Time-Dependent Hydrothermal Synthesis of TiO₂ in the Presence of Zn²⁺: Effects on Photoconductivity

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Major revisions are suggested for this manuscript:

1. Figure 1 can be deleted.
2. While XRD shows no Zn-related phases, no surface analysis (such as XPS or EDS) is provided to confirm whether Zn is doped into the lattice or merely adsorbed on the surface. Additional elemental and chemical state analysis is needed to clarify the form and distribution of Zn.
3. The proposed role of oxygen vacancies and Ti³⁺ states lacks direct evidence (e.g., EPR, XPS, or PL spectroscopy). PLease incorporate the defect-specific characterization to strengthen the mechanistic claims.
4. The light source intensity is given (240 W/m²), but the spectral range and any filters used are not specified. Please provide full details of the illumination conditions to ensure reproducibility.
5. Light on/light off should be marked in the photoconductivity results Figure 6 and 8.
6. Similar to conductivity, photocurrent responses of the desiged materials can be also measured, which can help explain the mechanism. please refer to DOI: 10.1039/d4ta06083k.
7. Although comparisons are made with P25, a more systematic comparison with other modified TiO₂ systems (e.g., La-doped, plasma-treated, or other metal-modified TiO₂) would better contextualize the performance of the synthesized materials. A comparative table or extended discussion is recommended.
8. The conclusion does not sufficiently highlight the novelty or specific advantages of the Zn/time synergy compared to existing studies. Please clearly articulate the unique contributions of this work and its potential applications in photocatalysis and photoelectrochemistry. 

Author Response

Dear reviewer 

Thank you very much for taking the time to review our manuscript and for providing insightful and constructive feedback to help improve its quality for publication. This document contains our detailed responses to each of your comments. A revised version of the manuscript, with all modifications clearly marked and underlined, is included in the accompanying PDF file.

 Comments 

Point 1: Figure 1 can be deleted. 

• Response 1: Figure was revised.

Point 2: While XRD shows no Zn-related phases, no surface analysis (such as XPS or EDS) is provided to confirm whether Zn is doped into the lattice or merely adsorbed on the surface. Additional elemental and chemical state analysis is needed to clarify the form and distribution of Zn. 

• Response 2: As stated in the manuscript, the Zn+2 ions from ZnSO4 act as a reducing agent to create oxygen vacancies during synthesis. After the reaction, the Zn is removed during washing. The enhanced photoconductivity of the final material provides direct evidence for the presence of these oxygen vacancies, which act as a form of self-doping in the TiO2 lattice.

Point 3: The proposed role of oxygen vacancies and Ti+3 states lack direct evidence (e.g., EPR, XPS, or PL spectroscopy). Please incorporate the defect-specific characterization to strengthen the mechanistic claims. 

• Response 3: We agree that techniques like EPR and XPS provide direct characterization of defects. In this work, however, we rely on the established role of Zn+2 ions as a reducing agent to create oxygen vacancies, as supported by literature. The formation of these vacancies is confirmed indirectly by the measured increase in photoconductivity, which is a key functional outcome of such defects.

Point 4: The light source intensity is given (240 W/m2), but the spectral range and any filters used are not specified. Please provide full details of the illumination conditions to ensure reproducibility. 

• Response 4: Lines 128–130 have been revised in accordance with the reviewers’ suggestion.

Point 5: Light on/light off should be marked in the photoconductivity results Figure 6 and 8. 

• Response 5: Figure has been revised in accordance with the reviewers’ suggestion.

Point 6: Similar to conductivity, photocurrent responses of the designed materials can be also measured, which can help explain the mechanism. please refer to DOI: 10.1039/d4ta06083k. 

• Response 6: In this study, transient photoconductivity measurements were performed, which directly probe charge carrier dynamics and recombination processes. Photocurrent measurements, although informative, are strongly dependent on sample geometry and contact configuration, whereas photoconductivity reflects the intrinsic electronic response of the material. The reference suggested by the reviewer (DOI: 10.1039/d4ta06083k) has been added in the introduction section.

Point 7: Although comparisons are made with P25, a more systematic comparison with other modified TiO2 systems (e.g., La-doped, plasma-treated, or other metal-modified TiO2) would better contextualize the performance of the synthesized materials. A comparative table or extended discussion is recommended. 

• Response 7: In the final section of the discussion, Table 8 presents a comparison of our results with those reported in the literature, focusing on the photoconductivity parameter obtained using different synthesis methods. The P25 curve in the photoconductivity plots serves as the baseline for our results, while Table 8 provides the main comparative analysis.

