(361b) Novel 2-D Graphene- 0-D Magnetic Nanoparticle Interfacial Composites

Graphene, a monolayer of carbon, has exceptional electron mobility and flexibility. These properties have been explored for electronic, energy, and biosensing applications. However, graphene lacks magnetic ordering in its native form, which has strongly limited its ability to be employed in magneto-electronic and spintronic applications. Additionally, many of the existing magnetic induction strategies for graphene were found to disrupt its inherent electronic properties. A recent study showed that long range magnetization could be induced in graphene while preserving its intrinsic properties by placing graphene on top of a magnetic material.[1] Inspired by this approach, this research examines the potential of superparamagnetic iron oxide nanoparticles (SPIONs) as a means to induce magnetic properties in graphene. In contrast to previous thin film methods, this approach could permit local control over the magnetic ordering by self-assembly of magnetic nanoparticles on graphene in specific orientations. These 0-D nanoparticle- 2-D graphene composites could thus enable emergent magnetic behaviors.

In the present study, composites were synthesized by deposition of SPIONs on a silicon dioxide substrate onto which a graphene monolayer is transferred. This approach permits subsequent electron transport measurements of the composite. Controlled and scalable assembly of SPIONs was evaluated using self-assembly techniques, such as spin coating[2] and Langmuir Blodgett deposition. In addition, encapsulation of SPIONs in micelles and subsequent ordering was evaluated as a method to yield ordered arrays of particles with defined spacing[3]. As a first approach, the effects of parameters such as wetting of the substrate, dispersion of nanoparticles, and solvent vapor pressure were studied and optimized for SPION deposition. Composite surface topography was characterized using Atomic Force Microscopy (AFM). Then, a monolayer of graphene was transferred to each substrate to achieve the final composite. AFM and Magnetic Force Microscopy (MFM) were used to characterize the surface and magnetic topography of the final composite. Raman spectroscopy was used to detect perturbations in graphene properties resulting from the transfer process. Initial experiments were conducted using random deposition of nanoparticles and yielded successful composite fabrication. Magnetic and electronic properties of the final composite were evaluated for potential to exhibit the Hall effect. This research may enable magnetic functionality in graphene, increasing its applicability in magnetic storage. In addition, these findings could facilitate assembly of other novel 0D-2D composites.

[1] Z. Wang, C. Tang, R. Sachs, Y. Barlas, J. Shi, Proximity-induced ferromagnetism in graphene revealed by the anomalous Hall effect, Phys Rev Lett, 114 (2015) 016603.

[2] J.-Y. Liou, Y.-S. Sun, Monolayers of Diblock Copolymer Micelles by Spin-Coating fromo-Xylene on SiOx/Si Studied in Real and Reciprocal Space, Macromolecules, 45 (2012) 1963-1971.

[3] J.P. Spatz, S. Mössmer, C. Hartmann, M. Möller, T. Herzog, M. Krieger, H.-G. Boyen, P. Ziemann, B. Kabius, Ordered Deposition of Inorganic Clusters from Micellar Block Copolymer Films, Langmuir, 16 (2000) 407-415.