Enhanced electrochemical performance of 3D-printed electrodes via blue-laser irradiation and (electro)chemical treatment

Extrusion-based 3D printing technologies, especially fused filament fabrication (FFF) using conductive filaments, have significantly advanced in electroanalytical applications by enabling the fabrication of electrochemical sensors. Nonetheless, 3D-printed electrodes produced from commercially available conductive filaments (e.g., polylactic acid containing carbon black - CB/PLA) often contain a low amount of conductive material (similar to 20 % wt. carbon black), requiring surface activation protocols to enhance their electrochemical performance. In this study, we investigated the combination of blue-laser (BL) irradiation and (electro)chemical treatment (EC) to improve the performance of 3D-printed electrodes. For this purpose, 3D-printed CB/PLA electrodes were subject to blue laser activation (laser power = 280 mW and scan rate = 30 mm s(-1)) followed by an electrochemical procedure in 0.5 mol L-1 NaOH solution (application of +1.4 V and - 1.0 V both for 200 s). After the combined treatment, a considerable improvement in the voltammetric profile response (Ipa/Ipc = 1.00 and Delta Ep = 136 mV) was achieved using 1 mmol L-1 [Fe(CN)(6)](3-/4-) (equimolar concentration) as the redox probe when compared to polished electrodes (Ipa/Ipc = 0.85 and Delta Ep = 690 mV). Scanning electron microscopy, infrared spectroscopy data and X-ray photoelectron spectroscopy showed that the combined treatment promotes the remotion of insulating PLA material, exposing more conductive sites and functional groups. Moreover, electrochemical impedance spectroscopy results showed low resistance to charge transfer and capacitance double-layer measurements revealed an increase in the electroactive area after surface activation. As proof of concept, emerging contaminants such as hydroxychloroquine (HCQ) and paracetamol (PRT) were determined in tap water and pharmaceutical samples using treated 3D-printed CB/PLA electrodes and square-wave voltammetry. Linear ranges of 0.20 - 12.30 mu mol L-1 and 1.0-30.0 mu mol L-1 with limit of detection values of 0.01 and 0.2 mu mol L-1 were obtained for HCQ and PRT, respectively. Appropriate recovery values (90 - 111 %) for the analysis of spiked samples were achieved.