MRI: Acquisition of a single crystal x-ray diffractometer at UC Merced

This award is jointly supported by the Major Research Instrumentation and the Chemistry Research Instrumentation Programs. The University of California - Merced is acquiring a dual-source single crystal diffractometer equipped with Cu and Mo microfocus X-ray sources, Professor Michael Findlater and colleagues Rebeca Arevalo, Mehmet Baykara, Jennifer Lu, Yanbao Ma.

In general, an X-ray diffractometer allows accurate and precise measurements of the full three-dimensional structure of a molecule, including bond distances and angles, and provides accurate information about the spatial arrangement of a molecule relative to neighboring molecules. The studies described here impact many areas, including organic and inorganic chemistry, quantum materials, materials chemistry, biochemistry, and catalysis.

This instrument is an integral part of teaching as well as research and research training of undergraduate and graduate students in chemistry and biochemistry at this institution. The facility serves as a regional XRD resource benefitting students and faculty from primarily undergraduate institutions within the Central Valley region of California with impacts through active collaborations with researchers California Polytechnic State University, CSU Sate East Bay, CSU State Stanislaus, and Western Oregon University.

The award is aimed at enhancing research and education at all levels. Research enabled by the instrument is focused on the synthesis, isolation, characterization, and reactivity of molecular compounds with 1st-row metal elements which exhibit such redox behaviors. The identification of novel structure and bonding has long been a central tenet of molecular inorganic / organometallic chemistry, and SCXRD is an essential characterization tool.

More efficient access to crystallographic data helps streamline the development of structural analogues and guide the design of future structural modifications based on rotamer assessment. This is needed of the development of transnitrosylation reactions from novel nitrosoreagents. X-ray crystallography has become much more than a tool for structure determination - it is a technique that allows the exploration of the conformational landscapes of complex molecules in atomic detail.

The instrument helps develop new computational tools that enable "multi-conformer" or "ensemble" modeling of crystallographic data, revealing hidden alternative conformations of macromolecules, which is often critical for understanding their functions. Researchers are working on single crystal selection and manipulation for the SCXRD. For material and chemical applications, dry crystal specimen is commonly used in the SCXRD.

For biochemical and biological applications, the specimen may stay in aqueous solutions during the SC-XRD measurements. Depending on different applications, either acoustic or optical tweezers are utilized. Water electrolysis is a viable option towards hydrogen production that facilitates the transition into a decarbonized economy.

The structures and purity of catalytic materials are Confirmed by XRD results. The discovery that the structure of 2D materials used as solid lubricants has a profound effect on their frictional properties. In particular, MoS2 doped with Re ions exhibits an anomalous, i.e. inverse dependence of friction on number of layers in violation of the seemingly universal trait that friction decreases with increasing number of layers in 2D materials.

Structure determination using the instrument is of prime importance for friction research. SCXRD is an essential characterization tool for identifying new phases and structures of quantum materials. SCXRD is used to identify the crystal structure of the synthesized quantum materials and study the evolution of their lattice and phase upon the introduction of heterogeneities.

Metal halide perovskites (MHPs) have had a meteoric rise in the last decade as active materials in high-efficiency single junction solar cells. The first and most critical step following synthesis of these materials is SCXRD to ascertain lattice constants and crystal orientation of the MHPS. Without this characterization, any measurement done on these samples have retain considerable uncertainty and do not allow to establish the correlations between composition and optoelectronic behavior.

Metal organic frameworks (MOFs), consisting of metal ions and their interlinking organic ligands, can be formed into a highly crystalline porous structure with excellent tunability in both morphology and functionality, which provides an attractive platform to explore unprecedented catalytic activity and selectivity. Characterization of these materials with SCXRD allow understanding where the catalytically active sites are located and how the electrocatalysis occurred on those sites.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.