Nonenzymatic Hydrogen Peroxide Detection Using Surface-Enhanced Raman Scattering of Gold-Silver Core-Shell-Assembled Silica Nanostructures

Hydrogen peroxide (H₂O₂) plays important roles in cellular signaling and in industry. Thus, the accurate detection of H₂O₂ is critical for its application. Unfortunately, the direct detection of H₂O₂ by surface-enhanced Raman spectroscopy (SERS) is not possible because of its low Raman cross section. Therefore, the detection of H₂O₂ via the presence of an intermediary such as 3,3,5,5-tetramethylbenzidine (TMB) has recently been developed. In this study, the peroxidase-mimicking activity of gold–silver core–shell-assembled silica nanostructures (SiO₂@Au@Ag alloy NPs) in the presence of TMB was investigated using SERS for detecting H₂O₂. In the presence of H₂O₂, the SiO₂@Au@Ag alloy catalyzed the conversion of TMB to oxidized TMB, which was absorbed onto the surface of the SiO₂@Au@Ag alloy. The SERS characteristics of the alloy in the TMB–H₂O₂ mixture were investigated. The evaluation of the SERS band to determine the H₂O₂ level utilized the SERS intensity of oxidized TMB bands. Moreover, the optimal conditions for H₂O₂ detection using SiO₂@Au@Ag alloy included incubating 20 µg/mL SiO₂@Au@Ag alloy NPs with 0.8 mM TMB for 15 min and measuring the Raman signal at 400 µg/mL SiO₂@Au@Ag alloy NPs.