Au₂₅ Nanoclusters Exhibit Superhigh Catalytic Activity in Electrochemical Detection of As(III)

An atomic-level Au nanocluster, as an excellent photocatalyst, is generally not considered as an efficient electrocatalyst due to its poor stability. Herein, a method is proposed to stabilize abundant Au₂₅ on Fe₂O₃ nanoplates (Au₂₅/OV-Fe₂O₃) successfully with oxygen vacancies (OV) created. Au₂₅/OV-Fe₂O₃ shows superhigh catalysis in the electrochemical reduction toward As(III). The record-breaking sensitivity (161.42 μA ppb^-1) is two orders of magnitude higher than currently reported, where an ultratrace limit of detection (9 ppt) is obtained, suggesting promising applications in the analysis of organic and bioactive substances. The stability of Au₂₅ is attributed to the Au-Fe bond formed after loading Au₂₅ nanoclusters on Fe₂O₃ nanoplates through "electron compensation" and bond length (Au-S) shortening. Moreover, the ligand S atoms in Au₂₅ nanoclusters significantly contribute to the reduction of As(III). The fantastic stability and superior catalytic ability of Au₂₅/OV-Fe₂O₃ provide guidelines to stabilize Au nanoclusters on metal oxides, indicating their potential electroanalytical applications.