Ready-to-use optical H2O2 sensor based on stimuli-responsive polyacrylic film and nanofibers containing spiropyran

Abstract

Nowadays, design of conventional and efficient optical H2O2 sensors would be of great importance due to their lower cost and ease of follow-up, compared to the other widely used techniques such as electrochemical or chromatographic methods. Here, stimuli-responsive sensors containing photochromic (R/S)-2-(3′,3′-dimethyl-6-nitro-3′H-spiro[chromene-2,2′-indole]-1′-yl) ethanol (SPOH) and acrylic terpolymer film or nanofibers were prepared for H2O2 detection through a reaction-induced and concentration-dependent process. The polymer phase acts as an efficient substrate for exploitation of such sensors in aqueous media. Poly(methyl methacrylate-butyl acrylate-hydroxyethyl methacrylate) (MBH) was prepared via miniemulsion polymerization and its chemical structure was characterized by FTIR and 1H NMR spectroscopies. Then, it was doped with SPOH and the corresponding film (MBH/SPOH@F) and nanofibers (MBH/SPOH@NF) were fabricated via spin-coating and electrospinning techniques, respectively, and their morphologies were investigated by SEM. Colorimetric analyses were employed to evaluate performance of the obtained samples toward H2O2 after sensitization by UV irradiation. Both samples demonstrated visual color changes together with decrement in maximum absorption wavelengths with the increase in H2O2 concentration. Limit of detection (LOD) for MBH/SPOH@F and MBH/SPOH@NF were calculated to be 11 and 2.3 mg/dL, respectively. Moreover, MBH/SPOH@NF showed faster response (50 min) with respect to MBH/SPOH@F (60 min). Enhanced sensitivity of MBH/SPOH@NF comes from higher specific surface area and porosity of the nanofibers compared to the corresponding film. This led to more accessibility of H2O2 to SPOH molecules in the detection process. Finally, practical application of the ready-to-used and solid sensor was validated with the recovery of 94–97% in water resources.