The aim of the project is characterization of the magnetic interactions in modified two- (2D) and three- (3D) dimensional graphene oxide (GO) structures. Graphene oxide similarly to graphene consist of hexagonal layered carbon rings with honeycomb structure. However, in contrary to graphene, graphene oxide is structure rich in structure defects and plethora of different oxygen functional groups which allow obtaining modified material for variety of potential applications. The structural modifications of GO influence its magnetic interactions. The durability of magnetic interactions is changing during weeks to months after the synthesis and long range magnetic interactions are vanishing after this time. It happens due to the surface diffusion of paramagnetic defects and edge states oxidation. In this work GO will be investigated after structural modification in two- and three-dimensional form with or without presence of transition metal ions which possess their own magnetic moments additionally modifying magnetic interactions. Along to research hypothesis, it is assumed the structural modifications will influence the magnetic interactions and allow obtaining magnetically stable structures.
Graphene aerogel obtained from ethyl alcohol (left), reduced graphene oxide aerogel obtained with Hummers method followed by Critical Point Drying (right)
The concept of the research involves the implementation of two tasks: i) synthesis of two- and three-dimensional structures based on the graphene oxide and ii) physicochemical analysis of the obtained structures with particular regard to magnetic characteristics. Graphene oxide will be prepared via modified Hummers method. Obtained 2D GO flakes will be modified via reduction (rGO), hydrogenation (hGO) and NH3 functionalization (aGO). On the basis of 2D few-layered GO flakes, 3D hydrogel structures will be formed via sol-gel process. One experiment involves gelation with assistance of typical reducing agents, the second chlorides of transition metal ion (Cu2+, Co2+, Ni4+, Cr3+, V3+). Moreover, xero- and aerogels will be prepared by oven drying and freeze-drying of hydrogels, respectively. Both of the obtained structures will be exposed to solution of transition metal chlorides in order to estimate ion adsorption properties and their influence on magnetic interactions. Physicochemical characterization of obtained structures will be performed after each step of preparation. The magnetic properties will be studied by Pulse (T1, T2, TM, ESEEM spectroscopy) and Continuous Wave (X/Q band) Electron Paramagnetic Resonance (EPR) techniques and magnetic susceptibility measurements (SQUID). Different spectroscopic (FT-IR, XPS, Raman spectroscopy) and microscopic (SEM-EDX, HR-TEM, AFM) methods available at NanoBioMedical Centre of Adam Mickiewicz University in Poznań will be used. Additionally, tribological measurements will be performed on xero- and aerogels. EPR measurements will be performed in Institute of Molecular Physics Polish Academy of Sciences in Poznań. The specific surface area (BET) and elemental analysis will be performed at Faculty of Chemistry of Adam Mickiewicz University.
Vitreous carbon aerogel obtained from sucrose
The proposed research related to magnetic interactions of the modified graphene oxide structures will broaden the knowledge of magnetism regarding the stability, electron spin relaxation in the synthesized systems fulfilling the assumptions of basic research. These systems may be used in the electronics industry in the construction of electrodes for batteries and supercapacitors. Aerogels - one of the lightest 3D carbon structures produced from the modified GO - can be used in environmental protection for water purification from heavy metals or absorption of petroleum products.
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