CoOOH/Au nanocomposite with enhanced peroxidase-like activity for colorimetric sensing of hydrogen peroxide

In this study, a novel CoOOH/AuNPs nanozyme was synthesized through a two-step process by integrating gold nanoparticles (AuNPs) with cobalt oxyhydroxide (CoOOH) nanosheets. The CoOOH/AuNPs nanozyme exhibits significant oxidase and peroxidase (POD)-like activities, with a marked enhancement in POD-like activity attributed to the presence of AuNPs. This advancement facilitates the catalytic decomposition of hydrogen peroxide (H 2 O 2 ) into hydroxyl radicals (·OH), which subsequently oxidizes 3,3′,5,5′-tetramethylbenzidine (TMB) to form blue oxidized TMB (ox-TMB) with an absorbance peak at 652 nm. The CoOOH/AuNPs nanozyme's stability was evaluated and was found to be superior to that of natural horseradish peroxidase (HRP), maintaining over 90 % activity after a 30-day period at room temperature. Steady-state kinetic studies confirmed the nanozyme's higher affinity and quicker reaction rate for the TMB substrate compared to HRP. The POD-like catalytic mechanism was investigated, highlighting the essential role of ·OH in the catalytic reaction. A colorimetric sensing platform was then fabricated for H 2 O 2 detection in chicken feet with pickled peppers, demonstrating high sensitivity and selectivity. This study presents a significant advancement in the field of nanozyme-based sensors for food safety applications.