Carbon black as a cost-effective nanomodifier for (electro)chemical-free pre-treatment thermoplastic polyurethane-based 3D printed electrodes

Here, we report the investigation of carbon black as a cost-effective nanomodifier of thermoplastic polyurethane-based 3D printed electrodes for enhancing their electrochemical performances. The sensor was produced by scratching the working electrode with sandpaper, followed by the deposition of carbon black dispersion by drop casting. The morphological characterisation was carried out, showing the presence of a homogeneous coating of carbon black with a typical rough and spongy structure. Additionally, the electrochemical characterisation using electrochemical impedance spectroscopy highlighted the advantage of using carbon black as a nanomodifier of the working electrode surface after printing by obtaining the resistance of charge transfer equal to 327 ± 43 kΩ and 1.45 ± 0.06 kΩ for bare electrode and carbon black-modified electrode, respectively. When tested in cyclic voltammetry using ferro/ferricyanide, uric acid, dopamine, ascorbic acid, and free chlorine as target electroactive compounds, we demonstrated that the presence of carbon black cast onto the working electrode surface transformed the electrode from non-responsive to responsive electroanalytical tool. The analytical features of the developed responsive sensor were assessed for the detection of free chlorine in tap water with a linearity of 0.2–20 ppm and a limit of detection equal to 0.01 ppm. The accuracy was evaluated by spiking tap water samples with free chlorine concentrations equal to 0.5, 1, and 5 ppm, obtaining recovery percentages of (103 ± 2)%, (104 ± 3)%, and (95 ± 3)%, respectively. Additionally, the sustainability (electro)chemical-free pre-treatment thermoplastic polyurethane-based 3D printed electrodes modified with carbon black were evaluated by the White Analytical Chemistry principles. The advantages of 3D printed sensors modified with carbon black by drop casting were demonstrated, in terms of both the electrochemical performances and sustainable aspect, enlarging the use of carbon black as a nanomodifier to the 3D printed electrodes, beyond the 2D printed electrodes.