Presentation

1. Methods for improving the
sensitivity of microelectrodes
2023-3-24
Presenter : Mohsin Bashir
Team members: Wang Zi Liang, Cheng He Peng, Mohsin Bashir

2. CONTENTS
1
2
3
4
How to improve microelectrode sensitivity
Microelectrode - definition and applications
Applications of highly sensitive microelectrodes
Problems with microelectrode sensitivity and low sensitivity

3. Microelectrode - definition and applications
01

4. Part I: Microelectrode definition and application manufacturing
Definition
Microelectrode refers to an electrode
with at least one dimension of the
electrode in the micrometer or
nanometer size, and its working area is
very small, and the limit of the electrode
area size is not very strict.
The sensitivity of microelectrodes refers to
their ability to detect and measure small
changes in a target parameter, such as
electrical potential, pH, or concentration of
a specific ion or molecule.
Sensitivity Meaning

5. Part I: Microelectrode definition and application manufacturing
Microelectrode type
 Ultramicro disc electrode, ultramicro circular electrode, ultramicro cylindrical electrode,
ultramicro spherical electrode, ultramicro semi-flat spherical electrode, ultramicro ribbon
electrode, ultramicro array electrode, ultramicro forked finger electrode and powder micro
electrode, etc.
Brush electrode
Micro column electrode

6. Part I: Microelectrode definition and application manufacturing
Microelectrode characteristics
 Due to the extremely small electrode surface of the microelectrode, its electrochemical
properties have many unique advantages that conventional electrodes do not have. On the
other hand, because the microelectrode itself is also very small, it can be inserted into
animals for real-time, in vivo continuous analysis, and directly obtain in vivo chemical
activity information, which has gained important applications in life science research.

7. Part I: Microelectrode definition and application manufacturing
Microelectrode applications
 Potassium and sodium ion analysis : Potassium and sodium ions are several major ions necessary for the
maintenance of normal life activities, and are also some of the most abundant cations in human body fluids.
 In vivo pH measurement∶ In the course of life activities. Acidic and alkaline metabolites are continuously
produced in the organism.
 Analysis of calcium ions and other substances : Calcium is abundant in the human body, but trace amounts of
calcium ions in body fluids have important physiological roles. For example, calcium acts as an activator and
inhibitor of enzymes.
 There are also many applications of microelectrodes for the determination of various other ions.
 Micro-electrodes are being used in various fields including neuroscience, electrochemistry, and biosensors.

8. Microelectrode sensitivity and the problems that exist with low sensitivity
02

9. Why improve microelectrode sensitivity
Reason
The detection environment during the
experiment is complex, there are external
disturbances, the detection technique is very
difficult, and the finger-end effect and edge
effect increase significantly as the electrode
size decreases. All these reasons can affect the
accuracy of the experiment.

10. How to improve microelectrode sensitivity
03

11. Part III: Methods to improve the sensitivity of microelectrodes
Here are a few strategies to improve microelectrode sensitivity:
1. Decrease the electrode size (sensitivity ∝ surface area/volume)
2. Increase surface area (nano-particles or nano-wires)
3. Improve the electrode material (low impurities → low impedance and noise) (High electron transfer rate -
gold)
4. Reduce the electrode noise (external electromagnetic interference)
5. Improve the electrode surface (biological or chemical coating → good for certain molecules)
6. Optimize electrode geometry (sharp or pointing electrodes)

12. Part III: Methods to improve the sensitivity of microelectrodes
Firstly, in order to improve the electrode performance of the glassy carbon electrode, it should be pretreated before
use.
Then, the rGo/AuNPs GCE was prepared by a two-step electrodeposition method as follows.
In the first step, the reduced graphene oxide modified glassy carbon electrode (rGO GCE) was prepared by
constant potential deposition method.
In the second step, reduced graphene oxide nanogold modified glassy carbon electrode (rGO/AuNPs GCE) was
prepared by cyclic voltammetry.
Reduced graphene oxide nanogold-modified glassy carbon electrode

13. Part III: How to improve microelectrode sensitivity
Reduced graphene oxide nanogold-modified glassy carbon electrode
The peak current of bare GCE
(curve a) is 46.5 μA, and the peak
current of rGo/AuNPs GCE
(curve b) is 164.9 μA.
The RCT (charge transfer
resistance) of the bare GCE
(curve a) is 117 Ω and the RCT
of the rGo/AuNPs GCE (curve b)
is 57 Ω.
The performance of the modified
glassy carbon electrode is higher
than that of the normal one due to
the high electrical conductivity of
the composite and the high
specific area that increases the
electron transfer rate.
Cyclic voltammetric curves Electrochemical AC impedance
spectroscopy

14. Application of high-sensitivity microelectrodes
04

15. Part IV: Application of high-sensitivity microelectrodes
Platinum microelectrodes for the detection of serotonin concentrations
 The platinum microelectrode is placed in a
solution of platelets to be tested and the
platelets are detected by a current-time
curve. When platelets collide with the
platinum microelectrode, the serotonin in
the platelets is oxidized and the reaction
generates an anodic current. Since the
platinum microelectrode has a very high
sensitivity, the current signal can then be
captured. This spike-type current is caused
by the electrochemical reaction of the
colliding particles, while the peak anodic
current can be integrated to calculate the
concentration of serotonin in the platelets.

16. Part IV: Application of high-sensitivity microelectrodes
Gold microelectrodes for the detection of redox substances
 The left figure shows the collision process of a
single emulsion oil droplet on a gold microelectrode.
The electrochemical effect of electrolysis within a
single emulsion droplet can be observed by applying
an appropriate potential to the gold microelectrode
and performing a current-time curve test. Due to the
complete electrolysis of all redox substances within
the droplet, a spike-like response can be observed in
each current-time curve response.

17. Thank you