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Abstract: We studied the structural and electronic properties of 2,3,9,10-tetrafluoropentacene (F4PEN) on Ag(111) via X-ray standing waves (XSW), low-energy electron diffraction (LEED) as well as ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS). XSW revealed that the adsorption distances of F4PEN in (sub)monolayers on Ag(111) were 3.00 Å for carbon atoms and 3.05 Å for fluorine atoms. The F4PEN monolayer was essentially lying on Ag(111), and multilayers adopted π-stacking. Our study shed light not only on the F4PEN–Ag(111) interface but also on the fundamental adsorption behavior of fluorinated pentacene derivatives on metals in the context of interface energetics and growth mode.

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Abstract: Materials that display strong capabilities for lithium insertion without significant change in unit cell size on cycling are of considerable importance for electrochemical applications. Here, we present V2O3(SO4)2 as a host for lithium-ion batteries. Electrochemically, 2.0 Li+ ions can be inserted, giving Li2V2O3(SO4)2 with an oxidation state of V4+, as determined by X-ray absorption spectroscopy. The capacity of V2O3(SO4)2 can be increased from 157 mA h g−1 to 313 mA h g−1 with the insertion of two additional Li+ ions which would drastically improve the energy density of this material, but this would be over a wider potential range. Chemical lithiation using n-butyllithium was performed and characterisation using a range of techniques showed that a composition of Li4V2O3(SO4)2 can be obtained with an oxidation state of V3+. Structural studies of the lithiated materials by X-ray diffraction showed that up to 4.0 Li+ ions can be inserted into V2O3(SO4)2 whilst maintaining its framework structure.

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Abstract: Cooking emissions account for a significant proportion of the organic aerosol emitted into the urban environment and high pollution events have been linked to an increased organic content on urban particulate matter surfaces. We present a kinetic study on surface coatings of self-assembled (semi-solid) oleic acid-sodium oleate cooking aerosol proxies undergoing ozonolysis. We found a clear film thickness-dependent kinetic behaviour and measured the effect of the organic phase on the kinetics for this system. In addition to the thickness-dependent kinetics, we show that significant fractions of unreacted proxy remain at the end of extensive ozone exposure and that this effect scales approximately linearly with film thickness, suggesting that a late-stage inert reaction product may form to inhibit reaction progress – effectively building up an inert crust. We determine this by using a range of simultaneous analytical techniques; most notably Small-Angle X-ray Scattering (SAXS) has been used for the first time to measure reaction kinetics of films of a wide range of thicknesses from ca. 0.59 to 73 µm with films < 10 µm thick being of potential atmospheric relevance. These observations have implications for the evolution of particulate matter in the urban environment, potentially extending the atmospheric lifetimes of harmful aerosol components and affecting the local urban air quality and climate.

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Abstract: Cu2O is an attractive photocathode for important renewable energy reactions such as water splitting and CO2 reduction. Electrodeposition is commonly used to deposit Cu2O films on conductive substrates due to its simplicity and consistency. However, structural descriptors, linking electrodeposition parameters, film structure and the catalytic properties are elusive. A variety of Cu2O films reported by many research groups would often display vastly different electronic properties and catalytic activity, while appear indistinguishable under common characterisation tools. In this work, we take a systematic look into electrochemically deposited Cu2O and investigate the impact of deposition parameters towards the bulk and surface chemistry of the deposited film. Specifically, we employ high resolution XANES for thorough quantitative analysis of the Cu2O films, alongside more common characterisation methods like XRD, SEM and Raman spectroscopy. Photoelectrochemical (PEC) studies reveal an unexpected trend, where the highest PEC activity appears to correlate with the amount of Cu2+ content. Other factors which also affect the PEC activity and stability are film thickness and crystallite grain size. Our study shows that the use of high resolution XANES, though not perfect due to possible self-absorption issue, is apt for extracting compositional descriptor in concentrated thin film samples from the pre-edge energy position analysis. This descriptor can serve as a guide for future development of more active Cu2O based films for wide range of PEC processes as well as for solar cell applications.

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Abstract: The assembly of a septin filament requires that homologous monomers must distinguish between one another in establishing appropriate interfaces with their neighbors. To understand this phenomenon at the molecular level, we present the first four crystal structures of heterodimeric septin complexes. We describe in detail the two distinct types of G-interface present within the octameric particles which must polymerize to form filaments. These are formed between SEPT2 and SEPT6 and between SEPT7 and SEPT3, and their description permits an understanding of the structural basis for the selectivity necessary for correct filament assembly. By replacing SEPT6 by SEPT8 or SEPT11, it is possible to rationalize Kinoshita's postulate which predicts the exchangeability of septins from within a subgroup. Switches I and II, which in classical small GTPases provide a mechanism for nucleotide-dependent conformational change, have been repurposed in septins to play a fundamental role in molecular recognition. Specifically, it is switch I which holds the key to discriminating between the two different G-interfaces. Moreover, residues which are characteristic for a given subgroup play subtle, but pivotal, roles in guaranteeing that the correct interfaces are formed.