Fluorescent Guar Gum-<i>g</i>-Terpolymer via In Situ Acrylamido-Acid Fluorophore-Monomer in Cell Imaging, Pb(II) Sensor, and Security Ink
Madhushree Mitra, Manas Mohan Mahapatra, Arnab Dutta, Mousumi Deb, Sayanta Dutta, Pijush Kanti Chattopadhyay, Subhasis Roy, Snehasis Banerjee, Parames C. Sil, Nayan Ranjan Singha
Abstract
The nonconventional purely aliphatic scalable and reusable fluorescent guar gum (GRGM)-grafted-acrylic acid-co-3-(N-isopropylacrylamido)propanoic acid (NIPAPA)-co-N-isopropylacrylamide (GRGM-grafted-1, i.e., 2), was synthesized via grafting of the optimum amount of GRGM and N–H functionalized in situ protrusion of acrylamido-acid fluorophore-monomer, i.e., NIPAPA, in multi C–C/N–C/O–C coupled solution polymerization of two non-emissive monomers in water. The intrinsically fluorescent noncytotoxic 2 envisaged the excellent potentials in sensing and removal of Pb(II), security ink, logic function, and imaging of both cancer and normal cells. The emission intensities of 2 elevated in concentrated solutions and solid state because of concentration-enhanced emission and aggregation-induced enhanced emission (AIEE) characteristics of 2. Additionally, the emission efficiency of 2 elevated considerably with increasing GRGM contents and temperatures. The structure of 2, in situ attached fluorophore-monomer, AIEE, cell-imaging ability, and the superadsorption mechanism were studied employing 1H/13C NMR, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, atomic absorption spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, dynamic light scattering, high-resolution transmission electron microscopy, fluorescence imaging, and fluorescence lifetime, along with measuring isotherms, kinetics, and thermodynamic parameters. The location, geometries, and electronic-structures of fluorophore, along with absorption and emission properties, of 2 were explored via density functional theory (DFT), time-dependent DFT, and natural transition orbital analyses. In solution, cyan light-emitting 2 envisaged an average 1.22 ns lifetime in CHCl3. The limit of detection and the maximum adsorption capacity were 2.94 × 10–7 M and 1100.25 mg g–1 at pH 7.0, 303 K, and 1000 ppm, respectively.