Pt–Se nanostructures with oxidase-like activity and their application in a selective colorimetric assay for mercury(II)

In this paper, platinum (Pt)–selenium (Se) nanostructures and Pt nanoparticles were synthesized by a facile one-step chemical reduction route and their catalytic performance was evaluated as oxidase mimic. The results of structure characterization revealed that Pt – Se nanostructures consist of Pt and Se atoms (the Pt/Se atomic molar ratio is approximately 7:3), while Pt nanoparticles consist of pure element Pt. The oxidase-like activity of Pt – Se nanostructures and Pt nanoparticles was evaluated with 3,3′,5,5′-tetramethylbenzidine (TMB) as substrate. The results indicated that Pt – Se nanostructures had a lower Michaelis constant ( K m ) and higher catalytic constant ( K cat ) for TMB oxidation than that of Pt nanoparticles,which mean the binary Pt – Se hybrid nanostructures had stronger binding affinity with TMB and higher catalytic activity in comparison with monometallic Pt nanoparticles. The enhanced oxidase-like activity of Pt – Se nanostructures may be due to element Se doped in binary Pt – Se hybrid nanostructures, which can accelerate electron transport and provide excellent chemical stability against catalytic performance degradation during the TMB oxidation reaction. Mercury (II) ions (Hg 2+ ) could inhibit the oxidase mimetic activity of Pt – Se nanostructures and resulted in a color change of the reaction system. Based on this mechanism, a facile colorimetric assay for Hg 2+ was developed with a detection limit as low as 70 nm and a linear range of 0–2.5 μM.