Tuning electrochemical properties of 3D-printed PLA/carbon black electrodes via diamondized nanocarbon functionalization

This work investigates the influence of diamondized nanocarbon (DNC) surface charge on the performance of 3D-printed CB/PLA electrodes for paracetamol detection. Three filaments were prepared by the thermal method, incorporating DNCs with different zeta potentials, one positive (+20 mV) and two negative (-30 mV and -45 mV). Surface characterization by XPS and Raman spectroscopy revealed that DNC charge affects dispersion, polymer coverage, and the exposure of carbon black domains, whereas SEM images showed that positively charged DNCs tend to aggregate, whereas negatively charged DNCs remain well-dispersed. Contact angle measurements indicated increased hydrophilicity for electrodes containing negatively charged DNCs. Electrochemical analysis demonstrated lower charge-transfer resistance and superior current response for these electrodes, with an extended linear range and improved detection limits for paracetamol (∼1.5 times higher than positively charged DNCs). Overall, the results highlight that the DNC zeta potential is a key parameter for optimizing 3D-printed electrodes, providing a simple, low-cost strategy for the fabrication of portable and high-performance electrochemical sensors. Importantly, this is the first report demonstrating that DNC zeta potential significantly influences filament synthesis for electrochemical applications, opening new opportunities for the incorporation of various nanoparticles into filament composite.