Graphene oxide quantum dots (GOQD) covalently immobilized in hydrogels have shown great promise as artificial enzymes for the photodegradation of the organic dye rhodamine B (RhB). Suitably functionalized with cross-linkable 3-(triethoxysilyl)propyl methacrylate (MPS) units, GOQD-MPS were incorporated by free radical copolymerization into poly[2-(Methacryloyloxy)ethyl]trimethylammonium]-co-(3-Sulfopropylmethacrylate) 50:50 (A50coS50) hydrogels with known antiadhesive properties. The peroxidase mimetic activity of GOQD solutions for the oxidation of chromogenic peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in presence of hydrogen peroxide increased significantly upon functionalization with MPS. Consequently, composite GOQD-A50coS50 hydrogels also exhibited high peroxidase activity for TMB oxidation. Moreover, GOQD-MPS solutions and GOQD-A50coS50 hydrogels showed remarkable catalytic activity for degradation of model RhB dye in darkness, an activity that was notably enhanced by visible light irradiation. The photoactivity depended on GOQD-MPS loading and hydrogel volume. Interestingly, GOQD-A50coS50 hydrogels retained the high photocatalytic activity after several months stored wet as well as after undergoing drying-rehydration processes, key from a practical point of view for applications in water treatment. The activity of rehydrated hydrogels for RhB photodegradation was only reduced by 15% compared to the activity of a non-dried hydrogel under the same test conditions.
