University of St Andrews

Solar-driven water splitting or reduction of CO2 on photocatalysts represents one promising technique to convert solar energy into chemical energy. One current central task is to develop efficient solar-driven photocatalysts. The efficiency of photocatalysis is co-determined by three basic processes including light absorption, charge separation and catalytic conversion. Concerning these three basic processes, we focus on three strategies, 1) band engineering, 2) heterostructuring and 3) facet controlling, to tailor the properties of photocatalysts. The context of this talk mainly includes three parts, 1) the crucial role of spatial distribution of dopants or defects in realizing the redshift of the whole light absorption edge for a wide visible light absorption, 2) three kinds of core-shell engineered heterostructures with the ability of realizing spatial separation of photogenerated charge carriers, and 3) tailoring the exposure of different facets of photocatalysts.

Substitution of CC units by BN is an attractive means of changing electronic properties of molecules. A case in point is the relationship between benzene and its inorganic analogue borazine, sometimes termed “inorganic benzene.” One of our research projects in Tübingen focuses on the experimental realization of reactive intermediates that are boron-nitrogen analogues of conventional organic reactive intermediates. In the presentation our recent results on 1,2-azaborines, the BN derivatives of benzynes, and how that research led to the borazine derivative of hexa-peri-hexabenzocoronene (HBC), an iconic nanographene molecule, will be discussed.

Over the course of the last two decades, experiments with ultracold atoms and molecules have developed to a level where we have strongly interacting quantum gases that are controllable and measurable on a single-particle level. This now allows us to engineer a range of fundamental models from solid state physics in experiments, and explore their properties cleanly on a microscopic level.

Beyond textbook demonstrations of equilibrium and single-particle properties (including insulating phases, magnetic superexchange, and Bloch oscillations), this now enables us to explore fundamental aspects of non-equilibrium dynamics in quantum many-particle systems. These range from from the approach of systems to equilibrium, and thermalisation in statistical mechanics, to the influence of the environment and decoherence in open many-body quantum systems.

I will give an overview of recent developments in these areas, and touch on the recent measurement of many-body entanglement with ultracold atoms in optical lattices.

Metal organic frameworks (MOFs) represent tunable molecular scaffoldings that can be adjusted for a breadth of applications. This presentation will concern our efforts towards tailoring MOFs towards two globally relevant energy challenges, CO2 capture and fuel cells.

The first topic concerns our efforts to make MOFs for gas capture. Two sub-topics will be the use of MOFs with high CO2 capture ability and efforts to generally make MOFs more robust. In contrast to liquid amines which chemisorb CO2 and have high energy costs for regeneration, the MOF approach typically gives physisorbed gases and hence more facile release. Despite the weaker binding mode, we will show that high selectivities are possible owing to heats of adsorption over 40 kJ/mol1 and cooperativity between CO2 molecules in augmenting binding.2  Related to this is the need to enhance water stability of the MOF backbone and our efforts to achieve this goal will be presented.3

The second topic concerns an approach to better proton conductors for PEM fuel cell membranes.4 A major hurdle in these technologies is an electrolyte capable of operating above 100ËšC. Higher operating temperatures will enhance electrode kinetics and decrease electrode poisoning among several critical operational benefits. In contrast to polymer approaches towards these electrolytes, we have used a MOF strategy to generate crystalline networks with acidic pores. These MOFs present options for higher temperature conduction,5 conduction over 10-2 Scm-1,6 and water stability.7,8

[1] R. Vaidhyanathan et al. Science, 2010, 330, 650. [2] R. Vaidhyanathan et al. Angew. Chem., 2012, 51, 1826. [3] a) J. M. Taylor et al., J. Am. Chem. Soc. 2012, 134, 14338; b) Gelfand, B. S. Dalton Trans, in press.  [4] G. K. H. Shimizu et al. Science, 2013, 341, 354. [5] J. A. Hurd et al. Nature Chem. 2009, 1, 705. [6] S. Kim et al., J. Am. Chem. Soc. 2013, 135, 963.[7]J. M. Taylor et al., J. Am. Chem. Soc. 2013, 135, 1193. Ramaswamy, P. et al.J. Am. Chem. Soc. 2015, 137, 7640

There is currently great interest in the nature and reactivity of molecular uranium-ligand multiple bonds.1 This is because the nature and extent of 5f/6d orbital participation in uranium-ligand bonding is still a topic of debate, and the unique orbital-hybridisation patterns available to uranium promises novel reactivity and magnetism. We have found that certain triamidoamine ligands are exceptionally effective at stabilising unprecedented uranium-ligand multiple bonds involving main group fragments of interest in their own right. This talk will provide an overview of our progress to date covering oxo, nitride, parent-imido, -phosphinidene, -arsinidene, and arsendio complexes, and their electronic structure, bonding, reactivity, and magnetism will be discussed. If time allows we will describe our more recent work in this area.

We gratefully acknowledge continued and generous funding by the Royal Society, European Research Council, Engineering and Physical Sciences Research Council, The University of Nottingham, The University of Manchester, UK EPSRC National EPR Facility, COST, and the UK National Nuclear Laboratory.

1. S. T. Liddle, Angew. Chem. Int. Ed. 2015, 54, 8604.

The composition and spatial distribution of molecular gas in the inner few AU of young (< 10 Myr) circumstellar disks are important components to our understanding of the formation of planetary systems.  In the first part of this talk, I will discuss the current, observationally-based picture of protoplanetary gas disks at r < 10 AU.  I will review the most widely used spectral diagnostics of the inner disk, and highlight recent observations of H2 and CO made by the Hubble Space Telescope.  I will describe how high-resolution spectroscopy is being used to constrain the composition, distribution, and evolution of molecular gas in the inner disk at spatial scales too small to resolve with current imaging instruments/facilities.  

In the second part of this talk, I will discuss how the spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres.  I will present results from a Hubble Treasury program that is currently underway to characterize the panchromatic (X-ray through mid-IR) radiation environments around low-mass host stars for the first time.   We find that all exoplanet host stars observed to date exhibit significant levels of UV/X-ray activity, and that strong flares are common, even on “optically inactive” M dwarfs hosting planetary systems.  I will briefly discuss the use of these data in atmospheric models of rocky planets around cool stars, including the predicted abiotic production of O2 and O3 – a cautionary tale for the interpretation of “biomarker” gases when they are detected in the coming decades.