Evaluation of the Performance and Durability of Self-Cleaning Treatments Based on TiO2 Nanoparticles Applied to Cement-Based Renders and Boards
Round 1
Reviewer 1 Report
Referee report: “Evaluation of the performance and durability of self-cleaning TiO2 treatments applied to cement-based renders and boards”
This is a very interesting and quite important research communication that probably can be recommended for publication, but only after clarifying and detailing some parts of the text.
1. In the introduction, we would like to see how important the size of nanoparticles and their size distribution are. What factors in a compartment improve/enhance the functionality of the coatings. See for example:
Dorosheva, I.B., et al. Synthesis and Physicochemical Properties of Nanostructured TiO2 with Enhanced Photocatalytic Activity. Inorg Mater 57, 503–510 (2021). https://doi.org/10.1134/S0020168521050022
2. Can impurities improve functionality of based on TiO2 nanoparticles photocatalytic coatings.
Serga, V., et al (2021). Study of phase composition, photocatalytic activity, and photoluminescence of TiO2 with Eu additive produced by the extraction-pyrolytic method. Journal of materials research and technology, 13, 2350-2360.
Cerrato, E., Gaggero, E., Calza, P., & Paganini, M. C. (2022). The role of Cerium, Europium and Erbium doped TiO2 photocatalysts in water treatment: A mini-review. Chemical Engineering Journal Advances, 100268.
3. It seems that it would be useful during the test of discoloration of the methylene blue stain to also carry out 2-dimensional mapping using Raman/photoluminescence methods.
In general, the manuscript is interesting and can be recommended for publication after constructive reflection on the above comments.
Author Response
Response to reviewer #1 (as in the attached word file)
This is a very interesting and quite important research communication that probably can be recommended for publication, but only after clarifying and detailing some parts of the text.
- In the introduction, we would like to see how important the size of nanoparticles and their size distribution are. What factors in a compartment improve/enhance the functionality of the coatings. See for example:
Dorosheva, I.B., et al. Synthesis and Physicochemical Properties of Nanostructured TiO2 with Enhanced Photocatalytic Activity. Inorg Mater 57, 503–510 (2021). https://doi.org/10.1134/S0020168521050022
Response:
We thank for the suggestion. We added a reference to the role of nanoparticle size and other parameters in the Introduction.
- Can impurities improve functionality of based on TiO2 nanoparticles photocatalytic coatings.
Serga, V., et al (2021). Study of phase composition, photocatalytic activity, and photoluminescence of TiO2 with Eu additive produced by the extraction-pyrolytic method. Journal of materials research and technology, 13, 2350-2360.
Cerrato, E., Gaggero, E., Calza, P., & Paganini, M. C. (2022). The role of Cerium, Europium and Erbium doped TiO2 photocatalysts in water treatment: A mini-review. Chemical Engineering Journal Advances, 100268.
Response:
We thank for the suggestion. We added some reference to the possible influence of doping in the Introduction.
- It seems that it would be useful during the test of discoloration of the methylene blue stain to also carry out 2-dimensional mapping using Raman/photoluminescence methods.
Response:
We appreciate the suggestion by the Reviewer, but unfortunately we have not the equipment to perform such mapping. We will surely consider this option for further studies, maybe by looking for suitable partners able to help us with this analysis.
In general, the manuscript is interesting and can be recommended for publication after constructive reflection on the above comments.
Reviewer 2 Report
Although the paper falls within the scope and objectives of Coatings Journal, it cannot be recommended for publication as it stands. The work must undergo a major review before further evaluation.
The main drawbacks are the following:
- The word nanoparticles should be included in the title since it is one of the major points that influence the work.
- I think that the keywords do not correspond to the work that is exposed.
- In the introduction name anatase. But they should talk about all the crystalline forms that TiO2 presents, since each one plays an important role and each one favors some properties or others. This is important because, depending on the application being searched for, one or the other will be used.
- They must define all the initials that they put. In the case of VOCs, they must define the full name.
