Effect of Plasma Treatment on Self-Cleaning Features of Acrylic Paint/TiO₂-Coated Surfaces for Environmental Pollutant Removal

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Accept

Comments on the Quality of English Language

Dear Editor,

Thank you for allowing me to review this manuscript. My suggestion is to accept it.

 

Author Response

Reviewer 1:

Dear Editor, Thank you for allowing me to review this manuscript. My suggestion is to accept it.

Reply: The authors thank the reviewer for positive feedback on publishing the manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

 

The current manuscript presents plasma-treated self-cleaning TiO₂ surfaces: characterization and environmental applications. However, the following significant improvements are necessary:

 

1.Refine the abstract to highlight only the most pivotal results.

2.The introduction is brief and lacks clarity; it requires more comprehensive explanations, such as the rationale behind the chosen component ratios, supported by the literature. Moreover, the reasoning for selecting the materials needs to be strengthened, considering the evolving properties of the composite during its formation.

3.Indept illustration is necessary of how each element contributes to electrochemical performance, How?

4.. Emphasize the innovation of your work in the introduction.

5.Include a detailed list of materials, specifying their purity.

6.Enhance the quality of the figures, include ruler and graph pixels.

7. The authors have not sufficiently discussed background studies, advantages or disadvantages of previous studies, or the hypothesis of this study.

8. All abbreviations of names should be stated in advance when they appear at the first time.eg. SEM, EDS etc.

9.The title of the paper needs revision. Please specify environmental applications.

The abstract needs the following corrections:

10. The Results and Discussion section contains many sentences more suitable for the Experimental sections.

11. Line 554:”The increase in 𝑍_{𝑟𝑒𝑎𝑙} after plasma treatment was attributed to oxygen vacancies in TiO₂, lowering conductivity” . How to prove oxygen vacancy in TiO₂, please explain.

12. The whole analysis process is too tedious, please be concise.

13. The keywords of the paper need revision.

Comments on the Quality of English Language

The language should be carefully polished.

Author Response

Dear Reviewer 2,

The authors thank the reviewer for constructive comments and recommendations. We have taken the comments on board to improve and clarify the Manuscript. We are providing the .docx file with a detailed point-by-point response to all comments.

The reviewer comments are typed in black. The responses to reviewers are tagged blue. The changes in the text of the Manuscript are typed in red.

Kind regards,
Stevan Armaković

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper investigates the effect of plasma treatment on the self-cleaning activity of acrylic paint/TiO2 surface. The doping amount with 0.5 and 2.0 mg/cm3 TiO2 nanoparticles are prepared. Characterization data are compared for the untreated and plasma-treated samples to analyze the structural and performance evolution after the plasma treatment.

However, there are many ambiguous issues in the manuscript.

 

“The size of the incorporated TiO2 nanoparticles was around 10 μm.” However, it is not easy to distinguish the TIO2 nanoparticles from the SEM images shown in Fig. 2. In Fig. 1a, it is hard to estimate the size of TiO2 nanoparticles.

 

In Table 1, it is strange that O and Ti are also detected in the sample of “Acrylic paint”, which should be the pure acrylic paint. Also, why does the TiO2 phase appear in Fig. 4a for the sample of “Acrylic paint”? The manuscript should clearly introduce its samples before the discussion of experimental data.

 

The self-cleaning experiments in Fig. 14 display the photographs after irradiation. It is not easy to evaluate the activity. It is suggested to present the data of quantitative analysis.

 

 

Author Response

Dear Reviewer 3,

The authors thank the reviewer for constructive comments and recommendations. We have taken the comments on board to improve and clarify the Manuscript. We are providing the .docx file with a detailed point-by-point response to all comments.

The reviewer comments are typed in black. The responses to reviewers are tagged blue. The changes in the text of the Manuscript are typed in red.

Kind regards,
Stevan Armaković

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This work is devoted to the investigation of self-cleaning TiO₂ surfaces treated with plasma. The authors obtained interesting results but based on the presented data it is difficult to understand the reason and assess the degree of increase in the self-cleaning effect of the sample surface after plasma treatment.

Below are comments to the article.

