Graphene Oxide-terpyridine Conjugate: A Highly Selective Colorimetric and Sensitive Fluorescence Nano-chemosensor for Fe^2+ in Aqueous Media

A graphene oxide-terpyridine conjugate (GOTC) based colorimetric and fluorescent nano-chemosensor was synthesized. It showed high selectivity and sensitivity for Fe^2+ and Fe3+ ions in neutral aqueous solution over other metal ions such as Li+, Na+, Ba^2+, Ca^2+, Al3+, Cd^2+, Co^2+, Cu^2+, Hg^2+, Mn^2+, Ni^2+, Pb^2+, Zn^2+, Cr3+ and Ag+. In absorption spectra, upon addition of Fe^2+ or Fe3+, the sensor displayed a peak at 568 nm, by changing the color of the solution from light pink for GOTC to light magenta and deep magenta for Fe3+ and Fe^2+, respectively. Also, the fluorescence studies revealed that, Fe^2+, Fe3+ and Co^2+ quench the emission of GOTC at 473 nm, while other metal ions do not quench the fluorescence of GOTC in solution. Colorimetric and fluorescence techniques could be used for detection of Fe^2+ ion concentration at least about 6-10 μM in water solution. The sensing on test paper was also investigated for the nakedeye detection of Fe^2+.