Fluorescent Guar Gum-<i>g</i>-Terpolymer via In Situ Acrylamido-Acid Fluorophore-Monomer in Cell Imaging, Pb(II) Sensor, and Security Ink

Abstract

The nonconventional purely aliphatic scalable and reusable fluorescent guar gum (GRGM)-<i>grafted</i>-acrylic acid-<i>co</i>-3-(<i>N</i>-isopropylacrylamido)propanoic acid (NIPAPA)-<i>co</i>-<i>N</i>-isopropylacrylamide (GRGM-<i>grafted</i>-<b>1</b>, i.e., <b>2</b>), was synthesized via <i>grafting</i> of the optimum amount of GRGM and N-<i>H</i> 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 <b>2</b> 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 <b>2</b> elevated in concentrated solutions and solid state because of concentration-enhanced emission and aggregation-induced enhanced emission (AIEE) characteristics of <b>2</b>. Additionally, the emission efficiency of <b>2</b> elevated considerably with increasing GRGM contents and temperatures. The structure of <b>2</b>, 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 <b>2</b> were explored via density functional theory (DFT), time-dependent DFT, and natural transition orbital analyses. In solution, cyan light-emitting <b>2</b> 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.