 1.    Line 61. TiO₂ can exist in not two, but three crystalline forms: rutile, anatase and brookite.

2.    Line 110. The description of Fig. 1c and the caption to it do not match in meaning.

3.    Line 115. Particles of 10 microns in size cannot be called nanoparticles. Nanoparticles are no larger than 100 nm. Section 3.1 states that the particle size of titanium dioxide is 20 nm. Why did they increase in size significantly?

4.    Figs. 1, 2. At this magnification, it is impossible to distinguish any particles or structural changes on the surface. Everything is the same.

5.    Fig. 5, 6. It is necessary to provide numerical values ​​of contact angles.

6.    Line 473, abstract: What functional groups are we talking about?

7.     A photodegradation mechanism needs to be added.

8.    There are contradictions in the text. On the one hand, the authors report that plasma treatment has a positive effect on the self-cleaning properties of acrylic paint/TiO₂ surfaces, which is due to improved surface wettability. On the other hand, the authors claim that plasma treatment increases the hydrophobicity of the coatings.

9 9. Table 1. Why does the calcium content on the surface increase after introducing titanium dioxide particles into acrylic paint? How can we explain the decrease in the amount of titanium after plasma treatment of the samples?

Author Response

Dear Reviewer 4,

The authors thank the reviewer for constructive comments and recommendations. We have taken the comments on board to improve and clarify the Manuscript. We are providing the .docx file with a detailed point-by-point response to all comments.

The reviewer comments are typed in black. The responses to reviewers are tagged blue. The changes in the text of the Manuscript are typed in red.

Kind regards,
Stevan Armaković

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

The manuscript by Bilic et al deals with a very practical investigation about self-cleaning properties of TiO₂ within acrylic paint mixtures. In particular it is shown that plasma treated materials generally exhibit enhanced performance with different efficiency as a function of the TiO₂ loading employed in the mixture. Samples are characterized by SEM (and EDX) and Raman spectroscopy as well as very exhaustively by impedance spectroscopy and determination of contact angle following exposure of the samples to puddle sediment and car oil employed to evaluate self-cleaning performance of the samples. Main conclusions are related to higher self-cleaning activity of plasma treated acrylic paint/TiO₂-coated aluminum foil, with TiO₂ concentration of 0.5 mg/cm³ attributed to the facts that “plasma treatment reduced agglomeration and increased active sites” as well as (induced) “morphological changes and TiO₂ incorporation into the matrix”. Such conclusions are mainly based on SEM images with relatively low spatial resolution and in which on the basis of some morphological differences  it appears difficult to extract detailed conclusions on specific changes at the nano level which can be most relevant to explain the performance differences observed (based on visual detection). In fact, no difference in the Raman spectra is reported further than differences in the background level as a consequence of the plasma treatment and from which detailed structural details are difficult to be inferred. The use of TEM for exploring such differences in more detailed is asked in such senses. The other characterization technique employed (impedance spectroscopy) allow to detect differences but this is a technique focussed to the electrical properties of the materials and from which structural details are only indirectly inferred. In page 3 (lines 116-119): “From Figure 2b, it can be seen that the TiO2 nanoparticles are smaller than 10 μm and that the plasma treatment affected surface morphology by increasing the contact surface, which can lead to increased photocatalytic activity and thus to the improvement of self-cleaning properties of synthesized acrylic paint/TiO2 surfaces.”, knowledge of the specific surface area of before and after plasma treatment would be required to confirm that. The SEM images show in any case limited spatial resolution. In page 6 (lines 176-179) The intensity of anatase modes increases with the higher amount of TiO2 powder added to acrylic paint, but also somewhat varies within the same acrylic sample, pointing out that the TiO2 powder is not quite uniformly dispersed in the paint. Can authors include any more specific analysis in such sense (even if in supporting information; i.e. if different zones are available include spectra showing the mentioned dispersion of intensity in comparative terms). In page 19 (lines 469-471) “With the use of 2.0 mg/cm3 TiO2 content, more nanoparticles are dispersed on the surface of acrylic paint/TiO2 coatings (Figure 2), and the irradiation probably could not get evenly dispersed onto the TiO2 nanoparticles”, this is expected to be specifically characterized (by TEM, for instance). No evidence of mentioned presence of vacancies in most active sample is given either, only indirect ones.  

