Plasmonic Photocatalysts Based on Au Nanoparticles and WO₃ for Visible Light-Induced Photocatalytic Activity

Round 1

Reviewer 1 Report

 

Reviewer#1

  M. Desseigne   et al has been repoted work “Au nanoparticles and WO3 for visible light induced photocatalytic activity” is very suitable for this journal. As proposed applications are very interesting therefore I recommended in this work and I declared some comments for before acceptance.

1. In introduction section, the author should be compared to the previous reported Au nanoparticles. Such as https://doi.org/10.1016/j.optmat.2021.111945; https://doi.org/10.1007/s42452-018-0148-y ;  and https://doi.org/10.1016/j.cplett.2019.137050.

2.  The author used for two different methods but why morphology did not change? What is the reason?

3. Line 313 some corrections is there please check it.

4.  The photocatalytic dye degradation results should be compared other reported materials.

5. The author should be carried out catalyst stability and reusability studies.

6.  Which type of the band gap is appeared in optical properties?

7. Subtitle 3.4, the authors includes the blank samples investigation.

8. How did you confirm M-O orientations, if possible please carried out the FTIR study?

9. Improved to the Figures resolution.

10.  Carefully check to the typo and topo graphical errors.

 

Comments for author File: Comments.pdf

Good

Author Response

  Dear reviewer,

I'd like to thank you for reviewing this article, and also thank you for your pertinent and constructive criticism.

1. In introduction section, the author should be compared to the previous reported Au nanoparticles. Such as https://doi.org/10.1016/j.optmat.2021.111945; https://doi.org/10.1007/s42452-018-0148-y;  and https://doi.org/10.1016/j.cplett.2019.137050.

• The references are added and commented in the introduction, except for the reference https://doi.org/10.1016/j.cplett.2019.137050. The latter deals with the ZnSnO₃/rGO composite, a completely different system from the material we have proposed (WO₃/Au NPs).

Despite the very interesting photocatalysis results discussed in the article https://doi.org/10.1016/j.optmat.2021.111945, the points discussed from the point of view of physicochemical characterization or properties of metallic materials (gold particles) are not in agreement with our article.

2. The author used for two different methods but why morphology did not change? What is the reason?

• Yes, the morphology changes. As you can see from the TEM and SEM images (see figures 3b and 3d), using two different precursors’ results in two morphologies, one platelet-shaped and the other formless (quasi-spherical).

The use of these two precursors in aqueous media and in absolute ethanol enables to syn-thesis two different morphologies.

3. Line 313 some corrections is there please check it.

• The corrections are made.

4. The photocatalytic dye degradation results should be compared other reported materials.

• In section 3.3, we have reported comparisons with similar oxides and composites based on plasmonic nanoparticles (Au and/or Ag).

5. The author should be carried out catalyst stability and reusability studies.

• Stability and reproducibility studies are carried out as part of this work. As reported in our previous work [https://doi.org/10.1016/j.apsusc.2019.03.269 ; https://doi.org/10.1016/j.jphotochem.2022.114427 ], cycling experiments were also realized on the composite catalyst in order to confirm the AuNPs stability on the oxide. The results show that after all cycle, the relative dye concentration degraded is equal to 91 % that avoid any possible leaching of metal ions during a photocatalytic test and prove the strong bond between gold and oxide surface.

An additional comment were added in the manuscript.

6. Which type of the band gap is appeared in optical properties?

• The optical properties investigation revealed an indirect bandgap transition, according Kubelka–Munk relation. As a function of the bandgap value, we calculated the energy levels of the band structure. This information is included in the article.

7. Subtitle 3.4, the authors includes the blank samples investigation.

• In each case, blank tests without catalysts are carried out systematically. The photolysis rate were reported in the histogram of figure 10a.

8. How did you confirm M-O orientations, if possible please carried out the FTIR study?

• The orientation of M-O bonds can be deduced from XRD and/or Raman analyses. Advanced investigations carried out in previous work [https://doi.org/10.1039/C6RA13500E.], enabled us to identify the different M-O bonds and angles O-M-O/ M-O-M orientations.

In this work, these aspects are not discussed in detail, but rather referred to.

9. Improved to the Figures resolution.

• The resolution of the figures is reworked. All figures are prepared in TIF format with good resolution. If necessary, these figures will be supplied for final editing.

10. Carefully check to the typo and topo graphical errors.

• A careful check is made to correct any typographical errors.

Reviewer 2 Report

In this paper the authors developed dyes degradation under solar light irradiation by using Au/WO₃ composite as photocatalyst. Some interesting results including were obtained in the manuscript. However, there are some questions and unclear statements which must be answered and revised. In my opinion, this manuscript can be suitable for Catalysts after addressing the following issues:

1.     Compared to the reference profile, the intensities of peaks corresponding to (400) and (112) plans are obviously different for NP and PS of WO₃ in figure 1. The authors should explain this.

