Investigation of Graphene Oxide Nanosheets Dispersion in Water Using Molecular Dynamics Simulation Golsom Akhlamadia, Sayyed Jalil Mahdizadeha, Elaheh K. Goharshadi a, b,* a) Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad 91779, Iran b) Centre of Nano Research, Ferdowsi University of Mashhad, Mashhad 91779, Iran Background: Graphene oxide (GO) isone of the most interesting materials due to its excellent properties. GO has distinguishing features such as easy surface modifications, good biocompatibility, distinctive amphipathic nature, and superior mechanical properties[1]. GO is consisting of graphene sheet covalently bonded to oxygen groups. The amphipathic nature makes GO to be easily dispersed in lots of solvents [2]. An important challenge involves achieving its homogeneous colloidal suspensions. The forces between colloidal nanoparticles determine the dispersion and stability of the suspension. Various possible forces e.g. van der Waals, electrostatic, and solvation can exist between solid particles suspended in a liquid. Methods: Molecular-level simulations such as molecular dynamics (MD) can be useful in resolving the forces between colloidal suspensions. These simulations can take into account every single atom and molecule that is present in a colloidal suspension. It is possible to resolve the relative and absolute magnitudes of various colloidal forces using MD simulation. The purpose of this research is to investigate the factors influencing the dispersion of GO nanosheets in water using MD simulation. The stability of GO dispersions significantly depends on the degree of oxidation by attached oxygen groups and the number of layersas well as temperature. Results: The solubility parameter of water, δwater, was estimated to be 46.45 MPa1/2using MD simulation. The calculated values for δGO were 36.5, 38.2, 42,6, and 45.0 MPa1/2 for two, three, four, and five layers of GO, respectively. Conclusion:  The calculated of δwater (46.45 MPa1/2) is in a good agreement with its experimental value of 47.82MPa1/2 [2].  The simulation results show a strong dependence of δGO to the number of layers. The value of δGO increases as the number of layers increases and approaches to δwater. Keywords: Dispersion; Graphene Oxide; Molecular Dynamics; Colloidal forces References [1] Park S., An J., Jung I., Piner R. D., An S. J., Li X., Velamakanni A., Ruoff R. S., Nano

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