Author Response

Dear Reviewer 5,

The authors thank the reviewer for constructive comments and recommendations. We have taken the comments on board to improve and clarify the Manuscript. We are providing the .docx file with a detailed point-by-point response to all comments.

The reviewer comments are typed in black. The responses to reviewers are tagged blue. The changes in the text of the Manuscript are typed in red.

Kind regards,
Stevan Armaković

Author Response File: Author Response.pdf

Reviewer 6 Report

Comments and Suggestions for Authors

Review

 

Manuscript ID: catalysts-3235056

 

Title: Plasma-treated self-cleaning TiO2 surfaces: characterization and environmental applications

Authors: Andrijana Bilić, Sanja J. Armaković, Mirjana V. Šiljegović, Milica Kisić, Maja Šćepanović, Mirjana Grujić-Brojčin, Nataša Simić, Lazar Gavanski, Stevan Armaković, Maria M. Savanović

 

 

 

The presented manuscript studies "coating aluminum foil with an acrylic paint mixture containing nanoparticles of different mass compositions and subsequent plasma treatment using a continuous plasma arc". The work in principle promised to be interesting, but it is unlikely that with such a formulation it corresponds to the subject of the journal Catalysts. At the same time, the reviewer is not against its publication in this or another journal after working on the text and eliminating the comments given below.

 

Comments

 

1. It seems to me that the composition of puddle sediment varies depending on the location on the map and the time of year. For this reason, some of the results obtained by the authors of the manuscript under review can be classified as non-reproducible.

 

2. Line 109 "tunnel morphology of Al foil". I did not see the tunnel morphology of Al foil in Figure 1. A tunnel is a horizontal or inclined underground structure, one of whose dimensions (length) significantly exceeds the other two (width and height).

 

3. Lines 115-116 "The size of the incorporated TiO2 nanoparticles was around 10 μm". Nanoparticles are particles in which at least one of the dimensions is less than 100 nm. By the way, in section 3.1 it is written "TiO2 particle size 20 nm". At what stage did the increase in size occur?

 

4. Lines 116-118 «From Figure 2b, it can be seen that the TiO2 nanoparticles are smaller than 10 μm and that the plasma treatment affected surface morphology by increasing the contact surface». From the presented figure, I do not see that after «plasma treatment» there was a decrease in the size of «TiO2 nanoparticles». The authors should either refuse these words or provide such SEM images from which this will be clear. By the way, microscopy is a quantitative method, so it is necessary to say how much the sizes of «TiO2 nanoparticles» decreased.

 

5. Lines 120-126. Very strange comments on the data in Table 1. It is clear that plasma treatment leads to a decrease in the titanium concentration in the analyzed paint layer. How is this related to the statement about "increasing the contact surface?" Further, in the Acrylic paint/0.5 TiO2 sample, the aluminum content is 0.77 wt. %, and in the Acrylic paint/0.5 TiO2 – plasma sample, it is 0.00 wt. %. Based on these data, we can conclude that the thickness of the paint layer after "plasma treatment" increased, right? Finally, there is no explanation why the paint was taken as a base, which, according to EDC, contains more than 10 wt. % titanium dioxide. What effect did the authors hope to achieve by adding another 0.5 mg/dm³ titanium dioxide to it? How much will it be in weight percent? – to make it easier to compare. A very strange formulation of the work.

 

6. Lines 146-149 “However, low intensity modes (shown enlarged in the inset) which can be ascribed to brookite ~ 218 (B1g), (A1g), 288 (B3g), 322 (B1g), and 366 cm‒1 (B2g), point to the presence of the very small amount of highly disordered brookite phase in TiO2 powder [17]”. I propose to remove this phrase from the text, because a) the inset in Figure 3 is unconvincing and b) these data are not discussed further.

 

7. Lines 165 "1732 (C‒O stretching)". More precisely 1732 (C=O stretching)

 

8. Lines 194-195 "Therefore, subtle changes on the very surface of the sample potentially caused by plasma may not be accessed by Raman scattering". Is this the main conclusion that the authors made based on the study of the Raman spectra? Was not it known in advance that the Raman method is not a surface method, like, for example, XPS?

