Dynamic Properties of Graphene Oxide Functionalized with l-Cysteine

Abstract

The surface functionalization of graphene oxide (GO) with L-cysteine is a potent candidate for applications like enzymatic and non-enzymatic bio-sensing and biomedical purposes. Though numerous studies are available detailing efficient synthesis to applications, their interaction with the solvent and the factors affecting the stability should have been considered. Characterizing Cys-GO through Raman, Fourier-transform infrared, and dynamic light scattering spectroscopy quantified the chemical nature and revealed varying particle size distribution compared to GO. This indicates that Cys-GO sheets possibly exist in different ensemble states in the aqueous solution. To probe into its dynamic behavior, classical all-atom simulations have been employed. The computational results align with the experimental differences observed for precursor graphene, GO, and functionalized Cys-GO. The results demonstrate that the presence of a disulfide bond between Cys-GO sheets stabilizes the structural dynamicity compared to the individual or dimer sheet. The interaction with water molecules introduces variable deformation through the interplay between diffusive and Brownian motion of solvent over the sheets. The disulfide bond holds the sheets together, enabling more inter-sheet interactions and reducing random movement. The study provides deep physical insights into graphene-based materials, paving the way for the design of nanosheets with tunable characteristics for future nanocomposite development and sensing applications.