- I find it very interesting that you comment that TiO2 nanoparticles present a serious problem in human health and that there are problems in the legislation. There is a paper that deals with TiO2 NPs in food that comments on it (10.1016/j.aca.2018.10.067). In addition, it is important that they comment on some examples in other sectors such as food that comment on the work that I have suggested. This is important because they are direct routes that reach the human being and that reach the human body directly.
- Why have you selected those 3 substrates in particular?
- Be careful with the data format and units. Sometimes they put the number and the unit with a space, other times with a space, etc. THEY MUST FOLLOW THE FORMAT THROUGHOUT THE ENTIRE MANUSCRIPT. PLEASE BE VERY CAREFUL.
- Figure 1 is very concise. They can put more thing and give more information.
- In the methods part you can put a figure with a general outline of the entire process carried out in this work.
- In line 112 and 154 (for example) they must put the name of TiO2 correctly. The 2 as a subscript.
- The authors say they have done the studies with pure anatase. Because? Why not with rutile, or a mixture of both? Justify it.
- In line 125, what does "room conditions" mean?
- Sometimes it says Fig. and other times Figure. Please, always respect the same format throughout the manuscript. And the same goes for tables.
- Sometimes they put nano-TiO2 and other times nano-TiO2. Respect the format.
- Why have you selected only 5 points?
- Is the method used reproducible? Justify with data.
- The letters in figure 4 and the images are not clear. Change them. - If you put colors in the EDX image, it would be easier to understand.
- SEM images look bad. Modify them. The resolution is also very bad.
- In the part made with UV, I recommend that you make a scheme of what may be happening.
I don't think English is very bad. Maybe a short review. But not much.
Author Response
Response to reviewer #2 (as in the attached word file)
Although the paper falls within the scope and objectives of Coatings Journal, it cannot be recommended for publication as it stands. The work must undergo a major review before further evaluation.
The main drawbacks are the following:
- The word nanoparticles should be included in the title since it is one of the major points that influence the work.
Response:
Done. We have included the term nanoparticles, whom the study is referred to.
- I think that the keywords do not correspond to the work that is exposed.
Response:
Amended. We modified the keywords to make them better reflect the subject of the study.
- In the introduction name anatase. But they should talk about all the crystalline forms that TiO2 presents, since each one plays an important role and each one favors some properties or others. This is important because, depending on the application being searched for, one or the other will be used.
Response:
Amended. This aspect was added in the Introduction, with the relevant references.
- They must define all the initials that they put. In the case of VOCs, they must define the full name.
Response:
Amended.
- I find it very interesting that you comment that TiO2 nanoparticles present a serious problem in human health and that there are problems in the legislation. There is a paper that deals with TiO2 NPs in food that comments on it (10.1016/j.aca.2018.10.067). In addition, it is important that they comment on some examples in other sectors such as food that comment on the work that I have suggested. This is important because they are direct routes that reach the human being and that reach the human body directly.
Response:
Thanks for the suggestion. We added the mentioned study to emphasise the lack of knowledge on the hazards of TiO2 for human health and environment, although we think that an exhaustive discussion of these hazards in a variety of sectors goes beyond the scope of the present paper.
- Why have you selected those 3 substrates in particular?
Response:
Done. We have explained the reasons for the selection in section “2.1 Substrates”.
- Be careful with the data format and units. Sometimes they put the number and the unit with a space, other times with a space, etc. THEY MUST FOLLOW THE FORMAT THROUGHOUT THE ENTIRE MANUSCRIPT. PLEASE BE VERY CAREFUL.
Response:
Thanks for the hint. We have carefully checked the manuscript and amended where necessary.
- Figure 1 is very concise. They can put more thing and give more information.
Response:
Done. We added more information about the application procedure in the text.
- In the methods part you can put a figure with a general outline of the entire process carried out in this work.
Response:
Done. We have modified Figure 2 and added the new Figure 3, providing the suggested outline.
- In line 112 and 154 (for example) they must put the name of TiO2 correctly. The 2 as a subscript.
Response:
Amended. Thanks for noticing these typos.
- The authors say they have done the studies with pure anatase. Because? Why not with rutile, or a mixture of both? Justify it.