Point 8: The conclusion does not sufficiently highlight the novelty or specific advantages of the Zn/time synergy compared to existing studies. Please clearly articulate the unique contributions of this work and its potential applications in photocatalysis and photo electrochemistry. 

• Response 8: The last paragraph of the Introduction section was revised for better clarity.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The fabrication and study of wide-gap semiconductor materials with improved structural, electrical, and catalytic properties is a required area of scientific and engineering investigation in recent decades. Titania (TiO₂) is the most popular and well-studied material in this group, therefore, articles about titania must contain a high level of novelty and originality. Certainly, the obtaining of nanostructured materials including nanoparticles is required, but the experiment must be conducted correctly, and the results must be presented according to academic standards. As it is currently written, the manuscript does not meet the modern demands of the scientific community. The following comments and suggestions that will help the authors improve their work and its presentation.  

1. In the Introduction part section, references to new articles (from the last 3 years) should be used to emphasize the relevance of the work and highlight the latest achievements.
2. Figure 1 must be redone. The photos near the scheme are unclear and unmotivated. The level of graphics in the scheme is extremely low. What does the bottom photo mean? Ununderstandable.
3. Neither the synthesis description nor Table 1 contains information on the purity or pre-cleaning of the reagents used.
4. The motivation of using only two concentrations of the dopant in synthesis and temperature regimes is unclear. Additionally, if the authors choose to double the Zn concentration, why the then choose to increase the reaction time by 2.4 times?
5. The link to Table 8 in line 120 is irrelevant. According to the description in text, I suppose the authors mean Table 2.
6. According to the XRD results and the authors’ comments, Zn was completely removed from the composite during the washing process. However, the part of the title “…Synthesis of Zn²⁺-Modified TiO₂…” creates the impression that the composite material is being received. Therefore, the title must be adjusted. For the same reason, phrases such as “Zn-modified” should be avoided, as they also create the impression of a composite study.
7. Table 3 shows the Sherrer analysis for the three peaks of TiO₂. However, the (004) plane reflection peak consists of three components, according to [JCPDS No. 73-1764] authors provide. The data about fitting or averaging, or other processing of the ternary peak is absent.
8. The interpretation of the XRD results represented in the Table 3 is confusing and incomprehensible. Particularly, values 15.5 and 16.6 nm are absent in Table 3 (line 155), as well as 20 nm. If the authors used average values, they should indicate this and provide the calculation of the averages. Furthermore, to discuss growth trends, the error margin in calculating the average crystallite size must be provided.
9. The result subsections should highlight the fact that Zn was only added during the synthesis process. For example, line 168 read: “With the addition of 4%Zn and 8%Zn, the average particle size decreases to…” should be corrected to read “With the addition of Zn during the synthesis process…”, or like this.
10. Analysis of average particle sizes on SEM images is best done using specialized software that provides better visualization.
11. For better understanding in Fig. 4 (b) and (d), the determination of the band gap energies using the Kubelka–Munk function must be built as an insert with a detailed scale, probably, from 3.0 up to 3.6 eV on the abscissa axis.
12. The pore size distribution will be more informative and easier to understand, if it is presented in the form of distribution diagram.
13. Fig. 6 raises questions and doubts about the authenticity of the data provided due to the use of two colors on the graphs for the recession area. Please check the results. For a correct presentation of the results, it is also advisable to provide references on each graph.
14. There are many theories about role of Ti³⁺ sites in the improving photoconductivity, but they do not provide clear information on how and why the presence of zinc from zinc sulfide allows oxygen defects during the synthesis process.
15. Check the degree index in line 254.
16. The authors focused on the shape of the photoconductivity peaks in their description of the results obtained in a vacuum. However, in the case of air photoconductivity, the difference in the peak form between the “pure” and “Zn” TiO₂ materials is significant. Yet, the authors did not address this in the discussion.
17. Why is photoconductivity the only parameter for comparison of the obtained TiO₂ in the Table 8? It would be more accurate to find comparisons for each parameter. Furthermore, it is inappropriate to compare the parameters for zinc-doped materials and heterostructures containing zinc oxide with the results of the current study, as the authors explicitly state that zinc is not present in the final product.
18. A basic experiment on photocatalytic activity could corroborate the conclusions of the study on improving material characteristics comprehensively using zinc-assisted synthesis.

