High surface area nanoporous films formed by sintering metal oxide nanoparticles are highly stable, non-toxic and inexpensive to produce on an industrial scale. They find a wide range of applications in gas sensing and catalysis where high surface area is essential to maximise the interaction of molecules with the film. They also find applications as charge transport layers in third generation solar cells, e.g. dye- or perovskite-sensitised cells, where efficient photoinjection of electrons and holes is ensured by coating nanoporous films with a light absorbing material. For solar cells, as well as for other important applications of nanoporous films such as electrodes in fuel cells and photoelectrochemical cells, good charge carrier mobility is also an essential requirement. Unfortunately, despite their numerous advantages, the electronic mobility of nanoporous oxide films is in general very poor. For example, the mobilities of nanoporous TiO2, ZnO and SnO2 films have been shown to be between two and four orders of magnitude smaller than those of corresponding single crystals. This low mobility is a key factor limiting the efficiency of (photo-)electrochemical and photovoltaic applications and is usually attributed to increased charge carrier trapping at surfaces and at interfaces between nanoparticles. Since charge trapping is associated with ions near surfaces we hypothesise that it should be possible to eliminate these traps by suitable chemical modification of the surfaces of nanoparticles prior to sintering into a film. This approach would retain the advantages of nanoporous films in terms of high surface area, non-toxicity and processability while improving mobility. Such modifications have been attempted previously, but due to the lack of understanding on the origin of charge trapping or the effects of surface modification, success has been limited. Here, we propose to combine the predictive power of first principles theoretical modelling with structural, spectroscopic and photophysical materials characterisation, in order to quantify the factors responsible for charge trapping at surface and interfaces in nanoporous oxide films at an atomistic level. Once validated and refined on unmodified films, theoretical methods will be used to assess modification strategies to reduce charge-trapping. In particular, we will consider the incorporation/substitution of anions and cations near the surface of oxide nanoparticles to eliminate the problematic trapping sites. The ability to theoretically screen various possible modification routes (i.e. different cations and anions) is a key advantage of our proposed approach. Application, testing and optimisation of such strategies may offer a new paradigm for knowledge-led design of solar oxide materials. We aim to demonstrate the effectiveness of our approach by increasing the mobility of nanostructured TiO2 and ZrO2 to deliver an improvement in the efficiency of perovskite-sensitised solar cells, which are emerging as an attractive third generation photovoltaic technology. The size of the third generation photovoltaic market is predicted to grow to $38bn by 2022, making this an area with significant potential for economic impact. Improving the mobility of nanoporous oxides could bring the efficiency of these devices from their current level (about 20%) to closer to the theoretical maximum of about 30%. An increase in overall efficiency from 20% to only 23% percent would increase the total power output by 15%, which when coupled with lower manufacturing costs would make the technology very attractive. We will work with leading manufacturers of nano-TiO2 (Cristal) and perovskite-sensitised solar cells (Dyesol Limited) to test the performance of our modified films. More generally, the ability to tailor the electronic properties of interfaces in nanoporous films by controlled modification should find applications in other technologies including sensing, catalysis and electronics.

Atomistic structural, electronic and chemical models are the basis of modern material science, with data acquired under regular high vacuum conditions by analysis of mainly static specimens. However, the properties and hence functionality of many materials crucially depend on the environmental conditions to which they are exposed. Accordingly, relevant analyses of structure, composition and properties need to be conducted under controlled continuous dynamic conditions and the vision of this project is to enable and fully integrate the capabilities needed to accomplish these goals to understand nanomaterial-environment interactions, and ultimately to create nanomaterials by design. The overarching vision of this proposal is to fill the need for the fully integrated nanomaterials analysis with single atom sensitivity under dynamic process conditions in environmental conditions. The aim is to provide the state of the art tool available to UK research community to address the outstanding materials problems that underpin a number of EPSRC research themes from manufacturing the future to health and environment. Fully in situ and operando operations are needed to ensure the integrity of sample data. In practice this extends from sample synthesis or activation, through the ensuing operations, reactions or other processes or tests. Hence, resources are sought to establish a state-of-the-art, aberration corrected STEM instrument (200 to 40 kV) with 0.08 nm image resolution and comprehensive analytical functions for chemical and electronic state analysis with electron energy loss spectroscopy (EELS), related imaging filter (GIF), direct electron detection, and elemental analysis with a transformational high sensitivity (and acceptance angle) silicon drift detection (SDD) energy dispersive x-ray (EDX) spectrometer. The new instrument will be modified at York to include added unique functionalities, along the lines of the research led by the group. Methods and some hardware will be transferred from the original proof-of-concept and aged (2005) first generation instrument at York. The advantages of the open aperture 'gas-in-microscope' concept promoted at York are expected to be especially significant at the lower accelerating voltages of 80 and 40 kV to be available to reduce damage due to specimen-electron beam interactions. The new instrument and attendant expertise will be organised, actively promoted, operated and managed as a new national capability with connections to the national SuperSTEM and ePSIC laboratories, including CI representation from both organisations, for advice and user guidance and active assistance external promotion and strategic as well as tactical management. Wide networking will add to the framework for organising the new capability but will not exclude more ad hoc bilateral interactions; in part to promote the core science needed at the heart of such an 'organisation'. The scientific benefits of the proposed centre for excellence in environmental aberration corrected STEM will greatly contribute to the current research initiatives in the UK related to nanomaterials for energy applications, information technologies/internet of things, and catalysis. The key contribution will be in fundamental understanding of the nanomaterials environment interactions enables trough atomistic imaging and analysis of the dynamic processes that take place either during material fabrication or in action. The project will make a significant contribution to what the future of the UK and of the world will look like; through better understanding of societal, scientific, economic, and environmental challenges and opportunities.

