Laser Masking Using Multilayer Paperboard to Fabricate Well-Defined Laser-Induced Graphene Electrodes for Electrochemical Sensing of Heroin

Abstract

Dimensionally controlled fabrication of laser-induced graphene (LIG) electrodes on cellulose-rich waste substrates remains challenging because lateral heat spreading during CO2 laser processing can broaden electrode features and reduce device-to-device reproducibility. Here, we report a waste-derived nanocarbon electrode platform in which postconsumer multilayer Tetra Pak cartons act simultaneously as the cellulose precursor and the processing architecture for intrinsic laser masking. The built-in polyethylene-aluminum laminate confines laser-induced graphitization to mechanically exposed paperboard regions, suppresses lateral carbonization, and yields TP-LIG features with a dimensional deviation of only ∼1.3%, compared with ∼17% for paper-LIG. After borax pretreatment and laser scribing (8.3 W, 80 mm s–1), TP-LIG was transferred by a water-assisted peel-off process onto adhesive tapes or disposable gloves, producing thin, flexible, ink-free three-electrode platforms. SEM/EDS and Raman analyses confirmed a porous, boron-containing graphene-like network, while electrochemical testing identified the face-down transferred electrode as the preferred interface because of its low charge-transfer resistance (Rct = 46 ± 7 Ω) and fast heterogeneous electron-transfer rate (keff0 = 3.65 × 10–3 cm s–1). As an application-oriented demonstration, the transTP-LIG electrode was used for square-wave voltammetric heroin sensing, providing two characteristic oxidation peaks and a quantitative peak II response over 2.0–800 μmol L–1 with a detection limit of 0.91 μmol L–1. Diluted artificial-urine spike-recovery experiments gave recoveries of 98.31–103.19% using peak II. This work introduces intrinsic laser masking as a simple route to high-fidelity, transferable LIG electrodes from multilayer packaging waste and demonstrates their utility for proof-of-concept electrochemical sensing of a forensic analyte in a simulated matrix.