Developing Biotemplated Data Storage: Room Temperature Biomineralization of L1₀ CoPt Magnetic Nanoparticles

Abstract

L10 cobalt platinum can be used to record data at approximately sixfold higher densities than it is possible to on existing hard disks. Currently, fabricating L10 CoPt requires high temperatures (≈500 °C) and expensive equipment. One ecological alternative is to exploit biomolecules that template nanomaterials at ambient temperatures. Here, it is demonstrated that a dual affinity peptide (DAP) can be used to biotemplate L10 CoPt onto a surface at room temperature from an aqueous solution. One part of the peptide nucleates and controls the growth of CoPt nanoparticles from solution, and the other part binds to SiO2. A native silicon oxide surface is functionalized with a high loading of the DAP using microcontact printing. The DAP biotemplates a monolayer of uniformly sized and shaped nanoparticles when immobilized on the silicon surface. X‐ray diffraction shows that the biotemplated nanoparticles have the L10 CoPt crystal structure, and magnetic measurements reveal stable, multiparticle zones of interaction, similar to those seen in perpendicular recording media. This is the first time that the L10 phase of CoPt has been formed without high temperature/vacuum treatment (e.g., annealing or sputtering) and offers a significant advancement toward developing environmentally friendly, biotemplated materials for use in data storage.

Nano- and micro-patterning biotemplated magnetic CoPt arrays

“…Due to the overlap of the Au Lα and Pt Lα peaks, it was impossible to quantify the ratio of Co : Pt, as the abundance of Pt is overestimated by the fitting (≈5 : 7 Co : Pt). In our previous work 43 using this biotemplating CoPt sequence on a silicon surface, EDX showed a 1 : 1 ratio of Co : Pt in the surface biotemplated MNPs using these reaction conditions. Therefore it is likely that stoichiometric CoPt rather than CoPt 3 is biotemplated by the cys_CoPt peptide on the surface.…”

“…We previously reported that a molar excess of Co 2+ to Pt 2+ (3 : 1) in the mineralisation solution is necessary to achieve the desired 1 : 1 ratio of Co : Pt in the biotemplated metallic MNPs. 43,48 Here we find that control of the metallisation temp- erature is essential to ensuring that MNPs are formed by the cys_CoPt peptide. Mineralising at 18 °C allowed the biotemplating peptide to consistently form uniform MNPs on the substrates.…”

“…This higher surface density of peptide could enhance the templating of smaller, more uniform MNPs (12 ± 4 nm) when compared to DAP-templated particles (17 ± 9 nm). 43 The surface biotemplated particles are also the most equidimensional of all the samples analysed (aspect ratio (AR) 0.87 ± 0.09, see Table 1). Control particles were formed from a bulk solution with no biotemplate (bulk), and in the presence of 10 μg mL −1 of the cys-tagged peptide (cys_CoPt peptide, CGSGKTHEIHSPLLHK) and a non-cys-tagged version (CoPt peptide, GSGKTHEIHSPLLHK).…”

A novel design strategy for nanoparticles on nanopatterns: interferometric lithographic patterning of Mms6 biotemplated magnetic nanoparticles

“… 49 Some of these biopanning procedures are able to biotemplate the formation of MNPs of Pt alloys of Co and Fe, and organise these materials onto surfaces. 11 , 12 , 50 These materials, when in the L1 0 phase, are considered ideal for BPM, as their high magnetocrystalline energy means they maintain their magnetic domain at dimensions of a few nanometres. 51 – 53 …”

Using a biomimetic membrane surface experiment to investigate the activity of the magnetite biomineralisation protein Mms6

“…The longest and shortest axis of ≈100 MNPs per sample was recorded from representative SEM or TEM images in ImageJ software, 29 and these data were fitted in GraphPad Prism. The density of the MNPs on the surface was adapted from the method described in Galloway et al 30 The number of particles on a randomly selected 1 μm 2 area (of the biomolecule decorated surface) from five representative images was averaged for each sample. The approximate area occupied by the particles was estimated using the mean size of the MNPs calculated by grainsize analysis.…”