Resubmission novel bionanocatalysts and nanomagnets from solutions and metal bearing wastes

The property of matter changes at the nanoscale, because atoms at the surface of a crystal have different properties from those buried within it. Nanocrystals have a large proportion of surface atoms so these revealed properties could be utilised, including enhanced catalytic/magnetic properties. However they are unstable during manufacture and are difficult to make because they want to agglomerate. When this happens their properties are lost. Agglomeration can be prevented by using molecular 'cradles'. This is difficult and expensive: the cradle must shield each nanoparticle from its neighbours, but allow some area to remain exposed. Bacterial surfaces provide good cradles. Metallic nanoparticles are made by bacterial enzyme action, and cradling by local biomolecules as they grow, individually, on bacterial surfaces. Examples are precious metals (PMs: Pd,Pt,Au) and iron (oxides). PMs are reduced by bacteria to the metallic state. Fe oxides exist in various mineral forms which are made and chosen via combinations of bacterial action, and chemical reactions in the bacterially-influenced 'reaction space'. The net results are supported catalysts & magnets with special properties attributable to their nanosize. Traditionally PMs make good chemical catalysts, and Fe-oxides make good magnets, but at the nanoscale these distinctions blur: palladium is ferromagnetic while Fe oxides have catalytic activity. Even better, hybrid PM/Fe nanoparticles are BETTER in both applications than single metals but nobody has attempted to bio-direct the synthesis of hybrid nanoparticles (called bimetallic or trimetallic clusters). The instability of nanoparticles makes this very difficult indeed using chemistry. Bacteria can make mixed metal nanoparticles from mixed solutions and they can even do this by scavenging the metals from liquid wastes. Indeed, some bacteria-bound trimetallics were found to have better catalytic properties than mono- nanocrystals. This may be due to the intruding metal forcing changes in the crystal structure so that 'buried' atoms are persuaded to think that they are more like surface ones. Similar changes could also be brought about by application of electromagnetic fields (EMF; dielectric processing) during and following crystal synthesis but this has not been tried before. A combination of stable nanoparticles on bacteria plus dielectric processing could make a new generation of supernanoparticles, far in advance of what we already have. We aim to define the potential for making completely new materials using a portfolio of our bacteria as the catalysts for nanoparticle synthesis, and support. Some bacteria reduce PMs, some make ferric oxides, some do both. We will biomanufacture nanoscale chemical catalysts (PMs), nanomagnets (Fe), swop to get PM-magnets and Fe-catalysts and then combine them to make novel PM/Fe hybrids. We will relate what we make to how we make it, i.e the bacterial activity/surface properties and the crystals made. The industrial Partner will dielectric-process the bionanoparticles to further enhance their properties and a collaboration with Cardiff will use electron microscopy to be able to see what we have made, down to the atomic level. We will do example catalytic and magnetic testing of the bionanomaterials in the Universities against commercial standard materials. Mainly we will use pure metal solutions and bacterial strains for fundamental study. Finally, with the best bacteria, we will briefly look at example novel bionanomaterials made from mining wastes (Fe) and industrial wastes (Pd/Au) since we know these can work even better. We will use multifunctional bacteria and also some enhanced by mutations as appropriate

We will test the hypothesis that bionanomanufacturing makes novel nanomaterials that chemistry cannot; nanoparticles have unique properties but chemically supporting them to prevent agglomeration, & bulk synthesis are difficult/expensive. Bacterial surfaces are used to pattern, template & support stable metal nanocluster deposition & nanoparticle growth, promoted & controlled enzymatically.1. We will explore feasibility to make bionanocatalysts/ nanomagnets in 3 examples: (i) precious metal (PM) & Fe-based bionanocatalysts; (ii) PM/Fe based bionanomagnets; (iii) bacteria which deposit both PMs + Fe, directed to hybrid & bimetallic cluster biosynthesis, a major challenge conventionally. 2. We will establish biogrowth & processing methods for optical particle size/dispersion for potential applications. 3. We will apply dielectric processing to extant bionanocrystals & during the biogrowth process, determining optimal conditions for stability & activity. 4. We will look at crystal structures (using solid state & synchrotron-methods: EXAFS, XANES). magnetic (SQUID, XMCD) and surface phenomena (high resolution atomic level TEM/AFM to map crystal surface defects, kinks & terraces where reactions happen), relating structure to function, to help establish WHY BIOnanocrystals can have better activity than their chemical counterparts. Contrary to common perception nano-Fe(III) is catalytic and nano-Pd(0) is ferromagnetic. We will explore these potential multifunctionalities, uniting magnetic & catalytic phenomena within electron spin concepts, regarding the bionanocrystals as inorganic overlayers ('molecular amplifiers') of enzymatic systems, developing a strategy for future applications-targeted nanomaterials fabrication: a 'virtual shop' of niche products based on a microbial portfolio developed and tested within the study. Last, we will briefly examine biorecovery of active PMs/Fe from wastes, addressing dual 'global' problems of waste disposal & resource efficiency.