Publication News

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29th November 2018

Interfaces Between Graphene‐Related Materials and MAPbI3: Insights from First‐Principles 

George Volonakis and Feliciano Giustino  from the Materials Modelling and Design Group report in Advanced Materials Interfaces the latest advances on the computational exploration of the interactions between graphene and graphene oxide with lead halide perovskites. They also show how recent calculations from first principles have been employed towards understanding the benefits of combining these ‘wonder materials’.  The paper was selected as cover image of the special section on "Interfacial engineering of perovskite solar cells for improved performance and stability".  

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26th November 2018

Tailored homo- and hetero- lanthanide porphyrin dimers: a synthetic strategy for integrating multiple spintronic functionalities into a single molecule

Jennifer Le Roy's recent publication in Chemical Science has been selected as front cover article and classed as a hot article. Researchers from Professor Bogani's group in Materials in collaboration with researchers from Professor Anderson's group in Chemistry report the design, synthesis and magnetic properties of molecular magnetic systems that contain all elements necessary for spin-valve control in molecular spintronic devices in a single molecule.

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16th November 2018

Low Cost, Robust, Environmentally Friendly Geopolymer–Mesoporous Carbon Composites for Efficient Solar Powered Steam Generation

Professor Bob Bradley and his company Matsurf Technology UK Ltd. has recently published in the Journal of Advanced Functional Materials work on a new solar powered desalination unit. The device, which is free-floating, uses a solar-capture layer produced from a biowaste derived mesoporous carbon (BMC) supported on a capillary geopolymer and has one of the highest saline to steam conversion rates ever reported (7.55 kg m−2 h−1).

 

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14th November 2018

Low-Dose Aberration-Free Imaging of Li-Rich Cathode Materials

Research by the Peter Bruce Group and collaborators at the Department of Materials as reported in Nano Letters provides an insight to the atomic structure of cathode materials. Imaging the complete atomic structure of materials, including light elements, with minimal beam-induced damage of the sample is a long-standing challenge in electron microscopy. Annular bright-field scanning transmission electron microscopy is often used to image elements with low atomic numbers, but due to its low efficiency and high sensitivity to precise imaging parameters it comes at the price of potentially significant beam damage. In this work they showed that electron ptychography is a powerful technique to retrieve reconstructed phase images that provide the full structure of beam-sensitive materials containing light and heavy elements. Due to its much higher efficiency, beam currents used were reduced down to the subpicoampere range. Electron ptychography also allows residual lens aberrations to be corrected at the postprocessing stage, which avoids the need for fine-tuning of the probe that would result in further beam damage and provides aberration-free reconstructed phase images. Electron ptychography obtains structural information from aberration-free reconstructed phase images in the technologically relevant lithium-rich transition metal oxides at different states of charge. The technique allows to determine the position of the lithium and oxygen atomic columns while amorphization of the surface, formation of beam-induced surface reconstruction layers, or migration of transition metals to the alkali layers are drastically reduced.

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3rd August 2018

Degradation Mechanisms in an All-Solid-State Lithium-Ion Battery

Research by the Peter Bruce Group and collaborators at University of Giessen as reported in ACS Applied Materials & Interfaces provides an insight to the degradation mechanism in an All-Solid-State Lithium-Ion Battery. All-solid-state batteries (ASSBs) show great potential for providing high power and energy densities with enhanced battery safety. While new solid electrolytes (SEs) have been developed with high enough ionic conductivities, SSBs with long operational life are still rarely reported. Therefore, on the way to high-performance and long-life ASSBs, a better understanding of the complex degradation mechanisms, occurring at the electrode/electrolyte interfaces is pivotal. While the lithium metal/solid electrolyte interface is receiving considerable attention due to the quest for high energy density, the interface between the active material and solid electrolyte particles within the composite cathode is arguably the most difficult to solve and study. In this work, multiple characterization methods are combined to better understand the processes that occur at the LiCoO2 cathode and the Li10GeP2S12 solid electrolyte interface. Indium and Li4Ti5O12 are used as anode materials to avoid the instability problems associated with Li-metal anodes. Capacity fading and increased impedances are observed during long-term cycling. Postmortem analysis with scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy show that electrochemically driven mechanical failure and degradation at the cathode/solid electrolyte interface contribute to the increase in internal resistance and the resulting capacity fading. These results suggest that the development of electrochemically more stable SEs and the engineering of cathode/SE interfaces are crucial for achieving reliable SSB performance.

