Diamond as Insulation for Conductive Diamond—A Spotted Pattern Design for Miniaturized Disinfection Devices

Round 1

Reviewer 1 Report

The authors of the manuscript proposed a promising electrode design based on layers of boron-doped and undoped carbon material deposited on a niobium wire. Unfortunately, information about the deposition of layers by the hot filament method (pressure of gases, their flow rates, etc.), as well as characterization of the resulting layers (Raman spectroscopy, X-ray diffraction, electrochemical parameters, etc.) is not available in the manuscript. The manuscript also does not discuss the problems of corrosion in such a multilayer structure, which is critical during its operation.

Author Response

Dear Sir or Madam,

thank you for your review and input to our manuscript.

Please find the answers to your review in the attached file.

Best wishes!

Author Response File: Author Response.docx

Reviewer 2 Report

This paper presents an attempt to demonstrate the fabrication of an all-diamond microelectrode prototype and its oxidant production capability. Overall, the concept and methodology discussed is interesting and novel. However, the following suggestions are to be incorporated.

1. The writing style is a bit "jumpy". For example in the abstract the authors begin with the use of BDD in wastewater treatment (lines 13-15) and suddenly jump to medical applications - without mentioning specific medical applications.

The authors are to create a better text flow. In this case in the abstract, the authors are recommended to state in which medical application the application of BDD electrodes to produce strong oxidants would be useful, before continuing on to miniaturization, etc.

2. Materials and methods: Authors have shown cross section of the Nb wire after BDD and UDD coating in Figure 5. How were these cross sections made? The authors are to clarify this in the materials and methods section.

3. Results and discussion:

While the study presents some interesting results, they lack sufficient rigor - in terms of statistics.

a. The authors are recommended to analyze and present the thickness of the UDD and BDD of multiple cross sections (at least three) and provide the average thicknesses with standard deviations.

b. The authors are strongly recommended to add a photograph and a low-res optical micrograph/SEM image of the prototype after the two coating processes.

c. Figure 4. shows the SEM image of the copper particles (with artificial coloring, presumably). The authors are recommended to present EDX images (multiple) and discuss the distribution of copper (and particle sizes).

A similar analysis is recommended after the etching process.

d. It would be useful to also see the EDX data from the cross sections - at the least before Cu deposition, after Cu deposition and after etching.

e. With regard to Figure 5. the authors mention dotted yellow lines "indicate potential pores". However, it is not clear from the images as the layer appears solid. 

f. In general, the authors are to refrain from artificial coloring of the different layers. Instead, please simply mark the areas. In case the authors do stick to the coloring, best to mention this in the image captions explicitly.

g. In  line 198-200, the microstructure of UDD and BDD are described without direct experimental evidence. The authors are to present evidence for "columnar crystals" and "nano-based grown diamond".

h. In Figure 6., it seems the authors have varied the UDD deposition time and compared the results. This is a bit confusing - because the materials and methods section states that this time was fixed at 20 h. The authors are to alter the materials and methods section appropriately. 

i. In terms of discussing the porosity for Figure 6, the authors are to include 5h, 15h, and 20 h and provide some estimates of surface porosity at least from SEM image analysis.

j. Please present the EDX image of Fig. 6(d).

k. For section 3.4., the authors are to provide H2O2 concentrations vs. voltage as well as the current voltage plots and discuss this a bit more.

l. The authors are to explain in more detail how they came to the number "80% of BDD area is electrochemically active." (line 234).

m. Similarly, it is unclear how the authors arrive at the number "approximately 20% of the BDD surface area is directly overgrown with UDD" (lines 275-277). The authors are to provide more (cross section) microscopy evidence as well as calculations to support this and then go on to compare/discuss improvement over Koch et al.'s results.

If not in the main paper, please present the calculations/microscopy evidence in supplementary material.

n. Line 224: the bending test is not well defined. What force was applied. The authors are to either simply include a video if this test was qualitative. Or use more rigorous bending test conditions and present the results. 

As mentioned earlier, the writing style is a bit disconnected. One example  about the abstract is mentioned. 

There are also slightly unconventional use of language sporadically. For example, "nano-based grown diamond" (L199), by which I presume the authors intend to convey the nanocrystalline nature of the diamond.

The authors are recommended to check the manuscript for better continuity and flow.

Author Response

Dear Sir or Madam,

thank you for your detailed review and suggestions.

Please see the answers in the attached file.

Best wishes!

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I am not entirely satisfied with the response of the authors of the manuscript. The text of the manuscript states several dozen times that diamond films were deposited on the surface of the wire, but this fact is confirmed indirectly only by the morphology of undoped carbon layers. Raman spectroscopy is a routine technique that makes it possible to determine not only the presence of a diamond layer, but also the degree of its structural perfection, the fraction of non-diamond phase inclusions, mechanical stresses, and the boron doping level. All these factors significantly affect the parameters of diamond electrodes, including their performance and durability. The degree of reliability of the obtained results is determined by the possibility of reproducing them. I believe that confirmation of the fact of diamond layers deposition, including diamond doped with boron, is a necessary requirement for the publication of the manuscript.

Author Response

Please find our answer in the attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors have made largely changes to the manuscript in line with the review recommendations and I recommend the publication of the article.

 There are still some issues with grammatical/language errors here and there. The authors are recommended to proof read using professional services.  

 There are still some issues with grammatical/language errors here and there. The authors are recommended to proof read using professional services.  

Author Response

Please find our answer in the attached file.

Author Response File: Author Response.docx

Round 3

Reviewer 1 Report

I am completely satisfied with the responses to the comments and the changes made to the text of the manuscript and supplementary materials. The authors of the manuscript have done a good job and the text has improved significantly. I recommend this paper for publication in journal C.