In the early 1900s the idea of compounds with silicon-silicon double bonds was conceived by F.S. Kipping and publicised with the report on what we now call a disilene. While this compound later turned out to be a saturated species, this article marked the birth of organosilicon chemistry. It took until the 1980s before a genuine stable disilene was reported thus enabling thorough investigations into such compounds. Despite this late breakthrough, the quest for silicon double bonds was marked by major milestones, e.g. semiconducting polysilanes. The most prominent spin-out from the hunt for unsaturated silicon species is, however, the area of silicones (robust, still extremely flexible coatings, lubricants, plastics, etc.), which has its origins in Kipping's misconception that he had synthesised a silicon analogue of organic ketones - a silicone .An important motivating force in disilene chemistry is the resemblance of the Si=Si bond to the so-called buckled dimer terminating the surface of elemental silicon, which is used for the majority of applications of this archetypical semiconductor. The shallow potential energy surface and the resulting conformational flexibility of the Si=Si bond renders even topologically different disilenes suitable as models for the silicon surface. Disilenes replicate the weak pi-bond inherent to the buckled dimer with the small HOMO-LUMO gap and high reactivity. The application of Si=Si moieties as functional units in molecules and materials, however, remained unexplored even though such an endeavour would literally marry the concepts of classical semiconductors with that of the newly emerging organic electronics. The reason for this is readily identified in the absence of functional disilenes in the toolbox of the preparative silicon chemist. Unlike in the case of the ubiquitous alkenes that are mainly responsible for the vast diversity of Organic Chemistry, functional disilenes capable of transferring the Si=Si moiety only became readily available in 2004 by our efforts.This synthetic project will further develop the chemistry of functional disilenes. The so far most versatile transfer reagents for Si=Si moities are nucleophilic disilenides. Alternative reagents with modified reduction potential are needed to broaden their scope towards redox sensitive substrates. Electrophilic counterparts that reverse the polarity of disilenides are going to be prepared and provide access to compound classes where only nucleophilic substrates are available and/or safe to handle. After initial successes regarding the incorporation of Si=Si moieties to the periphery of pi-conjugated organic systems using disilenides, it also became quickly apparent to us that a further development of this emerging field urgently requires di- or polyfunctional derivatives, which would open the door to various applications towards supramolecular chemistry, polymer chemistry, and surface chemistry to name only a few. Our inherently molecular approach will allow us an unprecedented level of control over atomic subunits of classical semiconductors and their incorporation into organic electronics. The synthesis of a number of di- and trifunctional derivatives based on various pi-conjugated organic scaffolds will thus be pursued. To this end, conceptually novel methodologies will be developed including the use of protecting groups to carry masked functionalities through the entire length of synthetic procedures. The reactivity of these new compounds with multiple functional Si=Si moieties will be screened in comparison with that of simple disilenides.To summarise, this project will be at the forefront of the newly emerging field of an application- and property-driven chemistry of the Si=Si double bond. It will provide the synthetic tools that are ultimately expected to enable us to utilise the unique physical and chemical properties of disilenes in various applications of nanoscalar electronics.

