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Article
Peer-Review Record

Low Temperature Deposition of TiO2 Thin Films through Atmospheric Pressure Plasma Jet Processing

Catalysts 2021, 11(1), 91; https://doi.org/10.3390/catal11010091
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Catalysts 2021, 11(1), 91; https://doi.org/10.3390/catal11010091
Received: 13 December 2020 / Revised: 5 January 2021 / Accepted: 8 January 2021 / Published: 11 January 2021
(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Akira Fujishima)

Round 1

Reviewer 1 Report

Titanium dioxide is one of the most studied material recently due to its many interesting properties. However, this subject is still "open book" and investigations related to immobilization of TiO2 on different substrates is extremely interesting from application point of view.
The authors in the article presented the results of study on the preparation of TiO2 coatings on glass and silicon substrates by atmospheric pressure plasma jet (APPJ) technique. The effect of gases like He, Ar, water vapor and gas flow rate on the structural, morphological, optical properties of TiO2 thin films were also studied. The authors also carried out a detailed characterization of the produced materials using various techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Raman spectroscopy, Field emission scanning electron microscopy etc. The paper also present the results of the oleic acid photodegradation experiment with the use of the obtained material under UV light illumination.
The introduction part in the manuscript has been correctly written and it is an excellent introduction to the research subject. However, there is no precise formulation of the research goal and the novelty of this study in relation to the existing state of knowledge. This information should be clearly stated in the article. The research part concerning on the preparation and characterization of the TiO2 thin films has been well written. The analytical methods were appropriately selected and the obtained results were correctly interpreted and described in the paper. However, the description and results of the photocatalytic activity tests in experimental section of the manuscript is poorly written. In my opinion, these results should be definitely extended and discussed more broadly, taking into account the catalytic profile of the journal. Moreover, some of important information are missing in this section, e.g.
- Which samples were tested? The article presents the results of photocatalytic test only for one TiO2 film. (Which?)
- There is no information about the wavelength of the UV lamp during photocatalytic experiments.
- There is no information about the reagents (producer, purity, chemical formula) used during synthesis and photocatalytic experiments. This information, together with a detailed description of the photocatalytic experiment should be placed in the "experimental" section.
- The authors correctly presented obtained photocatalytic result, but the discussion was very brief.

Additionally, a few things in the article need to be corrected, including:
- The chemical formula, manufacturer and purity of all reagents used in this research should be added.
- Equation numbering should also be included in the text.
- In figure 2 there is no need to put the description "(A)" since there is only one drawing.
- The size of the fonts in Figure 4 (A) and (B) should be standardized.
- Designations in the caption of Figure 5 should be unified (a -> A ...).
- Some sentences are too long or poorly written and should be shortened/corrected for better understanding, especially in the part of the manuscript dealing with photocatalytic studies. For example, on line 224 (page 8) "Form the graph it is observed that for glass...".

Author Response

Date: 28/12/2020

To,

The Editor,

Catalysts,

     

         This is in connection with the subject mentioned below. We have revised the manuscript as per the suggestions made by reviewers and changes made in the manuscript are highlighted by yellow highlighter.

 

           Subject: Submission of revised manuscript

           Manuscript Number: Catalysts-1055183

          Title: Low Temperature Deposition of TiO2 Thin Films through Atmospheric Pressure

                    Plasma Jet Processing

 

