Fluorescent Terpolymers Using Two Non-Emissive Monomers for Cr(III) Sensors, Removal, and Bio-Imaging

Abstract

The nonconventional purely aliphatic intrinsically fluorescent multifunctional terpolymers, such as 2-acrylamido-2-methylpropane sulfonic acid-co-2-(3-acrylamidopropylamido)-2-methylpropane sulfonic acid-co-acrylamide (AMPS-co-APMPS-co-AM, 1), acrylic acid-co-3-acrylamidopropanoic acid-co-acrylamide (AA-co-APA-co-AM, 2), and methacrylic acid-co-3-acrylamido-2-methyl propanoic acid-co-acrylamide (MAA-co-AMPA-co-AM, 3), were synthesized via N-H functionalized multi-C-C/N-C coupled in situ attachments of fluorophore monomers, that is, APMPS, APA, and AMPA, in solution polymerization of two non-fluorescent monomers. These terpolymers were suitable for selective Cr(III) sensors, high-performance exclusions of Cr(III), and fluorescence imaging of human osteosarcoma cancer cells. The structures of 1, 2, and 3, in situ attachments of fluorescent amino acid monomers, locations of fluorophores, aggregation-induced enhanced emissions, and the superadsorption mechanism were understood via microstructural analyses. The geometries, electronic structures, and the low-lying singlet-singlet absorption and emission of 1, 2, and 3 were explored using density functional theory (DFT), time-dependent DFT, and natural transition orbital analyses. The ionic and variable interactions of 1, 2, and 3 with Cr(III) were envisaged via analyses of adsorbed microstructures, fitting of kinetics data to a pseudo-second-order model, and the measurements of activation energies. For 1/2/3, limit of detection values and adsorption capacities were 1.88 × 10-7/3.75 × 10-7/1.25 × 10-7 M and 1316.35/1431.40/1372.18 mg g-1, respectively, at pHi = 7.0, 303 K, and 1000 ppm. The better overall properties made 3 to be more suitable in sensing and cell imaging.