Proteins, Polymers and Nanoparticles: Self-assembly Towards Functional Nanostructures

Abstract

Self-assembly is a fundamental phenomenon that drives every form of life. In the materials research world, the concept of self-assembly has been applied to synthesize or organize materials. Templates form an integral part of this endeavor, providing control and easier manipulation of the structures formed. The research in this thesis explores the theme of templated self-assembly to create hierarchical nanoparticle assemblies towards applications in future electronics. Firstly, a redox-active protein peroxiredoxin (Prx) was used as a template to synthesize and organize iron oxide nanoparticles. In this process, a ligandcontrolled approach was used to grow iron oxide nanoparticles in-situ, in Prx templates. Furthermore, the redox sensitivity of Prx was explored to organize in-situ grown nanoparticles into 1-D nanoparticle assemblies. The use of Prx templates holds promise to form nanowires and structures for electronic and magnetic applications. Many such applications would rely on the creation of organized surface arrays. Therefore, to organize the Prx assemblies in block copolymer scaffolds, PEGylation of Prx was explored as an option to solubilize Prx in organic solvents. At high PEG to protein molar ratios, PEGylation was found to disturb the supramolecular architecture of Prx, thus far prohibiting such co-assembly. Block copolymers were also explored as templates to develop bottom-up approaches for magnonic crystal fabrication. In one approach, block copolymer thin films were used as templates to fabricate nanoparticles on solid substrates. A combination of microscopy and scattering techniques were used to evaluate the organizational features of nanoparticles. Ferromagnetic resonance (FMR) spectroscopy was used to test the feasibility of the fabricated systems for spin wave generation and propagation. Finally, extending the block co-polymer micellar templating approach to presynthesized nanoparticles, block copolymer micelles were used as templates to direct the organization of polyoxometalate nanocrystals and cobalt ferrite nanoparticles into mesoscale assemblies. The structural and organizational features of POMs/nanoparticle organizations were evaluated by a combination of microscopy and scattering techniques. The mesoscale ordering of the micelles was found to be disrupted at a high loading of POMs, whilst nanoparticles seem to have disrupted the micellar ordering at comparatively low loadings. The mesoscale features of these POM/micelle systems hold promise for spintronic/magnonic applications. On the whole, the use of templates for magnonic applications opens up exciting avenues towards the fabrication of nextgeneration data storage or processing devices.