A novel modification method via in-situ reduction of AuAg bimetallic nanoparticles by polydopamine on carbon fiber microelectrode for H2O2 detection

In this work, a facile in-situ reduction method was developed for the modification of carbon fiber microelectrode (CFME) to build novel electrochemical sensors for the detection of H 2 O 2 . The polydopamine (PDA) was employed as the surface modification material for one-step decoration of AuAg bimetallic nanoparticles through in-situ reduction on the surface of PDA/CFME. Compared to Au-PDA/CFME and Ag-PDA/CFME, 2Au1Ag-PDA/CFME (immersed PDA/CFME in AgNO 3 for 1 h, HAuCl 4 •4H 2 O for 2 h in order) exhibited higher electrocatalytic activity toward H 2 O 2 sensing due to bimetal synergism. Under the optimal condition, the 2Au1Ag-PDA/CFME appeared a wide linear range of 0 μM - 55 μM (R 2  = 0.990), 55 μM – 2775 μM (R 2  = 0.991) with high sensitivity (12966 μA mM −1 cm −2 , 0–55 μM; 2534 μA mM −1 cm −2 , 55–2775 μM), and low detection limit (0.12 μM). Furthermore, good selectivity and repeatability of 2Au1Ag-PDA/CFME favored its applications in biological samples, especially in cellular level. The detection of H 2 O 2 released from HepG2 living cells was realized by applying 2Au1Ag-PDA/CFME, indicating a potential usage of the fabricated electrode for H 2 O 2 detection in cancer cells. In addition, the above simple in-situ reduction method based on PDA's adhesion and reducibility offered a universal strategy to decorate noble metals onto microelectrode for different application in the future.