The utilization of biological factors in the design, synthesis and fabrication of nano-scaled materials and devices presents novel, large scale solutions for the realization of future technologies. In particular, we have genetically modified the M13 Filamentous Bacteriophage for its use as a biological scaffold in the peptide-controlled nucleation and patterning of nanoscale semiconducting and magnetic materials. Through evolutionary phage display screening of inorganic substrates, ftunctional peptides that influence material properties such as size, phase and composition during nucleation have been identified. The incorporation of these specific, nucleating peptides into the generic scaffold of the M13 coat structure provides a viable linear template for the directed synthesis of semiconducting and magnetic nanowires. Through further modification of the remaining proteins on the virus scaffold, other functionalities can be incorporated such as the directed patterning of the virus/nanowires assemblies into nanoscaled devices with tunable properties as determined by the genetic information carried within the virus scaffold. Multi-functional viruses provide a truly self assembled system for the design and execution of a myriad of nanoscaled devices in a green, scalable and cost effective manner. Thesis Supervisor: Angela M. Belcher Title: John Chipman Professor of Materials Science & Engineering and Biological Engineering.

Biological scaffolds for the peptide-directed assembly of nanoscale materials and devices

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Abiotic- and Biotic-Formation of Manganese Oxides and Their Fate in Environmental Systems

Selective oxidation reactions are important transformations for the production of fine chemicals. However, there is a need to replace current oxidation methods by more sustainable alternatives. In this respect the use of biocatalysts offers a large benefit, because they operate under mild conditions, and their use is accompanied by high chemo-, regio- and stereoselectivities in reactions of multifunctional molecules. In nature, oxidation reactions are catalyzed by so-called redox enzymes which form the class of oxidoreductases (EC 1). Despite the potential value of oxidoreductases for industrial oxidation reactions, they do not find wide application in fine chemicals industry. The reasons thereof are diverse but the crucial problems are commercial availability, operational stability, scope and, in some cases, lack of an effective method for co-factor regeneration where necessary. In order to facilitate the large scale application of enzymes as catalysts, these drawbacks need to be overcome. One approach is to design new (semi)synthetic biocatalysts with improved stability and comparable or better selectivity and activity to natural enzymes. The focus of this thesis is on the design of oxidative enzymes that can be readily applied in fine chemical synthesis. A number of approaches were investigated that combine the advantages of biocatalysis, with the activity and versatility of chemo-catalysts. This brought us to the approach of designing protein-metal hybrids that can act as either oxidases or peroxidases.

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Protein-Metal Hybrids as Catalysts for Selective Oxidations

This paper reports on the progress in developing self organized nanoparticulate arrays for magnetic recording at densities beyond 30 Gbit/cm2 (200 Gbit/in2), and in particular describes the beneficial use of biological templates in developing such arrays. Chemically synthesized, high magnetocrystalline anisotropy magnetic nanoparticles have demonstrated extremely narrow size distributions that are critical in reducing media noise. Due to their monodispersity, they also exhibit emergent self-patterning that could potentially support bit-per-particle densities up to 2–8 Tbit/cm2 (10–50 Tbit/in2). High anisotropy L10 CoPt precursor grains are prepared within apoferritin from aqueous reactants, with synthesis conditions controlling grain size, structure and composition. Smooth films on glass disk substrates are produced by either spin- or dip-coating from aqueous dispersions of the precursor material. Films are typically annealed at 590 °C for 60 minutes with a 19 kPa (190 mBar) partial pressure of H2 to form the L10 phase. We report on recently produced films that have demonstrated moderate-density recording using a contact drag tester with commercial, 0.35 µm-wide magnetoresistive (MR) heads. The highest areal density currently achieved for these nanoparticulate films is 0.93 Gbit/cm2 (6.0 Gbit/in2).

Magnetic recording at high densities on protein-derived CoPt nanoparticles

We have developed virus-based protein cage functional materials for catalysis and optical coatings. The unique properties of the viral particles, such as in vitro reversible self-assembly with functional nanoparticles or molecules incorporated, their capability of chemical or genetic modification and the ability to self-assembly into high-order structures, were employed to introduce new or different functions into these catalytic and/or optical materials. These studies help to gain further insight in the development of virus-based materials.

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Viral Protein Cages as Building Blocks for Functional Materials

A novel system has been used to manufacture nanoparticulate Cu:Pt with an average diameter of 8nm and very small standard deviation. The system uses a protein called ferritin that normally stores iron in viva, but this iron can be chemically removed. The hollow protein can then be used to grow Co:Pt nanopmicles which are subsequently heat treated to promote a particular crystalline phase. The femtin can be deposited onto a substrate where it naturally self assembles into an HCP monolayer under appropriate conditions. If the protein is then carbonised or otherwise removed, a regular HCP close packed array of 8nm Co:Pt particles is left. The theoretical storage densit of a thin film exploiting the patterned qualities of the HCP arrangement is 4.5 Tbitshu , Work is presented regarding the development of a magnetic thin film media based on these processes.

J. Wiggins

Papers

Self assembled nanoparticulate copt for data storage applications