Figure 1.
Schematic illustrations of PET from TAPP to GO sheets, and iron (III) ions selectively obstructing the process of PET.
Figure 2.
Fluorescence and absorption spectra recorded during addition of different concentrations of GO suspension to TAPP solution.
The inset in Figure 2a shows that the variation of fluorescence intensity of TAPP at 645.0 nm varies with the increasing concentrations of GO. Concentrations: TAPP, 2.4 µM; GO from curve 2 to 12 (µg ml−1), 2.0, 4.0, 8.0, 12.0, 16.0, 20.0, 22.0, 24.0, 26.0, 28.0, 30.0. λex, 413.0 nm. The inset in Figure 2b shows that the variation of maximum absorption wavelength (λmax) of TAPP varies with the addition of GO. Concentration: TAPP, 2.4 µM; GO from curve b to i (µg ml−1), 2.0, 4.0, 8.0, 12.0, 16.0, 20.0, 24.0, 26.0. pH, 4.1.
Figure 3.
Fluorescence and absorption spectra recorded during addition of different concentrations of RGO suspension to TAPP solution.
The inset in Figure 3a shows that the variation of fluorescence intensity of TAPP at 645.0 nm varies with the increasing concentrations of RGO. Concentrations: TAPP, 2.4 µM; RGO from curve 2 to 10 (µg ml−1), 2.2, 4.5, 6.8, 9.0, 11.2, 13.5, 15.8, 18.0, 22.5. λex, 413.0 nm. The concentration of RGO from curve b to f in Figure 3b (µg ml−1), 2.2, 4.5, 6.8, 9.0, 13.5. pH, 4.1.
Figure 4.
AFM images of GO, TAPP/GO complex and that in presence of iron (III) ions on mica substrate together with section analysis along the scored line.
(a) GO; (b) TAPP/GO complex; (c) TAPP/GO complex in presence of iron (III) ions. Concentration: GO, 16.0 µg ml−1; TAPP, 2.4 µM; iron (III) ions, 8.0 µM.
Figure 5.
Fluorescence and absorption spectra recorded during addition of the increasing concentrations of iron (III) ions to TAPP/GO complex solution.
The inset in Figure 5a shows that the enhanced fluorescence intensity at 645.0 nm varies with the increasing concentrations of the iron (III) ions. Concentration: TAPP, 2.4 µM; GO, 16.0 µg ml−1; iron (III) ions from curve 2 to 17 (µM), 0.3, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0, 8.0, 10.0, 13.0, 15.0, 20.0, 30.0, 40.0, 50.0, 60.0. λex, 413.0 nm. The inset in Figure 5b is to intuitively display the blue-shift of Soret band of TAPP in GO-bound state with the addition of increasing concentration of iron (III) ions. Concentration: TAPP, 2.4 µM; GO except for curve a (µg ml−1), 16.0; iron (III) ions from curve c to j (µM), 0.3, 0.8, 1.0, 2.0, 4.0, 5.0, 8.0, 13.0. pH, 4.1.
Figure 6.
Fluorescence spectra of the TAPP, TAPP/RGO complex and that in presence of iron (III) ions.
Concentrations: TAPP, 2.4 µM; RGO, 13.5 µg ml−1; iron (III) ions, 60.0 µM. λex, 413.0 nm, pH, 4.1.
Figure 7.
XPS wide-scan survey of the fresh obtained TAPP/GO (black line) and TAPP/RGO (red line) complexes exposed to the contained iron (III) ions solution, respectively.
Inset shows detailed XPS survey of the Fe 2p region.
Figure 8.
Time-resolved fluorescence Decays of the TAPP and TMPyP recorded at different GO concentrations and iron (III) ions.
Concentration: TAPP, 2.4 µM, TMPyP, 3.0 µM; GO from curve b to i (µg ml−1), 8.6, 13.0, 17.3, 21.6, 21.6, 21.6, 21.6, 21.6, 21.6; iron (III) ions from curve f to i (µM), 2.0, 4.0, 8.0, 16.0. pH, 4.1.
Figure 9.
Fluorescence response of TAPP/GO complex to various metal ions.
Concentration: TAPP, 2.4 µM; GO, 16.0 µg ml−1; iron (III) ions, 15.0 µM; Other metal ions were all 30.0 µM. All data were collected at 645.0 nm.
Table 1.
Determination of iron (III) ions in the iron-contained protein and human serum sample using the proposed method and AAS.