Response:
The study was carried out using a commercial product constituted of anatase, as it was considered representative of a number of products available in the Italian market for the surface treatment of finishing materials in residential and commercial buildings, as well as in heritage buildings. This clarification was added in the text.
- In line 125, what does "room conditions" mean?
Response:
The term “room conditions” was substituted with “laboratory conditions (temperature 20±2°C, relative humidity 55±5%)”.
- Sometimes it says Fig. and other times Figure. Please, always respect the same format throughout the manuscript. And the same goes for tables.
Response:
Amended. Thanks for noticing this.
- Sometimes they put nano-TiO2 and other times nano-TiO2. Respect the format.
Response:
We amended all the inconsistencies.
- Why have you selected only 5 points?
Response:
Given the natural slight heterogeneity of building materials, we decided to use a single sample (slab) to test all the conditions under investigation. This led to a limited number of points for methylene blue discolouration test, but to a significant benefit in terms of results’ comparability.
We better explained this in the text.
- Is the method used reproducible? Justify with data.
Response:
The results found in this study are consistent and allowed to make some interesting observations that may help in better understanding some factors affecting the effectiveness and durability of the investigated coatings. However, further studies are running to specifically investigate these factors.
The borders of this study were recalled in the Conclusions, to explain this aspect.
- The letters in figure 4 and the images are not clear. Change them. - If you put colors in the EDX image, it would be easier to understand.
Response:
Done. We improved the clarity of Figure 4 (now Figure 5). Unfortunately, it is no more possible to put colors in the maps, which are in any case all referred to Ti.
- SEM images look bad. Modify them. The resolution is also very bad.
Response:
We improved the quality of the figure at the best of our possibilities.
- In the part made with UV, I recommend that you make a scheme of what may be happening.
Response:
We tried to make the description and comment of the results more schematic.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The article evaluates the performance and durability of self-cleaning TiO2 treatments applied to cement-based renders and boards. The study investigates the behavior of a nanodispersion of titania nanoparticles applied to cement-based substrates and its photocatalytic activity. The results suggest that the nature of the substrate plays a key role in the performance of the coating and that weathering has a significant impact too. The study evaluated the self-cleaning performance of TiO2-based coatings on different substrates using methylene blue degradation test and contact angle measurements. The results showed that the porosity, wettability, and rate of capillary absorption of the substrate play a significant role in the test. Further studies are necessary to elucidate the pros and cons of these coatings in real substrates and conditions. The article is very well written and I recommend it for publication in Coatings, subject to the following corrections. Although the correction I am suggesting in the list of results and discussion may seem major, in my opinion they are minor and the authors should break the text into paragraphs as it is more typical of an academic article (the other style is more like a report).
Line 52. Write the minus symbol of the anion correctly.
Line 58. Remove the space between nano and TiO2, I think it looks better. Same on line 58, 66, etc. The format as in section 2.2. seems more correct to me.
Delete the text between lines 91 and 93 that has not been removed from the format.
The substrates would look better in italics than in quotation marks.
Line 102. Insert a full stop at the end of the sentence.
Line 105: Add a full stop at the end of the sentence. You could also use a ";".
Line 112: Make the 2 a subscript.
Figure 1. Remove the lines and align the literals a), b) and c). Same comment for Figure 2, where the literal c) is incorrectly placed.
Line 125. POner Figure instead of Fig. as the caption of the figure is Figure. Do the same on line 133 and the remaining lines.
Line 137 Index the text.
Line 146. Insert mg l^-1 instead of mg/l, which is no longer used.
Line 154 Place 2 as a subscript. Same on line 160.
Line 168: use Ctrl+Shift+Space so that the units do not jump to the next line and stay together with the number.
Line 205: insert ";" at the end of the sentences (do this throughout the list).
Line 209. Write Table instead of Tab as in the previous cases.
Table 1. Uncertainty is not written between (), remove it. Authors should also indicate whether the coverage factor is k=1 or k=2 in the footer of the table. Leave a space between the table and the text.
Line 248 and Table 2. What is No Ti. I don't know if they missed it (if there are quantitative values). Please clarify.
