The oxidase-like activity of iridium nanoparticles, and their application to colorimetric determination of dissolved oxygen

Iridium nanoparticles (IrNPs) with intrinsic oxidase-like activity were synthesized by using sodium citrate as the stabilizer and NaBH 4 as the reducing agent. The IrNPs have an average diameter of 2.5 ± 0.5 nm and exhibit excellent oxidase-like property. Under the catalytic action of the IrNPs, 3,3′,5,5′-tetramethylbenzidine (TMB) is oxidized by dissolved oxygen (DO) to form a blue product with an absorption maximum at 652 nm. The catalytic activity is ascribed to the production of superoxide anion radical (O 2 ˉ∙). The chromogenic reaction is exploited for the determination of DO. The method exhibits a wide calibration range from 12.5 to 257.5 μM of DO and a limit of detection as low as 4.7 μM. Compared to other methods, this method presented here shows improved precision and faster response time. Iridium nanoparticles (IrNPs) stabilized by sodium citrate exhibit oxidase-like activity and can effectively catalyze dissolved oxygen (DO) by oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) to form a blue product.