Diamond Concise Annual Review 2021/22

24 25 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 Crystallography Group T he Crystallography Group comprises the High-Resolution Powder Diffraction beamline (I11), the Extreme Conditions beamline (I15), the X-ray Pair Distribution Function (XPDF) beamline (I15-1), and the Small-Molecule Single-Crystal Diffraction beamline (I19). Having these beamlines together in one science group allows us to fully exploit the technical and scientific expertise within its teams to provide the basis for future development and pioneering experiments. The Group’s beamlines use various techniques to study structural properties of crystalline, amorphous, and liquidmaterials indifferent conditions. These powerful facilities are used in awide range of science disciplines, including CondensedMatter Physics, Chemistry, Engineering, Earth andMaterials, and Life Sciences. Studies in the past year have included improving effectiveness of photocatalysts, developing new battery materials andmolecular knotting technologies. Improving the efficiency of photocatalysts in water splitting Materials containing titanium dioxide (TiO 2 ) powder have been widely studied as efficient photocatalysts for splitting water into its constituent parts and are used in many technological applications such as fuel cells, solar energy production, and catalysis. Their benefits include low cost, photo-responsivity, earthly abundance, and chemical/thermal stability. The recent breakthrough of nitrogen-doped TiO 2 shows an impressive visible-light absorption for photocatalytic activity. Although their electronic and optical properties have been extensively studied, the structure-activity relationship and photocatalytic mechanism remain ambiguous. Researchers from the University of Oxford performed structural characterisation of nitrogen-doped TiO 2 using X-ray powder diffraction with data collected at beamline I11. They identified a new cubic titanium oxynitride phase for highly-doped anatase TiO 2 , which provides important information on the fundamental shift in absorption wavelength, leading to excellent photocatalysis using visible light. These results show that visible light can drive efficient photocatalytic water-splitting over nitrogen-doped TiO 2 , yielding plentiful hydrogen gas at elevated temperatures. Crucially, the absorption profile is shifted to longer wavelengths relative to undoped TiO 2 , which absorbs primarily in the ultraviolet region. Strong absorption of visible light enables more complete and effective use of the solar spectrum. Foo C et al. DOI: 10.1038/s41467-021-20977-z Developing newmaterials for electric car batteries The demand for lithium-ion batteries in the automotive industry is increasing rapidly and new generation batteries using affordable materials are urgently needed. A class of transition metal oxides are cost-effective candidates for electrodes but there has been limited understanding of how these materials change during battery cycling. Researchers from the University of Oxford used beamline I15-1 to characterise the nanoscopic phases present in the battery materials. The beamline’s high flux and high energy X-rays, together with its optimised in operando electrochemistry setup, allowed the researchers to collect high- quality pair distribution function data. This was crucial for investigating any nanostructured components and their phase behaviours in real time. Results of the study provided new mechanistic understanding of how these materials react and showed the origin of their slow electrochemical performance, providing new insights into effective strategies for further development. In addition, the study reported the experimental observation of the non-equilibriummetal monoxide polymorphs for the first time. This opens exciting new avenues for electrochemically-assisted synthesis to explore non- native metal oxides with new functionalities. Hua X et al. DOI: 10.1038/s41467-020- 20736-6 Designing newmaterials withmolecular knots Knots have been used for thousands of years to create tools and materials. They also play an important role at the nanoscale and are found in DNA and proteins, where they profoundly impact their stability and biological activity. Synthetic polymer chains also spontaneously tie into knots with the resulting effect determining macroscopic material properties such as stiffness and viscosity. The ability to knot molecular-sized threads, approximately 100,000 times thinner than a human hair, could make incredibly strong novel materials. These knots have unique molecular structures that have already been shown to catalyse chemical reactions, act as sequestering agents and kill cancer cells. However, methods of knotting such small threads are lacking, so researchers from the University of Manchester have developed a new technique for weaving at the molecular scale. They identified a suitable template that could control the weaving process by guiding the strands into a grid structure and used single crystal X-ray diffraction on beamline I19 to probe the relative positions of molecular strands. This research provides new understanding of the value of molecular knotting and new strategies to develop molecular knotted materials. Leigh DA et al. DOI: 10.1038/s41557-020-00594-x