Femtosecond Laser One-Step Direct Writing Electrodes with Ag NPs-Graphite Carbon Composites for Electrochemical Sensing

The next generation of green electronic products will be flexible, eco-friendly, have arbitrary patterning, and be produced using simple methods. Here, a silver nanoparticles (Ag NPs)–graphite carbon composite-based electrochemical sensor is patterned on a flexible substrate by one-step in situ femtosecond (fs) laser fabrication. Alkali lignin is used as a precursor and nontoxic natural reducing agent to reduce aqueous silver nitrate to produce Ag NPs. The fs laser carbonization process converts lignin into graphite carbon electrodes with diverse three-dimensional (3D) micro/nano morphologies, causing less thermal damage to the Ag NPs and thin substrate. The 3D micro/nano morphologies combined with Ag NPs effectively increase the active surface area, conductivity, and catalytic activity of the electrode, which is further applied as an electrochemical sensor. This sensor has a wide linear detection range of nitrite from 1–4000 × 10⁻⁶ m, a detection limit of 0.117 × 10⁻⁶ m (S/N = 3), and long lifetime of 30 days. The sensor also has the potential to detect dopamine (DA). A detection limit of 0.098 × 10⁻⁶ m (S/N = 3) is obtained, with a linear detection range of 1–45 × 10⁻⁶ m. The sensor demonstrates a wide range of applications in food safety and human health-related detection.