Thus, the authors must revise their manuscript seriously so that it can be accepted by the Journal and published. I have no doubt that they will make the necessary efforts and improve the presentation of their work, as well as conduct additional studies, particularly those involving different zinc concentrations and synthesis times, etc. After these revisions, the manuscript will be able to adequately present their research and grace the pages of the Journal.

Author Response

Dear reviewer 

Thank you very much for taking the time to review our manuscript and for providing insightful and constructive feedback to help improve its quality for publication. This document contains our detailed responses to each of your comments. A revised version of the manuscript, with all modifications clearly marked and underlined, is included in the accompanying PDF file. 

Comments 

Point 1: In the Introduction section, references to new articles (from the last 3 years) should be used to emphasize the relevance of the work and highlight the latest achievements 

• Response 1: The manuscript was thoroughly revised, and recent references were incorporated in accordance with the reviewers’ suggestions.

Point 2: Figure 1 must be redone. The photos near the scheme are unclear and unmotivated. The level of graphics in the scheme is extremely low. What does the bottom photo mean?  

• Response 2: Figure was revised.

Point 3: Neither the synthesis description nor Table 1 contains information on the purity or pre-cleaning of the reagents used. 

• Response 3: Table 1 was revised to incorporate the reviewer’s suggestion.

Point 4: The motivation of using only two concentrations of the dopant in synthesis and temperature regimes is unclear. Additionally, if the authors choose to double the Zn concentration, why the then choose to increase the reaction time by 2.4 times? 

• Response 4: We thank the reviewer for this observation. The hydrothermal durations of 10 h and 24 h were adopted following the procedure reported in Ref.:

        Zhao, Z.; Sun, Z.; Zhao, H.; Zheng, M.; Du, P.; Zhao, J.; Fan, H. Phase control of hierarchically structured mesoporous anatase TiO 2 microspheres covered with {001} facets.  Journal of Materials Chemistry 2012, 404         22, 21965–21971.

Zn amounts of 4% and 8% were selected to examine how small additions of Zn influence the structural and photoconductive behavior of TiO₂, as low levels are commonly used in the literature to avoid secondary phases and highlight defect-related effects.

Point 5: The link to Table 8 in line 120 is irrelevant. According to the description in text, I suppose the authors mean Table 2. 

• Response 5: Corrected.

Point 6: According to the XRD results and the authors’ comments, Zn was completely removed from the composite during the washing process. However, the part of the title “…Synthesis of Zn²⁺-Modified TiO₂…” creates the impression that the composite material is being received. Therefore, the title must be adjusted. For the same reason, phrases such as “Zn-modified” should be avoided, as they also create the impression of a composite study. 

• Response 6: We agree with the reviewer’s comment and accordingly we have revised the title.
  In addition, we have replaced the expressions “modified” and “modification” throughout the manuscript with more accurate wording to avoid any misunderstanding.

Point 7: Table 3 shows the Sherrer analysis for the three peaks of TiO₂. However, the (004) plane reflection peak consists of three components, according to [JCPDS No. 73-1764] authors provide. The data about fitting or averaging, or other processing of the ternary peak is absent. 

• Response 7: According to JCPDS No. 73-1764, the (004) reflection can indeed contain multiple subcomponents. In our analysis, we applied peak fitting to evaluate the broadening of the (004) peak. As also noted in Ref.:

         Wee-Jun Ong, Lling-Lling Tan, Siang-Piao Chai, Siek-Ting Yong and Abdul Rahman Mohamed, Highly reactive {001} facets of TiO2-based composites: synthesis, formation mechanism and characterization, Nanoscale, 2014, 6, 1946, DOI: 10.1039/c3nr04655a.

          The Correspondence paragraph was revised and rephrased to enhance clarity.

Point 8: The interpretation of the XRD results represented in Table 3 is confusing and incomprehensible. Particularly, values 15.5 and 16.6 nm are absent in Table 3 (line 155), as well as 20 nm. If the authors used average values, they should indicate this and provide the calculation of the averages. Furthermore, to discuss growth trends, the error margin in calculating the average crystallite size must be provided. 

• Response 8: The crystallite size errors were rigorously calculated using error propagation based on the uncertainty in the FWHM values provided by the XRD analysis software and the Scherrer equation. These calculated errors are now presented in the revised Table 3, confirming the significance of the observed growth trends. Also, the text was revised.

Point 9: The result subsections should highlight the fact that Zn was only added during the synthesis process. For example, line 168 read: “With the addition of 4%Zn and 8%Zn, the average particle size decreases to…” should be corrected to read “With the addition of Zn during the synthesis process…”, or like this 

• Response 9: Corrected.

