̸ּҺ

亯

PUBLICATION
 
 
  19 Frequency-Distance Responses in SECM-EQCM : A Novel Method for Calibration of the Tip-Sample Distance.
ۼ  WizAMC ۼ  2015-07-20
÷    ȸ  1434
 

19 Frequency-Distance Responses in SECM-EQCM : A Novel Method for Calibration of the Tip-Sample Distance.
Myoungsun Shin and Il Cheol Jeon.  Bull. Korean Chem. Soc. 1998, Vol. 19, No. 11

 

Fig1. (A) The current response obtained while the tip electrode of 11 um diameter is approaching the gold and (B) the corresponding frequency measured concurrently. They were obtained in a 5mM [Os(bpy)3]2+ solution in 0.05 M H2SO4 while the tip electrode and the gold substrate electrode were kept at 0.85 and 0.20 V, respectively. The gap distance marked in the Figure was estimated based on the theoretical curve. (Inset) It shows the expanded frequency (empty circles) and current (filled circles) curves near the zero separation. Tip approach speed : 0.05 um/s

 

 

Fig 2. The frequency responses monitored using the tip electrode of 11um diameter in (A) air, (B) water, (C) and acid solution, and (D) a mediator complex solution ([Os(bpy)3]2+) with no electrical connection to the tip. The gap distance marked in Figure was attained assuming a point of the frequency increase as the Origin. Other conditions are the same as in Figure 1.

 

 

Fig 3. The frequency response monitored while an STM tip is approaching a bare gold electrode in air. The substrate was grounded and the tip potential was 0.1V with a feedback resistor of 100k. The gap distance marked in figure was attained assuming the onset point of abrupt current change as the orging. Other donditions are the same as  in Figure 1.

 

 

Fig4. The current response obtained while the tip electrode of 11 um diameter approacing the gold substrate and the corresponding frequency measured concurrently (empty circles). RG value for this tip electrode is cca. 3 and a resistor of 10 M was used in the feedback loop of the current-to-voltage converter to measure larger cM [urrent at a close range. They were obtained In a 5 mM [Os(bpy)3]2+ solution in 0.05 M H2SO4 while the tip electrode and the gold substrate electrode were kept at 0.85 and 0.20 V, respectively. The gap distance marked in figure was estimated based on the theoretical curve. That is the separation between the tip and substrate at I_T/I_T.inf=11.5 is estimated as 0.4 um while the frequency response (empty circles in the inset) shows the contact point near 0.35 um. Other conditions are the same as in Figure 1.

 

 

Fig5. (A) The current response obtained while the tip electrode of 11 um diameter is approaching the Nafion coated electrode on gold substrate in 0.05 M H2SO4 and (B) the corresponding frequency measured concurrently. The gap distance marked was attained assuming a point of frequency increase as the origin. Other conditions are the same as in Figure 4

 

 

Fig 6. (A) The current response obtained while the tip electrode of 11um diameter is approaching the [Os(bpy)_3]^2+ loaed Nafion coated electode on gold substrate and (B) the corresponding frequency measured concurrently. These were measured after the Nafion film used in recording Figure 5 was loaded with [Os(bpy)_3]^2+ performed by adding [Os(bpy)_3]^2+ to 0.05 M H2SO4 without disturbing the arrangement. They were  obtained in a 0.2 mM [Os(bpy)_3]^2+ solution in 0.05 M H2SO4. Other conditions are the same as in Figure 4

 

 


 

Fig 7. (A) The current response obtained  m a 5 mM [Os(bpy)_3]^2+ solution while the tip electrode of 11um diameter is approaching the [Os(bpy)_3]^2+ loaed Nafion coated electode on gold substrate and (B) the corresponding frequency measured concurrently. The Nafion film used in recording Figure 6 was used after adding extra [Os(bpy)_3]^2+  to 0.05 M H2SO4 without disturbing the arrangement. Other conditions are the same as in Figure 4.

 


 


 


 


 

 
Top