The research is structured in three layers. On the highest aggregation level are the applied projects which are mainly focused on polymers and materials for energy storage and conversion. Within these projects the structure directing forces and transport and dynamics can be identified as fundamental underlying concepts that we are exploring to gain an in-depth understanding of the principles that bring a specific functionality to a molecular construct or material. This approach requires appropriate methodology and therefore a considerable amount of the research is directed toward enabling technologies with the ambition to progress from bulk characterization to an approach that allow us to unravel the inner workings of the smallest functional units in relation to the processes and functionalities under investigation. The research can be divided in three main areas:

1) NMR methodology focusing on enhanced sensitivity in both solids and liquids. NMR spectroscopy is a tremendously successful method to study the structure and dynamics of molecules and materials. Nevertheless, the present sensitivity prohibits the study of very small crystals, chemically active surfaces and/or small biological systems. The purpose of our research is to combine miniaturization of NMR detection technology with advanced control of the terms in the spin Hamiltonian to open new fields of research in both spectroscopy and imaging. This is pursued by developing micro Magic Angle Spinning (µMAS) probeheads that allow the study of sample volumes in the nanolitre regime. This not only opens ways to study single crystals or mass-limited samples but also brings novel possibilities for efficient decoupling. Thin film studies require a different approach, for which we have introduced the so-called stripline design. This design is also very useful for performing NMR in a microfluidic context, e.g. to study (fast) reaction kinetics in microreactors. Here it is possible to combine high sensitivity and resolution without compromises. We are exploring the hyphenation of high-sensitivity, sub-µL nuclear magnetic resonance (NMR) detection with supercritical fluid chromatography (SFC). Target applications of this technology are those in analytical science where there is a need for high-throughput chemical characterisation of complex mixtures, but where the substances are available only in very small amounts. To achieve sensitivity enhancements beyond the various new technologies described above demands the implementation of polarization enhancement schemes such as dynamic nuclear polarization. Here miniaturization is again one of the key approaches for a versatile implementation of these methods.

Current work is done by: Koen, Bas, and Fleur

2) Development and Application of NMR Techniques for Quadrupolar Nuclei. In many important research areas, e.g. catalysis, or materials science, quadrupolar nuclei in partly disordered materials are encountered. With the increased interest for NMR of quadrupolar nuclei, many pulse schemes have been adapted to incorporate these nuclei. Sensitivity enhancements by inversion of the satellite transitions prior to excitation of the central transition and QCPMG detection are imperative for addressing realistic applications such as the study of Ziegler-Natta catalysts. For systems with very large quadrupolar interactions, beyond the range accessible by MAS, nutation NMR can play an important role. Here we make use of micro-solenoid and stripline based probes offering tremendously large radio-frequency field strengths in the MHz regime.

Current work is done by: Wouter and Ernst

3) Applications of solid-state NMR in functional materials research. The technique developments described above are not a goal on their own, it is strived to apply the methods in relevant materials research via interdisciplinary collaborations i.e. within the Institute for Molecules and Materials (IMM) and (inter)nationally. The emphasis is on polymers, materials for energy storage and conversion, pharmaceuticals and catalysts.

Linking chemically specific structure information to physical properties of polymers is an important activity in this area. Studies range from detailed characterization of aramids to in-situ tensile tests of polyolefins to understand the effect of comonomers or branches on the mechanical performance of the material. Furthermore we focus on bio(mimicking) materials such as polyisocyanopeptides which serve as scaffolds for various functionalities. Recently novel hydrogels based on functionalized polyisocyanides have been developed by the Molecular Materials group of IMM. We are trying to understand the remarkable properties of these materials by detailed NMR characterization.

In relation to applications to materials, particularly for energy storage and conversion, we study of III-V semiconductor thin films giving us direct insight in the disorder that is present in such materials and relates to its performance. In relation to H-storage we found that nanoconfinement of LiBH4 in porous silica strongly enhances mobility of borohydride anions and lithium. The interactions leading to this effect need to be studied in more detail.

Finally we investigate biomass conversion, i.e. the effects of various thermochemical treatments on the lignocellulosic structure and composition of wheat straw, as well as humin formation in thermal/acidic processing of C6-sugars in aqueous systems. Furthermore, the effect of the catalytic hydrogenation of levulinic acid on the stability of the catalyst support is under investigation.

Current work is done by: Ernst.

The work focussed on polymers is done by: Ole and Shreshta.

In all the projects we can rely on the excellent support of our technicians: Hans, Ruud and Gerrit