title: Taking a hard line with biotemplating: cobalt-doped magnetite magnetic nanoparticle arrays.
abstract: Rapid advancements made in technology, and the drive towards miniaturisation, means that we require reliable, sustainable and cost effective methods of manufacturing a wide range of nanomaterials. In this bioinspired study, we take advantage of millions of years of evolution, and adapt a biomineralisation protein for surface patterning of biotemplated magnetic nanoparticles (MNPs). We employ soft-lithographic micro-contact printing to pattern a recombinant version of the biomineralisation protein Mms6 (derived from the magnetotactic bacterium Magnetospirillum magneticum AMB-1). The Mms6 attaches to gold surfaces via a cysteine residue introduced into the N-terminal region. The surface bound protein biotemplates highly uniform MNPs of magnetite onto patterned surfaces during an aqueous mineralisation reaction (with a mean diameter of 90 ± 15 nm). The simple addition of 6% cobalt to the mineralisation reaction maintains the uniformity in grain size (with a mean diameter of 84 ± 14 nm), and results in the production of MNPs with a much higher coercivity (increased from ≈ 156 Oe to ≈ 377 Oe). Biotemplating magnetic nanoparticles on patterned surfaces could form a novel, environmentally friendly route for the production of bit-patterned media, potentially the next generation of ultra-high density magnetic data storage devices. This is a simple method to fine-tune the magnetic hardness of the surface biotemplated MNPs, and could easily be adapted to biotemplate a wide range of different nanomaterials on surfaces to create a range of biologically templated devices.
authors.affiliation: University of Sheffield, Department of Chemistry, Dainton Building, Sheffield, S3 7HF, UK. s.s.staniland@sheffield.ac.uk.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Bird
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Galloway
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Rawlings
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Bramble
authors.forename: Sarah S
authors.initials: SS
authors.lastname: Staniland
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D003035:Cobalt / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D042201:Magnetospirillum / Q000378:metabolism; D018625:Microscopy, Atomic Force; D010316:Particle Size; D058525:Quartz Crystal Microbalance Techniques; D013499:Surface Properties
chemical_list: D001426:Bacterial Proteins; D058185:Magnetite Nanoparticles; D003035:Cobalt; D006046:Gold