Comments from editor and reviewer

Reviewer 1

Titanium dioxide is one of the most studied material recently due to its many interesting properties. However, this subject is still "open book" and investigations related to immobilization of TiO2 on different substrates is extremely interesting from application point of view.
The authors in the article presented the results of study on the preparation of TiO2 coatings on glass and silicon substrates by atmospheric pressure plasma jet (APPJ) technique. The effect of gases like He, Ar, water vapor and gas flow rate on the structural, morphological, optical properties of TiO2 thin films were also studied. The authors also carried out a detailed characterization of the produced materials using various techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Raman spectroscopy, Field emission scanning electron microscopy etc. The paper also present the results of the oleic acid photodegradation experiment with the use of the obtained material under UV light illumination. The introduction part in the manuscript has been correctly written and it is an excellent introduction to the research subject. However, there is no precise formulation of the research goal and the novelty of this study in relation to the existing state of knowledge. This information should be clearly stated in the article. The research part concerning on the preparation and characterization of the TiO2 thin films has been well written. The analytical methods were appropriately selected and the obtained results were correctly interpreted and described in the paper. However, the description and results of the photocatalytic activity tests in experimental section of the manuscript is poorly written. In my opinion, these results should be definitely extended and discussed more broadly, taking into account the catalytic profile of the journal. Moreover, some of important information are missing in this section, e.g.

- Which samples were tested? The article presents the results of photocatalytic test only for one TiO2 film. (Which?)

Response: Thank you for valuable comment. The photocatalytic activity tested for bare glass substrate and TiO2 film produced by APPJ technique. TiO2 film prepared using (He/Ar: 3L/min / 300 mL/min) composition of gas with H2O. Also included in revised manuscript line no. 234,235.

- There is no information about the wavelength of the UV lamp during photocatalytic experiments.

Response: Thank you for valuable comment. Black light was used during the experiment having wavelength 365 nm. Also included in the revised manuscript and highlighted in line no.119.

- There is no information about the reagents (producer, purity, chemical formula) used during synthesis and photocatalytic experiments. This information, together with a detailed description of the photocatalytic experiment should be placed in the "experimental" section.

Response: Thank you for valuable comment. Information regarding to reagents and description of the photocatalytic experiment was added in the revised manuscript and highlighted a. Also included in the revised manuscript and highlighted in line no 94 to 96 and 116 to 126.

- The authors correctly presented obtained photocatalytic result, but the discussion was very brief.

Response: Thank you for valuable comment. As per the suggestion changes made in the revised manuscript.

Additionally, a few things in the article need to be corrected, including:

- The chemical formula, manufacturer and purity of all reagents used in this research should be added.

Response: Thank you for valuable comment. Information regarding to reagents was added in the revised manuscript and highlighted in line no 94 to 96.

- Equation numbering should also be included in the text.

Response: Thank you for valuable comment. Included in the revised manuscript

- In figure 2 there is no need to put the description "(A)" since there is only one drawing.

Response: Thank you for valuable comment. Description A was removed and highlighted in line no. 143.

- The size of the fonts in Figure 4 (A) and (B) should be standardized.

Response: Thank you for valuable comment. Size of the fonts in Figure 4 (A) and (B) is standardized and highlighted by Yellow highlighter.

- Designations in the caption of Figure 5 should be unified (a -> A ...).

Response: Thank you for valuable comment. Designations in the caption of Figure 5 is unified and highlighted in line no. 203, 204 and 205.

- Some sentences are too long or poorly written and should be shortened/corrected for better understanding, especially in the part of the manuscript dealing with photocatalytic studies. For example, on line 224 (page 8) "Form the graph it is observed that for glass..."

Response: Thank you for valuable comment. As per the reviewer suggestions sentences are corrected, shortened and highlighted in the revised manuscript line no. 236 to 240 and 243 to 249.

Finally, authors are once again thankful to the reviewer for the valuable comments, which helped us improve the manuscript substantially.

Thanking you with kind regards,

 

Author Response File: Author Response.docx

Reviewer 2 Report

My recommendation is major revision as one of experiments does no have (described) control, namely the photocatalytic experiment. Despite Authors’ claim ‘which suggest that both light and catalyst is required for the effective photodegradation’ (page 9, line 233), there is no description of catalytic activity of TiO2-covered material in darkness.

Additionally, Authors should clearly describe, what is the novelty in the paper presented – method of the deposition, or maybe results obtained? Such comment should be included into introduction and conclusion parts of the article, as its absence makes difficult to judge the novelty of the research.

