An unusual "off-on" fluorescence sensor for iron(III) detection based on fluorescein-reduced graphene oxide functionalized with polyethyleneimine

Polyethyleneimine (PEI)-modified reduced graphene oxide (rGO) based fluorescent sensor is reported for metal-ion sensing. PEI-rGO nanocomposites are synthesized by a facile and controllable method using hydrazine hydrate as a main reducing agent and PEI that is a reducing agent, surface modifier and polymer host. The formation of PEI-rGO nanocomposites is confirmed with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-vis spectroscopy, Zeta potential measurements and Dynamic Light Scattering (DLS) analysis. Afterward, the interaction of fluorescein (FL) with PEI-rGO nanocomposites in aqueous dispersion, leading to the formation of FL/PEI-rGO ternary system, are studied at various conditions by using UV-vis absorption, steady-state and time-resolved fluorescence spectroscopies. It is observed that the photophysical properties of FL are dependent on the amount of both FL and PEI-rGO nanocomposites. The sensing ability of FL/PEI-rGO ternary system are examined in the detection of metal ions as a fluorescent sensor. The spectroscopic data reveal that the FL/PEI-rGO ternary system shows high sensitivity and selectivity for Fe3+ ions in aqueous solution. The detection limit for Fe3+ are determined to be 1.12 mu M. (C) 2016 Elsevier B.V. All rights reserved.