Highly Sensitive Colorimetric Assay for Determining Fe³⁺ Based on Gold Nanoparticles Conjugated with Glycol Chitosan

Figure 6

(a) Photographic images of the color change of GC-AuNPs upon Fe³⁺ addition at various concentrations (1.8, 5.3, 8.9, 17.9, 53.7, 89.5, 125.3, and 179.0 μM from left to right) in the presence of 300 mM NaCl. (b) UV-Vis absorption spectra of GC-AuNPs upon addition of Fe³⁺ of various concentrations of Fe³⁺ (i.e., 1.8, 5.3, 8.9, 17.9, 53.7, 89.5, 125.3, and 179.0 μM) in the presence of 300 mM NaCl. (c) Absorption ratios (A₇₀₀/A₅₁₀) of Fe³⁺-GC-AuNP versus Fe³⁺ concentration in the presence of 300 mM NaCl (y = 0.02932x + 0.0077 (r² = 0.9896)).

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