Author Response

                                                                                                         Date: 28/12/2020

To,

The Editor,

Catalysts,

     

         This is in connection with the subject mentioned below. We have revised the manuscript as per the suggestions made by reviewers and changes made in the manuscript are highlighted by yellow highlighter.

 

           Subject: Submission of revised manuscript

           Manuscript Number: Catalysts-1055183

          Title: Low Temperature Deposition of TiO2 Thin Films through Atmospheric Pressure

                    Plasma Jet Processing

 

Comments from editor and reviewer

Reviewer 2

My recommendation is major revision as one of experiments does no have (described) control, namely the photocatalytic experiment. Despite Authors’ claim ‘which suggest that both light and catalyst is required for the effective photodegradation’ (page 9, line 233), there is no description of catalytic activity of TiO2-covered material in darkness.

Response: Thank you for valuable comment. As per the reviewer suggestions sentences are corrected, shortened and highlighted in the revised manuscript line no. 243-249.

Additionally, Authors should clearly describe, what is the novelty in the paper presented – method of the deposition, or maybe results obtained? Such comment should be included into introduction and conclusion parts of the article, as its absence makes difficult to judge the novelty of the research.

Response: Thank you for valuable comment. As per the reviewer suggestions novelty of the present work is added and highlighted in the revised manuscript line no. 84 to 86.

Finally, authors are once again thankful to the reviewer for the valuable comments, which helped us improve the manuscript substantially.

Thanking you with kind regards,

 

Author Response File: Author Response.docx

Reviewer 3 Report

In this article, Suresh Gosavi et.al reported an atmospheric pressure plasma jet processing technique for Tio2 film deposition.  I have a few questions as follows:

  1. In the introduction part, I suggested the authors to add more information about APPJ, particularly its working principle. This will help the readers understand why the authors choose different gas and flow speed in their experiments, which are the main contents of this study.
  2. Line 86, why the authors choose the 125 oC rather than other temperature?
  3. Line 197 , Typos. Fig. 5 (D) (F) should be Fig.6 D, F
  4. Can the authors explain why the water vapor have effects on the morphology of TiO2 films?
  5. Fig. 8. The authors only use the change of contact angle as an index to show the photo degradation of oleic acid.  More characterizations should be used to get a more solid conclusion. For example, Using HPLC to  analysis of the product of oleic acid after UV irradiation.

Author Response

                                                                                                         Date: 28/12/2020

To,

The Editor,

Catalysts,

     

         This is in connection with the subject mentioned below. We have revised the manuscript as per the suggestions made by reviewers and changes made in the manuscript are highlighted by yellow highlighter.

 

           Subject: Submission of revised manuscript

           Manuscript Number: Catalysts-1055183

          Title: Low Temperature Deposition of TiO2 Thin Films through Atmospheric Pressure

                    Plasma Jet Processing

 

Comments from editor and reviewer

Reviewer 3

In this article, Suresh Gosavi et.al reported an atmospheric pressure plasma jet processing technique for TiO2 film deposition.  I have a few questions as follows:

  1. In the introduction part, I suggested the authors to add more information about APPJ, particularly its working principle. This will help the readers understand why the authors choose different gas and flow speed in their experiments, which are the main contents of this study.

Response: Thank you for valuable comment. As per the reviewer more information about APPJ is added and highlighted in the revised manuscript line no. 52 to 60.

 

  1. Line 86, why the authors choose the 125 oC rather than other temperature?

Response: Thank you for valuable comment. By referring the previous study done by the Siming Dong et al. for the deposition of conductive transparent TiNx/TiO2 hybrid films on both polycarbonate and silicon substrates using titanium ethoxide precursor by atmospheric plasma processing. (Dong et al. Adv. Funct. Mater. 24, (2014), 3075-3081

 

  1. Line 197 , Typos. Fig. 5 (D) (F) should be Fig.6 D, F

Response: Thank you for valuable comment. We corrected the figure numbers and highlighted in the revised manuscript in line no. 210.

