Au-C/SiO2 nanocomposites with enhanced peroxidase-like activity for colorimetric and fluorometric detection of hydrogen peroxide

Gold nanoparticles with an average diameter of 10 nm have been facilely prepared on Cdots/SiO₂ nanocomposites by a photodeposition method to fabricate Au-C/SiO₂ nanocomposites. Photodeposited gold nanoparticles have shown commendable peroxidase-like activity, so they can oxidize 3,3',5,5'-tetramethylbenzidine effectually in the presence of H₂O₂. The catalytic reaction followed the Michaelis-Menton kinetics; the obtained K_m value of Au-C/SiO₂ nanocomposites with H₂O₂ is 60 times smaller than that of HRP, indicating the strong affinity of Au-C/SiO₂ nanocomposites to H₂O₂. In addition, Au-C/SiO₂ nanocomposites can be used for the fluorometric detection of H₂O₂ because photodeposited gold nanoparticles act as light absorbers of Cdots. The fluorescence of Au-C/SiO₂ nanocomposites was highly enhanced as much as 18 times at 7.5 mM of H₂O₂. Taken together, H₂O₂ can be detected quantitatively via dual-signal modes, colorimetric and fluorometric methods, with Au-C/SiO₂ nanocomposites. Thus, it is suggested that our Au-C/SiO₂ nanocomposites have a wide range of applications in bio-detection, catalysis, and clinical diagnostics.