A smartphone-based colorimetric PET sensor platform with molecular recognition via thermally initiated RAFT-mediated graft copolymerization

In this work, we report a low-cost and easy-to-use molecularly-imprinted colorimetric sensor platform that can sense target analyte with high sensitivity and good selectivity. The platform has been examined for colorimetric detection and quantitation of a model textile dye, basic red 9 (BR9), by employing methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA) and cumyl dithiobenzoate (CDB) as functional monomer, crosslinker and RAFT agent, respectively. Benzophenone (BP), a photoinitiator, was covalently immobilized on the surface of poly(ethylene terephthalate) (PET) and then thermally activated by homolytic cleavage to form radicals on the surface that initiate RAFT-mediated grafting of a thin recognition layer. The molecularly imprinted polymer (MIP) layer of about 100 nm showed excellent removal of 76.7% target dye in 10 min and high selectivity compared to other similar dyes with an imprinting factor of 10.31 in the competitive environment. The resulting MIP grafted PET substrate was efficiently used as recognition unit in a smartphone-based colorimetric detection method using a color adaptation algorithm for point-of-care applications. Based on the obtained performance, it is promising to use the method for the detection and quantification of various analytes with chromophores.