Ceramic ZnO-SnO₂-Fe₂O₃ Powders and Coatings -Effective Photogenerators of Reactive Oxygen Species

Round 1

Reviewer 1 Report

Please, see the attachment.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

1) Every abstract should only contain relevant information that summarizes the work; terms like “additionally"... are useless. Also adds quantitative information to the summary if relevant. I recommend authors use the following reference to adjust their abstract (https://doi.org/10.1016/j.carbon.2007.07.009).

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript demonstrates the dye degradation ability of doped ZnO films deposited using the polymer-salt synthesis technique. Given the ubiquity and industrial usefulness of ZnO and the unique composition reported here, the paper can be published subject to addressing a few shortcomings:

Can the authors present the chemical formula for their ZnO-based compound? The way it is presented in the manuscript currently is quite confusing. The notion of ZnO-SnO₂-Fe₂O₃ may imply a composite material. However, the XRD result shows a single phase, implying that Fe and Sn ions were probably doped at the Zn site within the ZnO lattice. A notation like Zn_xSn_yFe_zO is scientifically more accurate.

Can authors explain the shift in the most intense XRD peak in the deposited film (002), compared to the one of powder ZnO (101)? Has there been a preferred growth axis? Full Rietveld refinement can be very beneficial for analyzing the XRD result.

Can the authors elaborate on the Fe and Sn oxidation state within the ZnO lattice? Fe can be either 2+ or 3+, while Sn can commonly be either 3+ or 4+. Which one of these dopants has a greater effect on the observed photo-degradation capacity? Transition metals dopants are known to be very potent in favorably altering ZnO’s band structure and density of states near the Fermi level:

Assadi et al. J. Appl. Phys. 111, 113901 (2012); https://doi.org/10.1063/1.4719977

Accordingly, the photocatalytic activity may be explained by the unpaired electrons of the Fe ion.

Finally, some recent literature regarding the well-characterized dye degradation activity of ZnO can be discussed and cited, showcasing the significance of this research topic:

Doustkhah et al. Chemosphere, 303, 2022, 134932; https://doi.org/10.1016/j.chemosphere.2022.134932

 

“ROS” was used in the abstract without definition. Abstracts are better off without acronyms and abbreviations.

Author Response

 

Dear Reviewer!

Thank you for detailed consideration of our article. We made significant changes in the text according to your notes. All changes were marked by green color.

Can the authors present the chemical formula for their ZnO-based compound? The way it is presented in the manuscript currently is quite confusing. The notion of ZnO-SnO₂-Fe₂O₃ may imply a composite material. However, the XRD result shows a single phase, implying that Fe and Sn ions were probably doped at the Zn site within the ZnO lattice. A notation like Zn_xSn_yFe_zO is scientifically more accurate.

Ionic radii of Zn²⁺, Sn⁴⁺ and Fe³⁺ (or Fe²⁺) ions are different. Therefore, the introduction of doping ions into the ZnO crystals lattice should accompanying by the shifts of peaks positions in XRD patterns. However, this shift is not observed in obtained XRD patterns.  In our previous work (Khomutinnikova, L.L.; Evstropiev, S.K.; Danilovich, D.P.; Meshkovskii, I.K.; Bulyga, D.V. Structural engineering of photocatalytic ZnO-SnO₂-Fe₂O₃ composites. J. Comp. Sci, 2022, 6, 331. https://doi.org/10.3390/jcs6110331.) powder materials of the system ZnO-SnO₂-Fe₂O₃ with the different content of SnO₂ and Fe₂O₃ were synthesized and studied. In XRD patterns of ZnO-based powders containing relatively high contents of additions (SnO₂ 3 mol.% + Fe₂O₃ 10 mol.%) a lot of peaks corresponding to different crystals (ZnO; SnO₂; Zn₂SnO₄; ZnFe₂O₄) were observed. This fact suggests additionally that the ceramic powder and thin coating prepared in the present work are composites and the embedding of Sn and Fe into the lattice of ZnO crystals isn’t significant.

Can authors explain the shift in the most intense XRD peak in the deposited film (002), compared to the one of powder ZnO (101)? Has there been a preferred growth axis? Full Rietveld refinement can be very beneficial for analyzing the XRD result.

The orientation of ZnO crystals in the direction (002) is well-known phenomenon described in the literature. The mechanism of this orientation is related to the strong interaction of forming ZnO crystal with the substrate surface. In article we have described this phenomenon with corresponding references (page 4).

Can the authors elaborate on the Fe and Sn oxidation state within the ZnO lattice? Fe can be either 2+ or 3+, while Sn can commonly be either 3+ or 4+. Which one of these dopants has a greater effect on the observed photo-degradation capacity? Transition metals dopants are known to be very potent in favorably altering ZnO’s band structure and density of states near the Fermi level: Assadi et al. J. Appl. Phys. 111, 113901 (2012); https://doi.org/10.1063/1.4719977

Accordingly, the photocatalytic activity may be explained by the unpaired electrons of the Fe ion.

You are right that structural defects and doping components change the electronic structure of ZnO crystals that significantly affects their photocatalytic properties.

However, it is difficult to elaborate Fe and Sn oxidation state in our materials. In XRD patterns of ZnO-based powders containing relatively high contents of additions (SnO₂ 3 mol.% + Fe₂O₃ 10 mol.%) a lot of peaks corresponding to SnO₂; Zn₂SnO₄; ZnFe₂O₄ were observed. Clearly, that in these compounds the valent forms of Sn and Fe are +4 and +3, correspondingly.

Finally, some recent literature regarding the well-characterized dye degradation activity of ZnO can be discussed and cited, showcasing the significance of this research topic: Doustkhah et al. Chemosphere, 303, 2022, 134932; https://doi.org/10.1016/j.chemosphere.2022.134932.

Thank you for this reference. Very interesting results. We have added this reference into our article.

 “ROS” was used in the abstract without definition. Abstracts are better off without acronyms and abbreviations.

We removed the abbreviation “ROS” from the abstract.

Thank you for your work.

 

Best regards,

 

Evstropiev S.K.

 

Round 2

Reviewer 1 Report

The authors made the necessary modifications. The manuscript can be accepted for publication in the form presented.

Reviewer 2 Report

The authors have responded to the comments and revised it throughout the manuscript. It can be published in the current format.