A rapid and sensitive electrochemical sensor for hydroxyl free radicals based on self-assembled monolayers of carboxyl functionalized graphene

In this work, carboxyl-functionalized graphene (CFG) was immobilized on glassy carbon electrode (GCE) by self-assembled monolayers (SAMs) based on covalent interaction with ethylenediamine as an arm linker. The obtained (CFG-NHCH 2 CH 2 NH)/GCE can be used as rapid and sensitive electrochemical sensor for hydroxyl free radicals (•OH). In the process of determination, the concentration of •OH was acquired not directly but through the only captured product 3,4-dihydroxybenzoic acid (3,4-DHBA), which is adopting 4-hydroxybenzoic acid (4-HBA) as the •OH trap. The glassy carbon electrode modified with carboxyl-functionalized graphene exhibits well conductivity and electron transfer ability, and also displays good electrocatalytic activity towards the electrochemical redox of 3,4-DHBA. The proposed sensor displays a good linear range from 1.0 to 450.0 μM for 3,4-DHBA with a low detection limit of 0.17 μM (S/ N  = 3). More importantly, the sensing platform can be successfully applied for •OH detection with the 4-HBA as the •OH trap.