Self-Cleaning Coatings for the Protection of Cementitious Materials: The Effect of Carbon Dot Content on the Enhancement of Catalytic Activity of TiO₂

Round 1

Reviewer 1 Report

The manuscript “Self-Cleaning Coatings for the Protection of Cementitious Ma- 2 terials: The Effect of Carbon Dot Content into the Enhancement 3 of Catalytic Activity of TiO2” introduced a new durable C-dots/TiO2 photocatalysts that can operate under outdoor weather conditions and be used for building protection against pollution. The study is interesting. Here below is some advice:

-Introduction-

A lot of space is used to present your previous work, you should also refer to other people’s work and give a comprehensive review of this field.

The novelty of the research should be pointed early rather than one single sentence of the last paragraph.

 

-Materials and Methods-

1. From section 2.4 to 2.7: the title is too long.
2. in section 2.7, is introduced to quantify the self-cleaning performance. However, this index is not used in the following section. Why?

 

-Results and discussion-

1. some figures are not clear: Figure 6, Figure 11. Please revise them.
2. section 3.3 “To study the self-cleaning properties of the specimens with the different protective films, two drops (around 0.025 mL each) of methylene blue (MB) were released on each coating and its degradation was evaluated by comparing the color difference of the stained surface with the color of the surface before application” please add some pictures to illustrate it clearer.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The work presents an interesting study of the photocatalytic activity of the C-dot/TiO2  photocatalysts on the solution and over concrete, the results are supported by appropriate techniques. The work is original and interesting. However, there are some observations that can improve the scientific quality of the work. Therefore, my recommendation is for major revision.

1. There are some mistakes typos in the introduction of the manuscript.
2. Revise all the data in the tables.
3. In the introduction section, the following references may help in the PDMS/SiO2/TiO2 composites: Rosales, A.; Maury-Ramírez, A.; Gutiérrez, R.M.-D.; Guzmán, C.; Esquivel, K. SiO₂@TiO₂ Coating: Synthesis, Physical Characterization and Photocatalytic Evaluation. Coatings 2018, 8, 120. https://doi.org/10.3390/coatings8040120 Rosales, A.; Esquivel, K. SiO₂@TiO₂ Composite Synthesis and Its Hydrophobic Applications: A Review. Catalysts 2020, 10, 171. https://doi.org/10.3390/catal10020171 A. Rosales, L. Ortiz-Frade, Iliana E. Medina-Ramirez, Luis A. Godínez, K. Esquivel,Self-cleaning of SiO2-TiO2 coating: Effect of sonochemical synthetic parameters on the morphological, mechanical, and photocatalytic properties of the films,
   Ultrasonics Sonochemistry,Volume 73, 2021, 105483, ISSN 1350-4177,
   https://doi.org/10.1016/j.ultsonch.2021.105483 
4. Table S2 is not present in the supplementary as mentioned in line 198.
5. Fig 7 does not exist in the MS, was mentioned in line 253.
6. In fig 4, the crystal planes are discussed, which are attributed to the anatase phase. How can you assure there are planes over the micrographic on a scale of 20 nm and correlated with the anatase phase? Proper analysis in HRTEM should be provided or reframe the ideas explained and discuss by adding proper reference
7. In the XRD analysis of the photocatalyst, explain the method to determinate the size of crystallite, however, the values are never shown or discussed. Employ a method with major precision.
8. The FTIR spectra are not clear, realize zoom in the region of 1600 to 1000 cm-1 helps to observe the shifts on the bands.

Author Response

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Reviewer 3 Report

The following issues must be addressed:

1. Introduction part should contains more relevant references about TiO2 photocatalytic applications (DOI: 10.1016/j.apsusc.2011.12.110; DOI: 10.1016/j.mssp.2022.106610; DOI: 10.1016/j.inoche.2022.109340);
2. The authors should explain why MO was chosen for photocatalytic experiments.
3. Light irradiance (mW/cm2) used for photocatalytic experiments should be provided.
4. Figure 6 resolutions should be improved.
5. Subchapter 3.1 resumes to data presentation but no discussions. The authors should compare and discuss the results.
6. TOC analysis is required in order to be sure that the MO was partially decomposed or mineralized.
7. Figure 11 resolution should be improved.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have made a good effort to address the comments. The reviewer is happy to recommend it for publication.

Author Response

We thank you for improving our manuscript with your observations, comments and suggestions. Some additional revisions were submitted, as a reply to the comments of Reviewer 2.

Reviewer 2 Report

According to the previous reviewers’ answers and by a second look at the new version of the MS, I have these observations:

• The observation “In fig 4, the crystal planes are discussed, which are attributed to the anatase phase. How can you assure there are planes over the micrographic on a scale of 20 nm and correlated with the anatase phase? Proper analysis in HRTEM should be provided or reframe the ideas explained and discussed by adding proper references” done in the previous review is still not adequately answered, and the authors “justify” by words the explanation but not with HRTEM images or with some references to support the fact that they are observing anatase phase planes. And instead of taking advantage of the XRD information, the decision to avoid showing an estimation of the crystallite size. Also, they mentioned that by relating the XRD information and the TEM images is possible to “corroborate” the anatase phase planes. They are right; by XRD, it is possible to say that, but again not with the TEM images shown, because as it is well known, the HRTEM done by contrast is the only way to determine the material phase planes and relate it with XRD.
• The observation in the previous review, “In the XRD analysis of the photocatalyst, explain the method to determinate the size of crystallite. However, the values are never shown or discussed. Employ a method with major precision.” It wasn’t answered and just removed instead of having a better results discussion to enrich the work. This should not be done, or if the authors decide to do it, they must give a better justification.
• Figures 8a and 9, please explain why the TC25 and TC50 samples stopped at 80 min and 50 min, respectively.
• Line 413, the frame of Table 1, seems duplicated.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript can be published in the present form.

Author Response

We thank you for improving our manuscript with your observations, comments and suggestions. Some additional revisions were submitted, as a reply to the comments of Reviewer 2.