Point 10: Analysis of average particle sizes on SEM images is best done using specialized software that provides better visualization. 

• Response 10: The particle size analysis was performed directly on the SEM images using the instrument's scale bar. Measurements were taken manually for a statistically significant number of particles to ensure representative sampling. This approach provides reliable size distribution data for the purposes of our comparative analysis and is consistent with established methodologies in the field.

Point 11: For better understanding in Fig. 4 (b) and (d), the determination of the band gap energies using the Kubelka–Munk function must be built as an insert with a detailed scale, probably, from 3.0 up to 3.6 eV on the abscissa axis. 

• Response 11: Figures were revised to incorporate the reviewer’s suggestion.

Point 12: The pore size distribution will be more informative and easier to understand, if it is presented in the form of distribution diagram. 

• Response 12: The quality of the pore size distribution diagrams presented in Fig. 5 b and d was improved.

Point 13: Fig. 6 raises questions and doubts about the authenticity of the data provided due to the use of two colors on the graphs for the recession area. Please check the results. For a correct presentation of the results, it is also advisable to provide references for each graph. 

• Response 13: As described in line 242, the photoconductivity decay data were fitted to determine the trap energy depth, with the fitting curve already displayed in Figure 6. To enhance clarity, we added the fitting curve as a separate inset.

Point 14: There are many theories about role of Ti³⁺ sites in improving photoconductivity, but they do not provide clear information on how and why the presence of zinc sulfide allows oxygen defects during the synthesis process. 

• Response 14: The correspondence paragraph was revised for better clarity. Our explanation is based on the two references shown below.

        [1]  Si, L.; Huang, Z.; Lv, K.; Tang, D.; Yang, C. Facile preparation of Ti3+ self-doped TiO2 nanosheets with dominant {0 0 1} facets using zinc powder as reductant. Journal of alloys and compounds 2014, 601, 88–93.

        [2]  Zheng, Z.; Huang, B.; Meng, X.; Wang, J.; Wang, S.; Lou, Z.; Wang, Z.; Qin, X.; Zhang, X.; Dai, Y. Metallic zinc-assisted synthesis of Ti 3+ self-doped TiO 2 with tunable phase composition and visible-light photocatalytic activity. Chemical Communications 2013, 49, 868–870.

Point 15: Check the degree index in line 254. 

• Response 15:

Point 16: The authors focused on the shape of the photoconductivity peaks in their description of the results obtained in a vacuum. However, in the case of air photoconductivity, the difference in the peak form between the “pure” and “Zn” TiO₂ materials is significant. Yet, the authors did not address this in the discussion. 

• Response 16: The Correspondence paragraph was revised for better clarity.

Point 17: Why is photoconductivity the only parameter for comparison of the obtained TiO₂ in Table 8? It would be more accurate to find comparisons for each parameter. Furthermore, it is inappropriate to compare the parameters for zinc-doped materials and heterostructures containing zinc oxide with the results of the current study, as the authors explicitly state that zinc is not present in the final product. 

• Response 17: The reviewer’s comment about removing the comparison with doped materials is valid, and this has been revised accordingly in Table 8. Regarding the choice of photoconductivity as the primary parameter, this decision aligns with the focus of our study, as stated in the title. The main purpose of the comparison table is to illustrate how this parameter varies with different synthesis processes, as referenced in the manuscript.

Point 18: A basic experiment on photocatalytic activity could corroborate the conclusions of the study on improving material characteristics comprehensively using zinc-assisted synthesis. 

• Response 18: We agree that photocatalytic activity could enhance our study. However, it extends beyond the scope of this work, which focuses on optical properties. We have added a note in the conclusion highlighting photocatalytic performance as an important direction for future work.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Reviewer’s comment to authors:

In this manuscript, the authors report hydrothermal synthesis of TiO₂ powders (10 h and 24 h) with 0/4/8% ZnSO₄ modifier, characterization (XRD, SEM, BET, UV-Vis), and photoconductivity measured in vacuum and air. Key claims: (i) exclusive anatase formation, (ii) Zn and longer hydrothermal time tune crystallite/particle size and porosity, (iii) Zn + 24 h produce oxygen vacancies/Ti³⁺ that strongly enhance photoconductivity under vacuum (up to ~5 orders of magnitude versus dark and ~30× vs P25). The manuscript is interesting, but it makes some overstated claims given the available data. The introduction is overly long and includes detailed background on natural dyes that could be shortened.