As with the text starting on line 200, in the case of line 252, the enumeration does not seem advisable to me, the authors should write the text in three paragraphs with one idea each.
Table 2. Write the uncertainty correctly, I do not know if the uncertainty is % or absolute. Please clarify this in Tables 1 and 2. The value of 8.1 would not be well expressed if it were in absolute value because the authors have used 2 significant figures in the rest of the values and not in this case. The same happens with the uncertainties 0.1, 0.7....
Line 295. Write "." at the end of the figure caption.
Author Response
Response to reviewer #3 (as in the attached word file)
The article evaluates the performance and durability of self-cleaning TiO2 treatments applied to cement-based renders and boards. The study investigates the behavior of a nanodispersion of titania nanoparticles applied to cement-based substrates and its photocatalytic activity. The results suggest that the nature of the substrate plays a key role in the performance of the coating and that weathering has a significant impact too. The study evaluated the self-cleaning performance of TiO2-based coatings on different substrates using methylene blue degradation test and contact angle measurements. The results showed that the porosity, wettability, and rate of capillary absorption of the substrate play a significant role in the test. Further studies are necessary to elucidate the pros and cons of these coatings in real substrates and conditions. The article is very well written and I recommend it for publication in Coatings, subject to the following corrections. Although the correction I am suggesting in the list of results and discussion may seem major, in my opinion they are minor and the authors should break the text into paragraphs as it is more typical of an academic article (the other style is more like a report).
Response:
We thank the reviewer for his/her appreciation of our work.
Line 52. Write the minus symbol of the anion correctly.
Response:
Done. We checked all the manuscript.
Line 58. Remove the space between nano and TiO2, I think it looks better. Same on line 58, 66, etc. The format as in section 2.2. seems more correct to me.
Response:
Amended.
Delete the text between lines 91 and 93 that has not been removed from the format.
Response:
Amended. Thanks for noticing the error.
The substrates would look better in italics than in quotation marks.
Response:
Done.
Line 102. Insert a full stop at the end of the sentence.
Response:
Done.
Line 105: Add a full stop at the end of the sentence. You could also use a ";".
Response:
Done.
Line 112: Make the 2 a subscript.
Response:
Done.
Figure 1. Remove the lines and align the literals a), b) and c). Same comment for Figure 2, where the literal c) is incorrectly placed.
Response:
Done.
Line 125. POner Figure instead of Fig. as the caption of the figure is Figure. Do the same on line 133 and the remaining lines.
Response:
Done.
Line 137 Index the text.
Response:
Done.
Line 146. Insert mg l^-1 instead of mg/l, which is no longer used.
Response:
Done.
Line 154 Place 2 as a subscript. Same on line 160.
Response:
Done.
Line 168: use Ctrl+Shift+Space so that the units do not jump to the next line and stay together with the number.
Response:
Done.
Line 205: insert ";" at the end of the sentences (do this throughout the list).
Response:
Done.
Line 209. Write Table instead of Tab as in the previous cases.
Response:
Done.
Table 1. Uncertainty is not written between (), remove it. Authors should also indicate whether the coverage factor is k=1 or k=2 in the footer of the table. Leave a space between the table and the text.
Response:
The values in brackets are the standard deviations of the measured values. We added this clarification in the caption.
Line 248 and Table 2. What is No Ti. I don't know if they missed it (if there are quantitative values). Please clarify.
Response:
Amended. We clarified this in the text.
As with the text starting on line 200, in the case of line 252, the enumeration does not seem advisable to me, the authors should write the text in three paragraphs with one idea each.
Response:
Done.
Table 2. Write the uncertainty correctly, I do not know if the uncertainty is % or absolute. Please clarify this in Tables 1 and 2. The value of 8.1 would not be well expressed if it were in absolute value because the authors have used 2 significant figures in the rest of the values and not in this case. The same happens with the uncertainties 0.1, 0.7....
Response:
Same as above. The values in brackets are the standard deviations of the measured values.
Line 295. Write "." at the end of the figure caption.
Response:
Done.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Changes have been made. Thank you for the corrections.
Authors have made a huge effort in the review proccess. The new version can be published.