Device logic

16th July 2018

Device-level photonic memories and logic applications using phase-change materials

Photonics is believed to be one of the best candidates for a future computing system, which can perform data storage and processing in an optical manner at extremely high speed and with unprecedented bandwidth. However, it’s essential yet difficult to build the electronic counterparts, such as non-volatile memories and logic devices, in optical manner. Researchers from the Advanced Nanoscale Engineering group, collaborated with University of Exeter (UK), University of Muenster (Germany) and Massachusetts Institute of Technology (USA) reported their latest results on integrated photonic memories and logic devices based on phase-change materials in Advanced Materials. Phase-change materials (PCMs), widely used in rewritable optical discs and phase-change memory applications, show a substantial difference in both electronic and optical properties between the amorphous and crystalline states. In photonic memory implementations, the authors developed an optical pulse width modulation (PWM) technic, successfully achieving multi-level and non-volatile photonic memories with complete random accessibility. Furthermore, they demonstrated programmable optical logic devices with logic “OR” and “NAND” achieved on just a single photonic memory device. Their study provides a practical and elegant technique to optically program multiple functions in photonic phase-change devices for future computing applications.

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23rd June 2018

Halide double perovskites for water splitting

Since their discovery in 2016, halide double perovskites that are based on combinations of monovalent and trivalent cations, have been thoroughly investigated as potential lead-free alternatives to lead halide perovskites. In a recent study published in Applied Physics Letters,  researchers George Volonakis and Feliciano Giustino, considered applications beyond photovoltaics and found that the lead-free double perovskites Cs2BiAgCl6, Cs2BiAgBr6, Cs2SbAgCl6 and Cs2InAgCl6 may open new opportunities in solar-driven photocatalytic water splitting. Using first-principles calculations they report on the stability of different surface terminations of the newly synthesised double perovskites, and also report their absolute energy levels. The energy levels of Cs2BiAgCl6 and Cs2BiAgBr6 are matching the redox potential of water. While, Cs2SbAgCl6 and Cs2InAgCl6 could also be suitable for either hydrogen evolution or water evolution. Futher details are in the AIP journal feature article press release.

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22nd June 2018

Maximising the resolving power of the scanning tunneling microscope

Research by the Surface Nanoscience group and collaborators at Trinity College Dublin as reported in open access Advanced Structural and Chemical Imaging demonstrates that a significant improvement in the resolving power of the STM is achieved through automated distortion correction and multi-frame averaging. We demonstrate the approximately square-root relationship improvement in signal-to-noise ratio upon image averaging, a sub-picometre precision height measurement, and the automated identification of chiral unit cells on a surface. These automated tools, which do not require prior knowledge of the surface structure, promise to facilitate more rapid and higher-precision studies of surfaces, making full use of the experimentalists recorded data sets. This advance allows a new study of surface pico-science to be developed where subtle variations in surface structure can now be seen, that hitherto were not detected because they were buried in noise.

Electrical percolation through a discontinuous Au nanoparticle film

21st June 2018

Electrical percolation through a discontinuous Au nanoparticle film

Researchers in the Surface Nanoscience Group report in Applied Physics Letters evidence of stepwise control of resistivity in thin gold layers. When a thin gold film is deposited the electrical resistance of the film decreases from fully resistive at the start of deposition to close to the bulk resistance for thicker films. We’ve found that, instead of a smooth decrease, this resistance change occurs in discrete steps. The steps are attributed to conduction through newly formed electrical pathways in the discontinuous film being created as more gold is deposited. Scanning electron microscopy images confirm the discontinuous nature of the films and show that thicker layers are more connected. Annealing such films causes them to dewet, decreasing the number of conductive pathways and causing a stepwise increase in the resistance of the film. This control over the electrical resistance of the layer as well as the size and separation of the particles opens up new opportunities for various applications of discontinuous metal films.

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15th June 2018

Improving the specific energy of the Li-ion battery with new cathode material

Research by the Peter Bruce Group and collaborators at Japan Synchrotron Radiation Research Institute (JASRI) and Uppsala University as reported in Energy & Environmental Science explains that the greatest barrier to improving the specific energy of the Li-ion battery is the cathode. While Si offers a route to increase the capacity at the anode this needs to be balanced by higher energy storage cathodes. The capacity of the cathode is limited by storing electrons on the transition metal ions alone, such as in LiMn2O4, where electrons are stored on the Mn 3+/4+ redox couple. There is a great deal of interest in increasing charge storage in transition metal oxide cathodes beyond the limit of transition metal redox activity. While redox reactions on sulfur in transition metal sulfides are well known only recently has O redox activity in transition metal oxides been recognised. They report a new intercalation cathode material, a lithium manganese oxyfluoride based on Li2MnO2F, with a high capacity to store charge by invoking redox activity on the Mn cations and O anions. It has a disordered rocksalt structure, which avoids the structural changes and consequent severe changes in voltage observed for O-redox layered transition metal oxide cathodes during the 1st cycle.

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