Zhang and his group Au/Fe 3 O 4 /GO hybrid material for ultrasensitive detection
of Hg
2+ ions in an aqueous medium with the detection limit of 0.15 nM based on its
peroxidase mimics (Fig. 18) [85].
Darabdhara et al. reported the magnetic Au@Ni loaded on rGO nanocomposites
for colorimetric detection of phenolic compounds. Core-shell Au@Ni/rGO magnetically recoverable nanocomposites were prepared with size below 8 nm by a
solvothermal method which exhibited enzymatic behavior towards the colorimetric
detection and oxidation of TMB with LOD value 1.65 µM in range limit 1–
300 µM. They reported that the addition of different phenol concentration in
Au@Ni/rGO nanocomposite the colour changed from colorless to pink shown in
(Fig. 19) [86].
In similar process Yanzhou J. and his group have utilized the (rGO)/Cu 8 S 5 /polypyrrole (PPy) nanocomposites with Cu 8 S 5 nanoparticles and PPy layer decorated on
rGO sheets as peroxidase like activity for colorimetric detection of phenol and H 2 O 2 .
They reported that the synthesised (rGO)/Cu8S5/PPy nanocomposites exhibit higher
catalytic activity towards 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation in presence
of H 2 O 2 [87].
Liu Lu et al. reported that histidine capped gold nanoclusters (His@AuNCs) on
rGO sheets possessed oxidase-like activity, in presence of TMB to ox-TMB without
Fig. 17 a In the presence and absence of Cr(VI) ions UV-vis spectra of the ox TMB product,
b linear calibration plots for Cr(VI) detection, c absorbance of oxidized TMB in the presence of
50 nM of different ions (reproduced with permission from Ref. [84])
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