 

  1. Can the authors explain why the water vapor have effects on the morphology of TiO2 films?

Response: Thank you for valuable comment. During the deposition of TiO2 water vapor is considered as reactive gas. The rapid formation of anatase phase can be only due to the interaction of water vapor molecules with the amorphous TiO2. Unlike what happens in the liquid water, the molecules in the gas are not in strong interaction with each other. This allows greater freedom to the water molecules to fill better and faster a porous structure as the TiO2. Consequently they can increase the adsorption rate onto the amorphous titania surface, dramatically increasing the rate of crystallization. This fact is supported by Raman and SEM results. Also water contact angle exponentially decreases from slightly hydrophobic for the amorphous TiO2 to super hydrophilic during the photocatalytic experiment. The enhanced wettability can be ascribed to the water vapor interaction, which is responsible for the introduction of a high number of surface defects, acting as adsorption sites for –OH groups. Furthermore, this increased wetting behaviour can be considered as a co-responsible for the rapid crystallization of the material during the interaction with the water vapor. In fact, the steam exposure significantly increases the wettability and consequently the interaction between water (catalyzing agent of crystallization) and the surface of TiO2 (gradually more and more crystalline) gets stronger [1,2,3].

References

1] Bally A. Electronic properties of nano-crystalline titanium dioxide thin films, Thèse No 2094, École Polytechnique Fédérale de Lausanne; 1999. p. 76.

2] Lamberti, A., Chiodoni, A., Shahzad, N. et al. Ultrafast Room-Temperature Crystallization of TiO2 Nanotubes Exploiting Water-Vapor Treatment. Sci Rep 5, 7808 (2015).

3] Zurek J., Michalik M., Schmitz F., Kern T. U., Singheiser L., Quadakkers W. J., The Effect of Water-Vapor Content and Gas Flow Rate on the Oxidation Mechanism of a 10%Cr-Ferritic Steel in Ar-H2O Mixtures, Oxid Met., (2005), 401–422

 

  1. Fig. 8. The authors only use the change of contact angle as an index to show the photo degradation of oleic acid.  More characterizations should be used to get a more solid conclusion. For example, Using HPLC to analysis of the product of oleic acid after UV irradiation.

Response: Thank you for valuable comment. Photocatalytic degradation experiments were conducted according to Japanese Industrial Standard (JIS 1703-1) (ISO/PIS 27448-1). So it confirms and supports the photocatalytic decomposition of oleic acid. 

Finally, authors are once again thankful to the reviewer for the valuable comments, which helped us improve the manuscript substantially.

Thanking you with kind regards,

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you for providing updated version of the manuscript.

Despite your response, I didn't find description of control experiment of oleic acid decomposition in the absence of light. Did you perform such experiment?

 

Authors didn't change anything in the 'Conclusions' part, where comment on the novelty of this study should be placed.

Author Response

Date: 31/12/2020

To,

The Editor,

Catalysts,

     

         This is in connection with the subject mentioned below. We have revised the manuscript as per the suggestions made by reviewers and changes made in the manuscript are highlighted by yellow highlighter.

 

           Subject: Submission of revised manuscript

           Manuscript Number: Catalysts-1055183R1

          Title: Low Temperature Deposition of TiO2 Thin Films through Atmospheric Pressure

                    Plasma Jet Processing

 

Comments from editor and reviewer

Reviewer 2

1) Despite your response, I didn't find description of control experiment of oleic acid decomposition in the absence of light. Did you perform such experiment?

Response: Thank you for valuable comment. In the absence of light, the oleic acid did not decompose. Therefore, the water contact angle did not change during the experiment. To make the figure simple, we did not include the result.

 

2) Authors didn't change anything in the 'Conclusions' part, where comment on the novelty of this study should be placed.

Response: Thank you for valuable comment. As per the reviewer suggestions novelty of the present work is added in the conclusions part and highlighted in the revised manuscript line no. 252 to 256.

Finally, authors are once again thankful to the reviewer for the valuable comments, which helped us improve the manuscript substantially.

Thanking you with kind regards,

Author Response File: Author Response.docx

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