[23p-E104-1~16] 12.6 Nanobiotechnology

▲ [23p-E104-14] EIS Charge Transfer Enhancement by the Electrochemical Mediator “Methylene Blue”

〇Huanwen Han^1,2, Ting-Chieh Chu¹, Ichiro Yamashita¹ (1.Osaka Univ., 2.NFHD Corp.)

Keywords:Methylene Blue, Charge Enhancement

Electrochemical Impedance Spectroscopy (EIS) is a method wildly used for interface measurement. This has great potential for biomolecular detection due to the capacity to operate under high salt conditions. The impedances monitor the charge-transfer between electrode and electrochemical redox probes. Amplifying the charge-transfer process will achieve high measurement performance.^[1] The selection of redox probe depends on various parameters, among which 1 - 10 mM [Fe(CN)₆]^3-/4 is the most frequently chosen in EIS experiments, and we use this redox pair as well. We have discovered that adding a small amount of second redox probe could enhance the charge transfer between electrode and hexacyanoferrate strongly, as [Ru(bpy)₂DPPZ]²⁺. We change the Ru complex to methylene blue and carry out the EIS measurement and found a similar effect. The EIS were measured with commercial glassy carbon electrode and the electrolyte was PBS with 1 mM K₃[Fe(CN)₆] /K₄[Fe(CN)₆]. After stabilization, we added the MB from 0.01 mM, 0.05 mM, 0.1 mM, 0.5 mM, 1 mM, and 2 mM in sequence. Figure 1 shows the result of the Nyquist plot. After increasing the MB concentration to 0.5 mM, very small semicircles are shown on the plot and the Rct is almost no change with concentration increase. This phenomenon looks like occur in a wide range of electrodes and DNA intercalator and need more studies to clear.