Covalent Immobilisation of a Nanoporous Platinum Film onto a Gold Screen-Printed Electrode for Highly Stable and Selective Non-Enzymatic Glucose Sensing

Round 1

Reviewer 1 Report

The sensor propagated a rapid response time < 5 seconds and exhibited a wide linear range from 1 mM to 18 mM. What happens in concentrations greater than 18 millimoles?

I ask those questions in order to fully understand the work.
I have loved reading your work and trying to correct it.
It is very well posed, written and explained
It deserves and should be published in catalysis.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors showed a composite electrode, which is Au-MPTS-Pt composite material. It shows high reproducibility, high selectivity, and high stability. Some improvements were achieved in this study. Nevertheless, there still remain some problems to be dealt with before publication.

 

1. In the abstract, it says that “Progress in development of commercially available non-enzymatic glucose sensors continues to be problematic due to issues regarding selectivity, reproducibility and stability.” --> However, the reproducibility and stability are not true compared to the enzymatic glucose sensors. The non-enzymatic ones perform better reproducibility and stability than the enzymatic ones. Besides, these are not the greatest problems in the non-enzymatic glucose sensor.
2. Figure 1 caption: “……l in 0.5 H₂SO₄ at a scan rate……” --> What is the unit of 0.5?
3. In section 2.1, it reads: “The voltammetric response of the gold electrode in 0.5 M sulphuric acid has two distinct peaks, shown in Figure 1 corresponding to oxide formation on the gold surface during the positive sweep, and removal of the oxide layer when reversing the scan direction.” --> Authors mention “two distinct peaks”; however, there are many oxidation peaks in the positive scan. It is necessary to explain this.
4. Follow Question #3, the areas in the positive scan and negative look different. Why? Besides, if the electrode is just Au, the CV curve in the positive scan should be simple.
5. The authors mentioned 2d-netwrok in section 2.2. It is necessary to define what is “2d-network”. Does this mean 2-dimension? If yes, the configuration of the silane units does not seem to be just 2-dimension.
6. From lines 132 to 133, it reads: “These rf values indicate a significant increase in the surface area of immobilised platinum nanoparticles after 300 cycles when compared to that recorded after 100 cycles.” --> The reason for the increment of the current is not well explained. It should be explained in detail.
7. From line 133-137, it reads: “Recent studies have demonstrated that nanoporous platinum surfaces delivers many advantages including, a stable self-supporting nanometer sized structure coupled with increased catalytic activity and selectivity for glucose due to high surface area of the porous surface.” --> Follow Question #6, the increment of the current density is still not explained. Besides, since authors mentioned “Recent studies have demonstrated that…” --> References are necessary.
8. In Figure 1, are the authors sure that the scan rate is 0.1 mV s^-1 or 0.1 V s^-1. Please check.
9. In Figure 3, the morphology of the Au electrode changed significantly after 300 cycles of the scan. Why? It is not explained in detail in section 2.2.
10. Follow Question #9, are the authors sure that the electrode is pure Au in Figure 3? The specimens shouldn’t be the Au-MPTS-Pt electrodes (i.e., like Figure 2)?
11. The information in Figure 4 is not clear. It is necessary to enlarge the spectrum.
12. Lines 111-114 say: “Chemisorption of a nanoporous platinum surface onto the MPTS 2d-network was performed by electrochemical co-deposition of a platinum-copper alloy and the subsequent electrochemical dealloying of the less noble copper using a previously described method.” --> Why the co-deposition of a platinum-copper alloy was conducted instead of pure Pt deposition.
13. Follow Question #12, the authors only mention Pt in the abstract and introduction; however, Cu suddenly came out in the results and discussion part. These should be revised greatly. This makes the manuscript inconsistent.
14. Follow Questions #11 and #12, it seems that the electrodes contained quite a large amount of Cu. It might also affect the performance of the electrode. It is not convincible to say that the electrodes are composed of Pt and Au metals.
15. In Figure 2, CVs were conducted in H₂SO₄, however, in Figure 6 and Figure 7, the interference test and sensitivity test were both conducted in PBS. Why? It is better to make them consistent.
16. Please rearrange the voltages at the bottom-right of Figure 6 from 0.35 --> 0.40 --> 0.45 V.
17. The sensitivity should be mentioned both in Figure 7 and in the test.
18. Why there are two linear regions in Figure 7? It is necessary to explain this.
19. A table for comparisons of the Au-Pt electrodes should be provided.
20. Some related papers are recommended: (1) Talanta 212 (2020) 120780, (2) Sensors and Actuators B: Chemical 319 (2020) 128279, and (3) Journal of Electroanalytical Chemistry 865 (2020) 114147.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The presented manuscript describes a rather interesting new method to create a gold-based porous Pt electrode for the detection of glucose in artificial and real blood samples. The article contains 1 scheme, 8 figures, and 1 table. The editing is suitable, grammatical errors and misspellings can be read in some sentences. Before the acceptance of the work for publication, I have some comments and questions.

