Abstract:
Nanostructure composites of Fe3O4, ZrO2 and reduced graphene oxide (rGO) were synthesized using co-precipitation and sol-gel method for chemosensing Cr (VI) ions on the basis of fluorescence quenching. Pristine Fe3O4 and ZrO2, binary Fe3O4/ZrO2, metal oxide and rGO and ternary systems at ratios of 2:1:1and 2:2:1 was also synthesized. The phase purity, electronic and optical properties of the produced materials was investigated using Xray Diffractions (XRD), UV-Visible and FS. The XRD result shows, the average crystallite sizes for synthesized NMs estimated and found in order: B1 ˃ S2 ˃ S1 ˃ T ˃ B2. All are falls in the nano range except B2, UV-Visible result shows electron transition and fluorescence intensity for produced materials was obtained at λex/λem=248/502 nm by FS. In addition, FS reveals that fluorescence quenching of Fe3O4/ZrO2/rGO was observed in the presence of Cr (VI) ions due to IFE. The inner effect constant was calculated by modified Benesi–Hildebrand equation and Ka value is 0.492, approximated to 0.5 reveals that the emission–absorption stoichiometry is 1:1. The experimental condition such as solution pH and concentration was optimized for the application Fe3O4/ZrO2/rGO fluorescence chemosensor to probe Cr (IV) in aqueous solution. A good linear relationship between the concentration of Cr(VI) ions and increase fluorescent quenching was obtained in the linear concentration range from 50 to 250 ppm standard solution of Cr (VI) (R2 = 0.9917). Besides, the sensor exhibited a limit of detections 1.104 × 10-4 and sensitivity of 1.0313 × 10-4. Furthermore, the sensor achieved the selectivity towards Cr(VI) in an aqueous solution, and other competing metal ions such as Ni2+, Cd2+, Pb2+, Cu2+, Cr3+ and As2+ basically do not induced spectral change. The chemosensor was also tested for detection of Cr (VI) ion in environmental waste water sample. The result concentration 2.8, 2.7 and 3.6 ppm was obtained in direct contact with chemosensor in different volume of the waste water sample. Therefore, the developed Fe3O4/ZrO2/rGO fluorescence chemosensor can be a good candidate for selective detection of Cr (VI) in aqueous solution.