Flows of complex fluids (such as polymers, colloids, emulsions, pastes etc.) are abundant in everyday life. One can think of pouring syrup from a bottle or squeezing toothpaste from a tube, but also of fibre-spinning and extrusion - processes used to produce plastic bags, optical fibres, wire coatings, guitar strings etc. Complex fluids, and polymer solutions in particular, often exhibit unexpected behaviour - they do not flow like water. For example, if one rotates a spoon in a cup of tea, the tea is pushed towards the walls of the cup. When, instead, this experiment is repeated with a polymeric liquid, the polymers move towards the spoon producing the so-called rod-climbing effect.What is even more surprising is that flows of polymers can become unstable. One of the famous examples is the melt-fracture phenomenon observed in extrusion of concentrated polymer solutions or melts, which is one of the main elements of polymer processing in industry. There the liquid is pressed through a thin capillary to produce a regular jet of polymers. At low extrusion speeds the jet remains straight and homogeneous, while at larger speeds the flow starts undulating, becomes chaotic and eventually breaks up. These instabilities are one of the main production-limiting factors and have been plaguing technology and industry for years. Their presence is surprising since in Newtonian flows, instabilities and the transition to turbulence are inertia-driven, and are expected to occur when the Reynolds number exceeds some critical value. The Reynolds number characterises the ratio of inertial to viscous effects and is inversely proportional to the fluid viscosity. For extremely viscous polymeric fluids typical Reynolds numbers are very small, far below the critical value. The inertia-driven transition is thus absent and can not explain instabilities in polymeric solutions. Instead, some other mechanism causes destabilisation.The striking properties of polymer solutions and melts arise from the interactions between their microstructure and the flow: long polymer molecules are stretched and oriented by the flow. In the past 20 years, we have begun to understand that flow-induced stretching and orientation of polymers can not only make polymers flow differently than water, but can also destabilise the flow, leading to vortices and random flows. This chaotic motion looks similar to Newtonian turbulence but is not inertial in origin. This new type of turbulence, the so-called elastic turbulence, is poorly understood and little is known about its structure and conditions at which it might appear.The aim of this research programme is to study this new type of turbulence by means of computer simulations and semi-analytical methods recently developed to describe the structure of Newtonian turbulence close to the transition. The motivation to perform this study is three-fold. First, this is a completely new type of turbulence which we have not encountered in Newtonian fluids like water. Since many every-day fluids are non-Newtonian and viscoelastic, it might be that understanding elastic turbulence is even more important than understanding Newtonian one. Secondly, understanding the origin of elastic turbulence might provide a solution to the industrial problems like melt-fracture. Finally, by comparing the two, we may learn something about the mechanism of Newtonian turbulence.

The capture and management of ions in water systems are of widespread importance to society. One of the most prominent applications is water desalination, which is becoming an increasingly important technology due to population growth and climate change putting pressure on freshwater resources. In recent years, capacitive de-ionisation (CDI) has gained increasing attention as a potentially low-energy alternative to more common desalination methods such as reverse osmosis. CDI works by passing a saline solution through an electrochemical cell where the positive and negative salt ions are immobilized on the surfaces of oppositely-charged porous carbon electrodes. One of the advantages of CDI over other desalination methods is that following the initial ion capture step, the electrode can be regenerated by discharging into a separate effluent stock. In this step, some of the energy used for the ion capture is recovered, and furthermore, the efficient regeneration of the electrode reduces fouling. Despite the promise of CDI, its efficiency reduces at high salt concentrations. In this respect, it does not compete with other methods such as reverse osmosis for treatment of seawater. In recent years there have been considerable research efforts to extend the concentration range in which CDI is effective. Most development has focused on optimisation of materials and cell designs with considerable success, yet, surprisingly little consideration has been given to details of the the ion behaviour or the elementary processes taking place at each electrode. One of the primary considerations is to ensure that ionic charge is stored by ions being captured by the electrode, rather than being exchanged with those in the feed electrolyte (which does not reduce the salt concentration). This proposal seeks to develop a mechanistic understanding of CDI and apply this knowledge to control the ion storage mechanism to optimize the salt removal efficiency. This will be done through the use of detailed electrochemical analysis and the use of nuclear magnetic resonance (NMR), which allows us to "see" and count ions that are captured in the electrode, and correlate this with the electrochemical response and salt removal efficiency. We will investigate how the electrode pore size and electrolyte properties, such as concentration and the nature of the ions present, affect how they are captured. This information will then be used to inform and optimise the cell design and operational conditions (e.g., flow rate and cell voltage). Our proposed work is necessarily fundamental in nature with the key aim of improving the understanding of the underlying science of CDI, rather than fabrication of prototype CDI stacks. However, through our collaborations with academic and industrial partners, we aim to work with, and identify, scalable and commercially-relevant electrode materials.