30 years' research on metal biorecovery from wastes has paid scant attention to strong CONTEMPORARY demands for (i) conservation of dwindling vital resources (e.g platinum group metals (PGM), recently rare earth elements, (REE), base metals (BMs) and uranium) and (ii) the unequivocal need to extract/refine them in a non-polluting, low-energy way. 21stC technologies increasingly rely on nanomaterials which have novel properties not seen in bulk materials. Bacteria can fabricate nanoparticles (NPs), bottom up, atom by atom, with exquisite fine control offered by enzymatic synthesis and bio-scaffolding that chemistry cannot emulate. Bio-nanoparticles have proven applications in green chemistry, low carbon energy, environmental protection and potentially in photonic applications. Bacteria can be grown cheaply at scale for facile production. We have shown that bacteria can make nanomaterials from secondary wastes, yielding, in some cases, a metallic mixture which can show better activity than 'pure' nanoparticles. Such fabrication of structured bimetallics can be hard to achieve chemically. For some metals like rare earths and uranium (which often co-occur in wastes) their biorecovery from scraps e.g. magnets (rare earths) and wastes (mixed U/rare earths), when separated, can make 'enriched' solids for delivery into further commercial refining to make new magnets (rare earths) or nuclear fuel (U). Biofabricating these solids is often beyond the ability of living cells but they can form scaffolds, with enzymatic processes harnessed to make biomineral precursors, often selectively. B3 will invoke tiered levels of complexity, maturity and risk. (i) Base metal mining wastes (e.g. Cu, Ni) will be biorefined into concentrated sludges for chemical reprocessing or alternatively to make base metal-bionanoproducts. (ii) Precious metal wastes will be converted into bionanomaterials for catalysis, environmental and energy applications. (iii) Rare earth metal wastes will be biomineralised for enriched feed into further refining or into new catalysts. (iv) Uranium-waste will be biorefined into mineral precursors for commercial nuclear fuels. In all, the environment will be spared dual impacts of both primary source pollution AND the high energy demand of processing from primary 'crude'. Metallic scraps are tougher, requiring acids for dissolution. Approaches will include the use of acidophilic bacteria, use of alkalinizing enzymes or using bacteria to first make a chemical catalyst (benignly) which can then convert the target metal of interest from the leachate into new nanomaterials (a hybrid living/nonliving system, already shown). Environmentally-friendly leaching & acids recycle will be evaluated and leaching processes optimised via extant predictive models. The interface between biology, chemistry, mineralogy and physics, exemplified by nanoparticles held in their unique 'biochemical nest', will receive special focus, being where major discoveries will be made; cutting edge technologies will relate structure to function, and validate the contribution of upstream waste doping or 'blending'; these, as well as novel materials processing, will increase bio-nanoparticle efficacy. Secondary wastes to be biorefined will include magnet scraps (rare earths), print cartridges (precious metals), road dusts (PMs, Fe,Ce) & metallurgical wastes (mixed rare earths/base metals/uranium). Their complex, often refractory nature gives a higher 'risk' than mine wastes but in compensation, the volumes are lower, & the scope for 'doping' or 'steering' to fabricate/steer engineered nanomaterials is correspondingly higher. B3 will have an embedded significant (~15%) Life Cycle Analysis iterative assessment of highlighted systems, with end-user trialling (supply chains; validations in conjunction with an industrial platform). B3 welcomes new 'joiners' from a raft of problem holders brought via Partner network backup.