Electrochemiluminescence in Thermo-Responsive Hydrogel Films with Tunable Thickness

Electrochemiluminescence (ECL) has attracted considerable interest for many applications such as microscopy, (bio)analysis, light-emitting materials or devices. In this work, we report the fabrication and characterization of ECL-active hydrogel films with tunable thickness. The redox films were prepared by electrochemically-assisted radical polymerization by potential cycling of a PBS solution containing the monomer N-isopropylacrylamide, the initiator potassium persulfate, the cross-linker N,N '-methylenebis(acrylamide) and the Ru(bpy)(3) monomer. The deposits were easily prepared in a rapid and well-controlled one-step procedure. The resulting homogeneous films are composed of a poly(N-isopropylacrylamide) (pNIPAM) matrix, which incorporates covalently [Ru(bpy)(3)](2+) centers. The thickness and the number of ECL-active sites is tuned by controlling the number of voltammetric scans. The deposited pNIPAM films are permeable to water-soluble chemicals such as the coreactant tri-n-propylamine (TPrA). The voltammetric characterization shows a continuous increase of the number of redox-active sites. Results indicate that ECL signals are proportional to the number of electrodeposited [Ru(bpy)(3)](2+) centers. Such approach combining ECL and stimuli-responsive hydrogels open exciting prospects for developing new (bio)sensing materials.