title: Off-on Fluorescent Sensor from On-off Sensor: Exploiting Silver Nanoparticles Influence on the Organic Fluorophore Fluorescence.
abstract: Turn-off fluorescence of organic fluorophore, 2-{[4-(2H-Naphtho[1,2-d][1,2,3]triazol-2-yl)-phenyl]carboxylic acid (NTPC), with metal ions (Fe(3+), Cu(2+), Pb(2+)) was converted into turn-on fluorescent sensor for biologically important Zn(2+), Cu(2+) and Fe(3+) metal ions in aqueous solution at ppb level by exploiting strong fluorescence quenching phenomena of metal nanoparticles when organic fluorophores assembled in the vicinity of metallic surface. Amino acid attached phenolic ligands (L) were used as reducing as well as functional capping agents in the synthesis of silver nanoparticles (AgNPs). The hydrogen bonding functionality of L facilitated the assembling of NTPC in the vicinity of metallic surfaces that leads to complete quenching of NTPC fluorescence. The strong and selective coordination of L with metal ions (Zn(2+), Cu(2+) and Fe(3+)) separates the NTPC from the AgNPs surface that turn-on the NTPC fluorescence. HR-TEM and absorption studies confirm the metal coordination with L and separation of NTPC from the AgNPs surface. Mn(2+) showed selective red shifting of NTPC fluorescence after 12 h with all sample. Effects of different amino acid attached phenolic ligands were explored in the metal ion sensitivity and selectivity. This approach demonstrates the multifunctional utility of metal NPs in the development of turn-on fluorescence sensor for paramagnetic heavy metal ions in aqueous solution. ᅟ
authors.affiliation: School of chemical & Biotechnology, SASTRA University, Thanjavur, 613 403, Tamil Nadu, India.
authors.forename: P S
authors.initials: PS
authors.lastname: Hariharan
authors.affiliation: School of chemical & Biotechnology, SASTRA University, Thanjavur, 613 403, Tamil Nadu, India.
authors.forename: Arvind
authors.initials: A
authors.lastname: Sivasubramanian
authors.affiliation: School of chemical & Biotechnology, SASTRA University, Thanjavur, 613 403, Tamil Nadu, India. philip@biotech.sastra.edu.
authors.forename: Savarimuthu Philip
authors.initials: SP
authors.lastname: Anthony
mesh_terms: D066241:Carbon-13 Magnetic Resonance Spectroscopy; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006860:Hydrogen Bonding; D053768:Metal Nanoparticles; D046529:Microscopy, Electron, Transmission; D033362:Powder Diffraction; D066244:Proton Magnetic Resonance Spectroscopy; D012834:Silver / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
chemical_list: D005456:Fluorescent Dyes; D012834:Silver
keywords: Heavy metal ions sensor; Nanoparticles-organic fluorophore hybrid sensor; Supramolecular chemistry; Turn-on fluorescent sensor fabrication