Hollow Co₃O₄ nanospheres modified with RuCl₃ as peroxidase mimics for sensitive determination of sulfide ions at neutral pH

Developing high-performance nanozymes at neutral pH is extremely necessary for the application of biological and water environmental systems. RuCl₃-modified hollow Co₃O₄ nanospheres (Ru³⁺-Co₃O₄ HNSs) were utilized to establish a colorimetric sensor for selective determination of sulfide ions (S²⁻). The hollow Co₃O₄ nanospheres after doping of Ru³⁺ provide a large surface area and more active sites, thereby boosting the electron transport and the affinity to the substrates. Specifically, the as-prepared Ru³⁺-Co₃O₄ HNSs exhibited remarkable peroxidase-like (POD-like) activity, which can catalyze colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB under neutral pH conditions. Furthermore, the Ru³⁺-Co₃O₄-based colorimetric sensor achieved a wide linear range (0.5-20 μM) and a low detection limit (0.051 μM) for S²⁻ ion concentration, as well as good selectivity, reproducibility and practicability in sewage water. This research aims to boost the accuracy of S²⁻ detection and shed light on application prospects in the water environmental fields.