Optimizing Carbon\nStructures in Laser-Induced Graphene\nElectrodes Using Design of Experiments for Enhanced Electrochemical\nSensing Characteristics

In this study, we explored the morphological and electrochemical\nproperties of carbon-based electrodes derived from laser-induced graphene\n(LIG) and compared them to commercially available graphene-sheet screen-printed\nelectrodes (GS-SPEs). By optimizing the laser parameters (average\nlaser power, speed, and focus) using a design of experiments response\nsurface (DoE-RS) approach, binder-free LIG electrodes were achieved\nin a single-step process. Traditional trial-and-error methods can\nbe time-consuming and may not capture the interactions between all\nvariables effectively. To address this, we focused on linear resistance\nand substrate delamination to streamline the DoE-RS optimization process.\nTwo LIGs, designated LIG A and LIG B, were fabricated using distinct\nand optimized laser settings, which resulted in a sheet resistance\nof 25 ± 2 Ω/sq and 21 ± 1 Ω/sq, respectively.\nThese LIGs, characterized by scanning electron microscopy, Raman spectroscopy,\nand contact angle analysis, exhibited a highly porous morphology with\n13% pore coverage and a contact angle <50°, which significantly\nincreased their hydrophilicity when compared to the GS-SPE. For the\nelectrochemical studies, the oxidation of NO<sub>2</sub><sup>–</sup> ion by the graphene-based working electrodes was investigated, as\nit allowed for the direct comparison of the LIGs to the GS-SPE. These\nincluded cyclic voltammetry, electrochemical impedance spectroscopy,\nand differential pulsed voltammetry studies, which revealed that LIG\nelectrodes displayed a remarkable 500% increase in peak current during\nNO<sub>2</sub><sup>–</sup> oxidation compared to the GS-SPE.\nThe LIGs also demonstrated improved stability and sensitivity (420\n± 30 and 570 ± 10 nAμM<sup>–1</sup> cm<sup>–2</sup>) compared to the GS-SPE (73 ± 4 nAμM<sup>–1</sup> cm<sup>–2</sup>) in the oxidation of NO<sub>2</sub><sup>–</sup> ions; however, LIG B was more susceptible\nto ionic interference than LIG A. These findings highlight the value\nof applying statistical approaches such as DoE-RS to systematically\nimprove the LIG fabrication process, enabling the rapid production\nof optimized LIGs that outperform conventional carbon-based electrodes.