 

9. Lines 209-211 "Surfaces that exhibit both a high contact angle and a sliding angle below 10° are considered to have self-cleaning properties". Why is this phrase written? There is not a word about "sliding angle" in the manuscript. Moreover, there are no numerical data on the contact angle either. There are no indications of the method by which the contact angle was determined. In the simplest case (sessile drop), the drop contour should be analyzed taking into account the physical properties of the liquid and the curved surface of the interface (for example, using the Young-Laplace method).

 

10. Let us now turn to the most important thing – experiments on the so-called self-cleaning. Lines 543 “the source positioned 50 mm from the tiles”. I have not found any information anywhere about how much the sample temperature increased with such an experimental geometry.

 

11. Lines 432-434 "However, car oil fading within 3 h (10 and 20 μL, respectively) was evident on untreated surfaces, attributed to the amount of TiO2 within the commercial acrylic paint (Figure 1, Table 1)". The authors honestly admit that 10 wt.% titanium dioxide within the commercial acrylic paint works!

 

12. Lines 446-448 «Specifically, Raman's analysis pointed out the strongest impact of plasma treatment on the acrylic paint/0.5 TiO2 sample seen through the highest background level as the consequence of the changes in surface area induced by plasma treatment». Here the authors associate «the highest background level» with the increased surface area. Although there is no basis for this (there are no data on the specific surface area). At the same time, it is well known that the background can be associated with luminescence. The luminescence intensity is usually greater than the intensity of the combined scattered radiation. There may be several reasons for the occurrence of luminescence. For example, accidental contamination of the sample at the analysis site or high laser power. Why do the authors not consider these reasons?

 

 

13. Figure 14. In my opinion, the most effective compositions for a small drop of machine oil are acrylic paint and acrylic paint/2.0 TiO2, which have not been treated with plasma. There are practically no traces of oil visible on the surface of these samples after 3 hours of irradiation.

 

 

14. Lines 548-550 "Achieving sustainable urban development requires maintaining clean urban environments amidst growing populations and industrial activity". I suggest removing this phrase from section 4. Conclusions. It has no relation to the work done.

 

Author Response

Dear Reviewer 6,

The authors thank the reviewer for constructive comments and recommendations. We have taken the comments on board to improve and clarify the Manuscript. We are providing the .docx file with a detailed point-by-point response to all comments.

The reviewer comments are typed in black. The responses to reviewers are tagged blue. The changes in the text of the Manuscript are typed in red.

Kind regards,
Stevan Armaković

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

In view of the revision provided by authors, this manuscript can be accepted.

Author Response

Dear Reviewer,

Thank you very much for your positive feedback and for recommending our manuscript to be accepted for publication in this fine journal.

All the best

 

Reviewer 3 Report

Comments and Suggestions for Authors

In the revised version, the manuscript has been revised according to the comments. 

Author Response

Dear Reviewer,

Thank you very much for your positive feedback and for recommending our manuscript to be accepted for publication in this fine journal.

All the best

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have significantly improved the manuscript and I now recommend it for publication.

Author Response

Dear Reviewer,

Thank you very much for your positive feedback and for recommending our manuscript to be accepted for publication in this fine journal.

All the best

Reviewer 6 Report

Comments and Suggestions for Authors

Review No. 2

 

Manuscript ID: catalysts-3235056

 

Title: Effect of plasma treatment on self-cleaning features of acrylic paint/TiO₂ coated surfaces for environmental pollutant removal

Authors:  Andrijana Bilić, Sanja J. Armaković, Mirjana Šiljegović, Milica Kisić, Maja Šćepanović, Mirjana Grujić-Brojčin, Nataša Simić, Lazar Gavanski, Stevan Armaković *, Maria M. Savanović

 

 

The authors agreed with all my comments and gave generally informative responses to them. If the editors agree with their answers and corrections, then I will also not object to the publication of the manuscript.

 

 

Author Response

Dear Reviewer,

Thank you very much for your positive feedback and for recommending our manuscript to be accepted for publication in this fine journal.

All the best