 

1. Insufficient evidence for oxygen vacancies / Ti³⁺ and the role of Zn
   • The core mechanistic claim is that Zn incorporation (and longer hydrothermal time) creates oxygen vacancies/Ti³⁺ that explain the huge increase in σₚ under vacuum. However, the manuscript lacks direct, spectroscopic evidence for Ti³⁺ or O-vacancies.
   • Required additional measurements: at minimum X-ray photoelectron spectroscopy (XPS) to show Ti³⁺ signature and Zn chemical state; electron paramagnetic resonance (EPR) to detect unpaired electrons associated with oxygen vacancies; and/or XANES/EXAFS to probe Ti oxidation state. Without these, the causative link is speculative.
2. XRD shows only anatase and no Zn phases — the authors say Zn was likely washed away. If Zn is not retained, how can it be invoked as the cause of defect engineering? The presence (or absence) of Zn in final powders must be quantified (ICP-OES or ICP-MS) and surface composition checked (XPS). If Zn concentration is below the XRD detection limit but still influential at the surface, that should be explicitly demonstrated.
3. In Table 6, for TS10, the σp2 (5.96×10⁻⁷) is lower than σp1 (3.55×10⁻⁴) — this looks like a units/typo error (and inconsistent with other samples where σp2 > σp1). Authors must confirm numbers and units. Provide consistent significant figures and scientific notation throughout.
4. To validate that photoconductivity enhancement arises from decreased recombination via vacancies, perform complementary transient optical/PL measurements: time-resolved photoluminescence (TRPL), transient absorption (TA), or photocurrent rise/decay fits with reported τ values and fit quality. Also cite the following papers: Journal of Alloys and Compounds 786 (2019) 750-757 and Solar Energy 174 (2018) 231–239.
5. Sample preparation: pellet pressing pressure, pellet density, thickness, electrode contact resistance, and whether electrodes were reused must be specified. Are the silver contacts stable and ohmic? Show I–V curves demonstrating linear (ohmic) behavior with the actual contact geometry.

Author Response

Dear reviewer 

Thank you very much for taking the time to review our manuscript and for providing insightful and constructive feedback to help improve its quality for publication. This document contains our detailed responses to each of your comments. A revised version of the manuscript, with all modifications clearly marked and underlined, is included in the accompanying PDF file.

 Comments 

Point 1: Insufficient evidence for oxygen vacancies / Ti³⁺ and the role of Zn. The core mechanistic claim is that Zn incorporation (and longer hydrothermal time) creates oxygen vacancies/Ti³⁺ that explain the huge increase in σₚ under vacuum. However, the manuscript lacks direct, spectroscopic evidence for Ti³⁺ or O-vacancies. Required additional measurements: at minimum X-ray photoelectron spectroscopy (XPS) to show Ti³⁺ signature and Zn chemical state; electron paramagnetic resonance (EPR) to detect unpaired electrons associated with oxygen vacancies; and/or XANES/EXAFS to probe Ti oxidation state. Without these, the causative link is speculative. 

• Response 1: As stated in the manuscript, the Zn²⁺ ions from ZnSO₄ act as a reducing agent to create oxygen vacancies during synthesis. After the reaction, the Zn is removed during washing. The enhanced photoconductivity of the final material provides direct evidence for the presence of these oxygen vacancies, which act as a form of self-doping in the TiO₂ lattice. We agree that techniques like EPR and XPS provide direct characterization of defects. In this work, however, we rely on the established role of Zn²⁺ ions as a reducing agent to create oxygen vacancies, as supported by literature. The formation of these vacancies is confirmed indirectly by the measured increase in photoconductivity, which is a key functional outcome of such defects. A few lines were added to the Conclusion section to highlight this point.

Point 2: XRD shows only anatase and no Zn phases — the authors say Zn was likely washed away. If Zn is not retained, how can it be invoked as the cause of defect engineering? The presence (or absence) of Zn in final powders must be quantified (ICP-OES or ICP-MS) and surface composition checked (XPS). If Zn concentration is below the XRD detection limit but still influential at the surface, that should be explicitly demonstrated. 

• Response 2: As stated in our manuscript, Zn acts as a reducing agent during synthesis, promoting the formation of oxygen vacancies, in agreement with literature. The enhanced photoconductivity we measure in the final material provides direct functional evidence for these vacancies, which remain active in the TiO₂ lattice after Zn removal during washing.