Silicon based information technology has revolutionized the modern world. As device features have decreased in size, integrated circuits (ICs) have become subject to quantum mechanical phenomena. Quantum technologies aim to exploit these quantum mechanical phenomena to perform tasks that are difficult or impossible with conventional technologies. One of the main obstacles in developing quantum technologies is the rapid destruction of quantum superposition states caused by interference with the environment in a process called decoherence. Recently, extremely long coherence times (hours) have been demonstrated using small amounts of additives to silicon that have a "spare" electron (donor impurities). Although even longer times can be obtained for atoms in vacuum, an atom trapped permanently in a solid crystal such as silicon is much easier to handle. A major source of decoherence in solids is the nuclear spin of the atoms that make up the host crystals, as they often flop around uncontrollably. This has been eliminated by isotopically purifying the silicon (which normally contains a mix of isotopes, only a small number of which have nuclear spin). Even so, the donor impurities don't interact with telecoms wavelength light, and this is critical for many quantum technologies, quantum communication schemes in particular. There are currently no solid-state quantum technology platforms with long coherence times and optical fibre telecommunications compatibility. The optical transitions of the rare-earth atom erbium are, however, telecommunications compatible. Rare-earth ions are also ideal systems for quantum technologies because the shielding of their electrons offers an atomic scale barrier to decoherence. When doped into relatively high nuclear spin metal oxide crystals, rare-earths show coherence times comparable to donor impurities in natural silicon, but are yet to be investigated in silicon themselves. Ion implantation is a well understood technology used in today's silicon IC manufacture and history has shown that commercial interest in new technologies favours those relying on established fabrication platforms and techniques. Given the expected improvement in coherence time from using erbium implanted isotopically pure silicon, it should be possible to develop a quantum technology platform that has a long coherence time, and is telecommunications and conventional IC tooling compatible. Quantum computation schemes require the entanglement of quantum bits (qubits), this remains challenging in silicon based qubits but has been demonstrated in superconducting circuit qubits. As the latter has short coherence times and lacks optical addressability, I envisage a hybrid scheme where processing is performed with the superconducting resonators and erbium implanted silicon qubits are used as the quantum memory element and as a quantum transducer between telecommunications and microwave wavelength photons. Through this project I will introduce a new quantum technology platform to the research community: erbium implanted silicon. This platform combines the telecommunication capability of erbium and integrated circuit capability of silicon, making it valuable for both quantum computing and quantum communication applications.

Recent progress in various areas of physics has demonstrated our ability to control quantum effects in customized systems and materials, thus paving the way for a promising future for quantum technologies. The emergence of such quantum devices, however, requires one to understand fundamental problems in non-equilibrium statistical physics, which can pave the way towards full control of quantum systems, thus reinforcing new applications and providing innovative perspectives. This project is dedicated to the study and the control of out-of-equilibrium properties of quantum many-body systems which are driven across phase transitions. Among several approaches, it will mainly focus on slow quenches and draw on the understanding delivered by the Kibble-Zurek (KZ) mechanism. This rather simple paradigm connects equilibrium with out-of-equilibrium properties and constitutes a benchmark for scaling hypothesis. It could pave the way towards tackling relevant open questions, which lie at the heart of our understanding of out-of-equilibrium dynamics and are key issues for operating in a robust way any quantum simulator. Starting from this motivation, we will test the limits of validity of the KZ dynamics by analyzing its predictions, thus clarifying its predictive power, and extend this paradigm to quantum critical systems with long-range interactions and to topological phase transitions. We will combine innovative theoretical ideas of condensed-matter physics, quantum optics, statistical physics and quantum information, with advanced experiments with ultracold atomic quantum gases. Quantum gases are a unique platform for providing model systems with the level of flexibility and control necessary for our ambitious goal. Their cleanness and their robustness to decoherence will greatly enhance the efficient interplay between theory and experiments, and provide a platform of studies whose outcomes are expected to have a strong scientific impact over a wide range of disciplines. On the short time scale we will exploit this knowledge to develop viable protocols for quantum simulators. In general, we expect that the results of this project will lay the ground for the development of the next generation of quantum devices and simulators.