Development and characterization of gold nanoparticle-based impedimetric sensors for PFAS detection

Per and Poly fluoroalkyl substances (PFAS) consist in a class of human-made chemicals used in various industrial and consumer products. However, due to their toxicity, strong chemical stability, and their persistence even in extreme conditions, these substances represent a risk to human health and to the environment. Recently, the Veneto region in Italy has encountered severe PFAS contaminations affecting groundwater, drinking water supplies, and agriculture areas, thus in this context the demand for rapid and accessible monitoring solution has increased. My thesis is a preliminary study focused on the development and characterization of an impedimetric sensor for PFAS surrogates’ detection. This work was in collaboration with the Department of Chemical Sciences (DiSC) of the University of Padua, where I synthesized - with Laser Ablations - and deposited – using spray-coating on glass substrates - the gold nanoparticles to fabricate the electrodes used in the electrochemical system. To monitor the surface characteristics of the AuNP electrodes, I employed Electrochemical Impedance Spectroscopy measurements. After testing reproducibility and stability of the fabricated AuNP electrodes, I performed functionalization procedures with self-assembled-monolayers (SAMs) of 11-mercaptoundecanoic acid (11-MUA, which was activated with EDC/NHS to enable a detectable binding with the octylamine, a non-toxic molecule used as PFAS surrogate. EIS measurements results showed an expected increase in the charge transfer resistance (Rct) after functionalization with MUA. In this phase of my work, I carried out various functionalization protocols to find the most effective and suitable procedure on both AuNP electrodes and screen-printed commercial electrodes. In the last part of my thesis work, I performed additional experiments using 3-mercaptopropionic acid (3-MPA) instead of 11-MUA to evaluate the impact of SAM thickness over the capability of octylamine detection. The experimental results demonstrate the potentiality of using AuNP-based electrodes for the indirect PFAS detection. However, future developments are needed to optimize these electrochemical devices for environmental monitoring applications.