1. In line 120: What does the ‘AuE’ mean? Is it a typo or abbreviation? If it is a mark, please introduce it.
2. In my opinion, the QCM measurement should be carried out to define the total mass of Pt on the Au surface after the synthesis.
3. To complete the SEM measurements, I recommend that you should take a side view to determine the thickness of the Pt layer on the electrode surface. For this purpose, the AFM measurement will be also suitable by analysis of the surface roughness.
4. The XPS analysis is quite poor. I think that the deconvolution of the Pt spectrum is necessary. Moreover, a deeper investigation of the ‘S’ atom binding energies is also required to improve the assumed Pt-S charge transfer.
5. in line 203/204: The glucose is enumerated twice. Please correct it.
6. I cannot read any information about the limit of detection (LOD). The application of any sensor techniques can be accepted in only those cases if two important parameters are defined. The first parameter is the dynamic range (which was appropriately introduced in the manuscript). The second parameter is the limit of detection (LOD) or the limit of quantification (LOQ). Without this parameter, the article cannot be published. For this purpose, I recommend the following article, which contains a freely applicable spreadsheet to calculate the LOD value in the case of sensor measurement.

Loock, H.-P.P.; Wentzell, P.D. Detection limits of chemical sensors: Applications and misapplications. Sensors Actuators, B Chem. 2012, 173, 157–163, doi:10.1016/j.snb.2012.06.071.

After the suggested minor revision, I suggest publishing this nice work in the Catalysts.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Some of the problems have been solved; however, there still remains some. Please refer to the following bullets.

 

1. Line92-line94 says: “The peaks in the anodic scan correspond to different forms of oxide species on the gold surface and the single reduction peak in the cathodic scan is due to removal of the oxide layer when reversing the scan direction.”--> However, if different forms of oxide species on the gold surface were formed during the anodic scan, then it should be reduced back to metallic Au by following the same path. The peaks in anodic and in cathodic are not consistent.
2. It is necessary to mention the potential is based on what reference electrode in Table 1.
3. Some related papers (Au-based and Pt-based) are recommended: (1) Talanta 212 (2020) 120780, (2) Sensors and Actuators B: Chemical 319 (2020) 128279, and (3) Journal of Electroanalytical Chemistry 865 (2020) 114147. Besides, some references are too old to be used. Articles within this decade are recommended.
4. Line236-line237 says: “The calibration curve (inset) displays two distinct regions of linearity. This is not uncommon in non-enzymatic glucose sensors as previously reported (39,40).” --> Reviewer considers that the description should be corrected to “…This is not common……” instead of “…This is not uncommon……”
5. For verifying the sensitivity, please also provide the real surface area, which was also measured in this study.
6. Please define what is the abbreviation of LOD. It only appeared in Table 1 all of a sudden and is not defined anywhere.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

The manuscript has been revised.