Fig. 15 Compared with other ions, the selectivity of the Au nanoparticles for colorimetric
detection of Cr(III) and Cr(VI). Image of (a, c, e) various ions in the absence of masking agents, in
presence of citrate and thiosulfate, with EDTA; UV spectra of the Au nanoparticles for Cr(III) and
Cr(VI) (b, d, f) other ions in the absence of masking agents, in presence of citrate and thiosulfate,
with EDTA (reproduced with permission from Ref. [82])
Fig. 16 a–c UV spectra of oxidation of TMB as prepared Ag-CoFe 2 O 4 /rGO NPs (reproduced
with permission from Ref. [83])
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