Fabrication, Functionalization and electrochemical characterization of rGO-based electrodes

This thesis focuses on the development and electrochemical characterization of an advanced nanostructured platform based on reduced graphene oxide (rGO) decorated with gold nanoparticles (AuNPs), fabricated using a rapid and low-cost laser-scribing technique. The integration of the electronic properties of graphene with the chemical versatility of gold nanoparticles addresses the growing need for point-of-care diagnostic sensors that are sensitive, cost-effective, and easily manufactured at scale. The first step of the research involved the fabrication and electrochemical activation of the electrodes in an acidic environment, a fundamental procedure for stabilizing the surface and quantifying the electroactive area available for anchoring future bioreceptors. Subsequently, surface functionalization was explored using two graphene derivatives: nitrogen-doped carboxylated graphene (NGA) and 1,3-diamino-2-propanol-modified graphene (GCystDAP). These materials were chosen to enhance the transducer's chemical binding capacity and improve signal response. Using electrochemical techniques such as cyclic voltammetry (CV) and square-wave voltammetry (SWV), a detailed analysis of the electron transfer kinetics and the system's sensitivity to redox probes such as methylene blue was conducted. The results highlighted a critical balance between the deposited nanomaterial loading and the sensor's performance: intermediate loadings ensured excellent surface accessibility, while excessive concentrations induced passivation and morphological instability. In conclusion, the study validates the effectiveness of the rGO@AuNPs platform as a robust basis for the development of high-performance electrochemical biosensors for the detection of DNA, aptamers, or antibodies.