A novel needle microsensor measurement system was fabricated and applied to determine the concentration of dissolved oxygen. Platinum nanoparticles were employed to modify the surface of copper-core electrode in order to improve electrochemical response signal. The homemade electrode displayed efficient electrocatalytic reduction activity towards dissolved oxygen. The sensor responded linearly to dissolved oxygen in the range of 10
The reliable determination of dissolved oxygen in aqueous solution is of great importance in various applications such as environmental and industrial analysis [
With advances in electroanalytical chemistry and microelectronics technology, using microelectrodes as indispensable tools for evaluating chemistries has attracted particular attention in the past few years. In comparison with the conventional macroscale electrodes, microelectrodes have several advantageous characteristics such as rapid response, increased signal-to-noise ratio, low ohmic (
In this work, a needle microsensor was prepared and applied to detection of dissolved oxygen. Platinum nanoparticle (PtNP) which is one of the most researched noble metals was used to modify the surface of copper-core electrode in order to enhance electrochemically catalytic activity of the electrode. The tip of the electrode was characterized by stereomicroscope and scanning electron microscope (SEM), and the electrochemical performance of electrode was studied. The results showed that the homemade electrode with good electroreduction activity towards dissolved oxygen was successfully prepared. Furthermore, it can be used as a powerful tool for certain material testing at the level of cells or
Potassium hexachloroplatinate (K2PtCl6) was purchased from Sigma-Aldrich (USA). Copper enamelled wire (
The electrochemical measurements were carried out using a LK3200 electrochemical workstation (Tianjin Lanlike Chemical High Electronic Technology Co., LTD., China). A conventional three-electrode system, containing the PtNPs film modified self-made copper-core microelectrode (0.5 mm diameter) as a working electrode, a platinum wire (1 mm diameter) as a counter electrode, and an Ag/AgCl electrode (saturated with KCl) as a reference electrode, was employed for all electrochemical experiments.
Stereomicroscope images were obtained by using Olympus SZ61 instrument (Japan). Scanning electron microscope (SEM) images were gained by using Nova NanoSEM 430 instrument (Netherlands).
The fabrication of needle copper-core microelectrode (as shown in Figure
The fabrication of needle-tip microelectrode. (a) The structure diagram of microelectrode: 1: stainless steel syringe needle; 2: copper-core electrode (copper enamelled wire,
Before modification, the self-made copper-core microelectrode was ultrasonically cleaned with ethanol and double distilled water for 5 min to remove the contaminants. To enhance the catalytic activity of electrode, PtNPs were employed in this work. The microelectrode was immersed in 40 mL deposition solution (0.1 M PBS containing 10 mM K2PtCl6) and a constant potential at −0.2 V for 300 s was applied to obtain the PtNPs modified copper-core microelectrode.
Figure
Current
Figure
Stereomicroscope images of the tip of copper-core syringe needle. (a) Bare copper electrode section, (b) copper electrode section with PtNPs modification.
SEM images of PtNPs modified on the surface of microelectrode under different magnification.
As shown in Figure
(a) Cyclic voltammograms of PtNPs modified copper-core microelectrode in pH 7.0 O2-saturated PBS (A) and N2-saturated PBS (B). (b) Cyclic voltammograms of PtNPs modified copper-core microelectrode (A) and bare copper-core microelectrode (B) in pH 7.0 O2-saturated PBS.
Besides, virtually no current in the anodic sweep was obtained from curve A, indicating a totally irreversible process of dissolved oxygen reduction process. These results were in accordance with other reported electrochemical dissolved oxygen sensors [
Figure
Figure
Comparison of performance of various dissolved oxygen sensors.
Electrode | Detection limit ( |
Linear range | Reference |
---|---|---|---|
Nickel-salen/Pt | 22.2 | 0.12 mM–0.29 mM | [ |
CNF/GCE | 0.07 | 0.1 |
[ |
Vitamin B12/RDE | 9.2 | 15 |
[ |
0.6 | 6.3 |
[ | |
GNP/MWNTs-FeTMAPP/Au | 0.38 | 0.52 |
[ |
PtNPs/Cu-core microelectrode | 3.33 | 10 |
This work |
Simultaneous determination of dissolved oxygen at PtNPs modified copper-core microelectrode by cyclic voltammetry in 0.1 M PBS (pH 7.0); (a) reduction waves of the cyclic voltammograms and (b) calibration curve for dissolved oxygen.
For the purpose of the biological applications, the responses of common interferences on the proposed sensor were investigated and the results were summarized in Table
Interference effect on the detection of dissolved oxygen with the proposed sensor in PBS at pH 7.0 (applied potential: −0.3 V).
Species added | Response ratio (%) |
---|---|
Ascorbic acid | 4.8 |
Uric acid | 3.9 |
4-Aminophenol | 4.2 |
Ca2+ | 2.1 |
Na+ | 1.2 |
|
1.5 |
|
2.6 |
Hydroquinone | 4.9 |
Dissolved oxygen | 100 |
As we all know, the reproducibility and stability of electrode are also important parameters for evaluating the performance of a sensor. The device-to-device reproducibility was investigated from its response to dissolved oxygen saturated solution at five microelectrodes independently (Figure
(a) The reproducibility research of self-made microelectrode; (b) the stability of microelectrode stored at refrigerator temperature for two weeks in PBS (pH 7.0) with dropwise addition of 0.1 mM dissolved oxygen.
In the present work, a novel needle microsensor was prepared and can be applied to determine the concentration of dissolved oxygen. The tip of the microelectrode was polished on sand paper and polishing cloth, obtaining a smooth and flat surface. PtNPs were successfully electrodeposited on the surface of the self-control microelectrode. The resulting microsensor showed an excellent electrochemical property towards dissolved oxygen. Additionally, the current work exhibited a good potential for substances determination
The authors declare that there is no conflict of interests regarding the publication of this paper.
The financial supports from National Natural Science Foundation of China (Grant no. 81173204) and Application Basis and Advanced Technology Research Project of Tianjin (Grant no. 15JCQNJC10800) are acknowledged.