Point 3: In Table 6, for TS10, the σp2 (5.96×10⁻⁷) is lower than σp1 (3.55×10⁻⁴) — this looks like a units/typo error (and inconsistent with other samples where σp2 > σp1). Authors must confirm numbers and units. Provide consistent significant figures and scientific notation throughout. 

• Response 3: Table 6 was corrected.

Point 4: To validate that photoconductivity enhancement arises from decreased recombination via vacancies, perform complementary transient optical/PL measurements: time-resolved photoluminescence (TRPL), transient absorption (TA), or photocurrent rise/decay fits with reported τ values and fit quality. Also cite the following papers: Journal of Alloys and Compounds 786 (2019) 750-757 and Solar Energy 174 (2018) 231–239. 

• Response 4: Time-resolved techniques like TRPL would indeed offer deeper insight into carrier dynamics. In our work, we rely on the well-established interpretation of photoconductivity changes in different atmospheres as evidence for reduced recombination. The drastic enhancement in photoconductivity (σₚ) under vacuum is a classic signature of reduced charge carrier recombination, as the absence of O₂ prevents the re-capture of electrons from the vacancy states. The reversal of this effect in air directly demonstrates how adsorbed O₂ quenches the charge carriers associated with these vacancies, effectively increasing recombination. We have incorporated the suggested references into our introduction.

Point 5: Sample preparation: pellet pressing pressure, pellet density, thickness, electrode contact resistance, and whether electrodes were reused must be specified. Are the silver contacts stable and ohmic? Show I–V curves demonstrating linear (ohmic) behavior with the actual contact geometry. 

• Response 5: The correspondence paragraph was revised and rephrased to enhance clarity. In addition, we now present the I–V plots, shown here for the representative TS24 sample, to demonstrate the ohmic behavior observed in all samples. These graphs were not included in the main text of the manuscript to avoid overloading it with figures; however, the ohmic nature of the contacts is clearly stated and discussed in the text.

 

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Accept in present form

Author Response

Kindly see the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article was improved by the addition and correction of information based on comments, as well as the expansion of the bibliography. I would like to express my gratitude to the authors for their accurate rewrite of the manuscript.

Some comments were formally taken into account. Nevertheless, improvement is still needed in these areas.

1. On Fig. 1, check the subscript in the chemical formulas.
2. Just as the authors justified the heat treatment time during synthesis by adding a source reference, they should also justify the zinc concentration. Please correct this.
3. Figure 5 remains unchanged in its clarity. I'm providing an example article from https://doi.org/10.3390/ma12091485 for reference only, not for citation purposes. Note the pore distribution representation in the form of a histogram in Figure 5 of the linked article. This type of visual representation will improve your manuscript and demonstrate that your material is uniformly structured. Please redo your figure to ensure the best presentation of your results.

Once these minor corrections have been made, the article will be ready for publication.

Author Response

Dear reviewer 

We sincerely thank you for your positive evaluation of our manuscript and for recommending it for publication after minor corrections. We are very grateful for your thoughtful comments and suggestions, which have helped us further improve the quality and clarity of our work. In accordance with your feedback, we have carefully made all the requested changes. 

Comments 

Point 1: On Fig. 1, check the subscript in the chemical formulas. 

• Response 1: Corrected.

Point 2: Just as the authors justified the heat treatment time during synthesis by adding a source reference, they should also justify the zinc concentration. Please correct this. 

• Response 2: A few lines have been added to the manuscript along with the corresponding references.

Point 3: Figure 5 remains unchanged in its clarity. I'm providing an example article from https://doi.org/10.3390/ma12091485 for reference only, not for citation purposes. Note the pore distribution representation in the form of a histogram in Figure 5 of the linked article. This type of visual representation will improve your manuscript and demonstrate that your material is uniformly structured. Please redo your figure to ensure the best presentation of your results. 

• Response 3: Figure 5 was revised in accordance with the reviewers’ suggestion.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Authors responded to most of the comments. However, they still need to find out the rise and decay times.

Author Response

Dear reviewer 

We sincerely thank you for your positive evaluation of our manuscript and for recommending it for publication after minor corrections. We are very grateful for your thoughtful comments and suggestions, which have helped us further improve the quality and clarity of our work. In accordance with your feedback, we have carefully made the requested change. 

Comments 

Point 1: Authors responded to most of the comments. However, they still need to find out the rise and decay times. 

• Response 1: Table 6 has been revised to incorporate the reviewer’s suggestion.

Author Response File: Author Response.pdf