(201aj) Sustainable Design of Carbon Nanomaterials: Decoupling the Role of Material Structure and Surface Chemistry on Electrochemical and Biological Activities

The unique structural and tunable physiochemical properties of carbon nanomaterials (CNMs) have enabled recent advancements in their design, leading to a wide range of innovative applications in various technologies, from electronic to biomedical devices. It is increasingly understood that rational design is critical to advance potential applications and proactively preclude adverse consequences of CNMs. Central to this approach is the establishment of parametric relationships that correlate material properties to both their functional performance and inherent hazard. Herein, the overarching goal is to decouple the causative mechanisms of material structure and surface chemistry as it relates to the electrochemical (a desired function) and biological activities of graphene oxide (GO). The results are evaluated in the context of established relationships between surface chemistry and oxygen functionalized multi-walled carbon nanotubes (O-MWCNTs). GO and O-MWCNTs, two predominant CNM analogs, share similar chemical composition while possessing discrete structural and electronic properties, which enables the investigation of structure- and surface-driven impacts on electrochemical and biological behaviors. After systematic surface modification to GO using thermal annealing and chemical reduction methods, our approach leverages comprehensive characterization (using AFM, TGA, XPS, ATR-FTIR, Raman, and DLS) to identify their physicochemical characteristics that govern their electrochemical and biological activities. The electrocatalytic properties of GO/rGO samples towards ORR provides a metric for the electrochemical activity and the propensity for samples to oxidize cellular biomolecules serves as the biological activity metric. The results indicate that surface chemistry is a viable design handle to control both electrochemical and biological activities. Rather than a single direct property (i.e., relative presence of carbonyl-containing moieties as was determined for MWCNTs), it is a balance of multiple consequential properties (extent of dispersion, defect density, and electrical conductivity) in combination with the relative presence of carbonyl moieties that synergistically contribute to electrochemical and biological activities. The identification of these governing physicochemical properties aims to inform the establishment of design parameters to guide the rational and safe design of CNMs, and thereby contribute to advancement of sustainable nanotechnology.