Adsorption-Enhanced Sensitivity for Electrochemical Sensing of Diclofenac by Poly(ether sulfone)-Based Laser-Induced Graphene

Emerging contaminants are a matter of growing concern for environmental and human health and safety, requiring efficient and affordable sensing platforms. Laser-induced graphene (LIG) is a novel material with a 3D porous graphene structure that can be fabricated in a simple one-step fabrication process. However, most LIG-based works in electrochemical sensors are limited to polyimide (PI)-based platforms, thus limiting the purview of properties of LIG dependent on the substrate-laser interaction. Diclofenac (DCF), a nonsteroidal anti-inflammatory drug, is an emerging contaminant in water and wastewater that threatens aquatic and terrestrial life. Furthermore, LIG-based sensors have not been used to sense DCF. In this work, we demonstrate the spontaneous adsorption behavior of LIG toward DCF without applying any external potential. This spontaneous adsorption phenomenon can enhance the sensitivity per the characteristics of the tested water samples and permissible standards to be followed. Poly(ether sulfone)-based LIG (PES-LIG) is found to be more responsive to laser irradiation than PI-LIG due to its highly porous surface and fibrous nature, imparting more electrochemical sites and adsorption area for DCF. These characteristics lead to a higher sensitivity of 0.2774 μA μM^-1 toward DCF sensing for PES-LIG with a limit of detection of 0.1 μM. The sensors were applied for DCF measurement in wastewater and tap water samples with appreciable selectivity. The specific adsorption behavior of LIG toward DCF could pave the way for new pathways in emerging contaminant sensing and removal as well as for other applications.