Solvent-Assisted Modification of Laser-Induced Graphene for Surface-Enhanced Electrochemical Response

The fabrication and application of laser-induced graphene (LIG) have received significant interest across various research fields, particularly in sensing technologies. Herein, we investigated the surface modification of LIG electrodes with different solvents and demonstrated that dimethyl sulfoxide (DMSO) enhances their electrochemical activity. Importantly, our findings reveal that solvent treatments themselves can induce significant modifications on the electrode surface (e.g., changes in functional groups, wettability, and morphology), which must be carefully considered in sensor design and optimization. The application of a microliter aliquot of DMSO to the LIG surface significantly altered its wettability, promoting a transition to hydrophilic behavior, which was verified by contact-angle measurements. AFM and XRD results indicate that DMSO treatment promotes the rearrangement of disordered carbon atoms, minimizing localized structural defects and enabling more efficient π-π stacking between graphene sheets. The cyclic voltammetric response of the [Fe(CN)₆]^3-/4- redox probe showed a 3-fold increase in peak current. The enhanced electrochemical effect of DMSO surface changes on LIG electrodes was also confirmed in the presence of several organic species, and a substantial current increase was verified by the effect of DMSO. As proof-of-concept, the antibiotic sulfanilamide was detected in synthetic urine and water samples using differential-pulse voltammetry on DMSO-treated LIG. Under optimized conditions, the sensor exhibited a linear response in the range of 0.3-9.0 μmol L^-1 with a limit of detection of 0.09 μmol L^-1 and satisfactory recovery values (90-104%).