2.     The nearly same color is used to depict different XRD patterns of (e) Au/WO₃-NP and (f) Au/WO₃-PS in figure 7. The authors may revise the different colors to express the different materials.

3.     In line 352 and 353, Figure 4 shows nitrogen sorption isotherms of WO3-NP and WO₃-PS. However, the isotherms are not display in manuscript. Actually, Figure 4 indicate absorption spectra of the dyes based on UV-Vis analysis using Au/WO₃ NP composite. The authors should be carefully checked and modified.

4.     From line 539 to line 560, the authors detailly discussed the results of nitrogen sorption of WO₃-PS composite, the figure should be provided in manuscript.

5.     The formation of references should be carefully checked and revised according to the regulations of journal.

not applicable

Author Response

Dear reviewer,

I'd like to thank you for reviewing this article, and also thank you for your pertinent and constructive criticism.

1. Compared to the reference profile, the intensities of peaks corresponding to (400) and (112) plans are obviously different for NP and PS of WO₃ in figure 1. The authors should explain this.

• Unlike platelets (high anisotropy), pseudospheres have three equivalent main orientations, thanks to the isotropy of the spheres.

Consequently, orientation (400) is more intense in the case of platelets (orientation corresponding to the large surface) than in PS of WO₃. The same applies to orientation (112).

2. The nearly same color is used to depict different XRD patterns of (e) Au/WO₃-NP and (f) Au/WO₃-PS in figure 7. The authors may revise the different colors to express the different materials.

• XRD figures of materials are reviewed with different colors.

3. In line 352 and 353, Figure 4 shows nitrogen sorption isotherms of WO₃-NP and WO₃-PS. However, the isotherms are not display in manuscript. Actually, Figure 4 indicate absorption spectra of the dyes based on UV-Vis analysis using Au/WO₃ NP composite. The authors should be carefully checked and modified.

• The figure legend is corrected and their numbers adjusted.

4. From line 539 to line 560, the authors detailly discussed the results of nitrogen sorption of WO₃-PS composite, the figure should be provided in manuscript.

• As suggested, the adsorption isotherm figure is added for both catalysts WO3 and Au WO3. ,

5. The formation of references should be carefully checked and revised according to the regulations of journal.

• All references are corrected and adjusted to the journal format using Zotero software.

Reviewer 3 Report

In this research paper, the authors reported a composite from Au/WO₃ for the photocatalytic degradation of dyes, which may help to tackle the aqueous pollutants. I recommend resubmission of this work after addressing the following issues. I will re-evaluate the suitability for publication.  

 

1.      Try to condense the introduction. Now it is too long to be an introduction section and more like a “mini review”. Just include background information, work done by others and motivations of this work.

2.      The numbering of headings is messy.

3.      In line 352: 1) The name “nitrogen adsorption-desorption isotherm” is more commonly used. 2) Where are they? In Figure 4???

4.      Did the authors do replicates for Figure 10? Error bars?

5.      Please also explain why the authors select these three dyes as model pollutants. Do they share similarities with real environmental pollutants?

6.      To tackle the pollutants in aqueous environments, you do not necessarily need to degrade them. It can also be physically absorbed, adsorbed, or recycled. The authors need to discuss this before moving to the chemical degradation method. Cite a recent paper that reported absorption and recycling of pollutants with coacervation 10.1002/smll.202201721.

7.      What the arrow and colored lines mean in Figure 4 is unclear. Please make Figure 4 self-explanary.

8.      Move the (a), (b), …, (f) in Figure 1 to top left position to be consistent.

9.      Make borderlines of individual figures in Figure 3 clear.

Author Response

Dear reviewer,

I'd like to thank you for reviewing this article, and also thank you for your pertinent and constructive criticism.

1. Try to condense the introduction. Now it is too long to be an introduction section and more like a “mini review”. Just include background information, work done by others and motivations of this work.

• The introduction is revised and reduced as suggested by the reviewer. However, it should be noted that another reviewer has asked us to add a discussion with additional references. We try to find a compromise for this part.

 

2. The numbering of headings is messy.

• The title numbering has been corrected.

3. In line 352: 1) The name “nitrogen adsorption-desorption isotherm” is more commonly used. 2) Where are they? In Figure 4 ???

 

• The figure is forgotten, the adsorption-desorption isotherm figure is added,

4. Did the authors do replicates for Figure 10? Error bars?

• Replicats tests were only carried out on MB analyses, as reported in previous work [https://doi.org/10.1016/j.jphotochem.2022.114427]. The error bars is of the order of 5%. However, stability and recyclability tests were carried out on all dyes. The results show that after three cycles, the relative concentration of degraded dye remains quasi-constant (± 3%).

5. Please also explain why the authors select these three dyes as model pollutants. Do they share similarities with real environmental pollutants?

• The composites in our case were obtained using a novel approach, by impregnation/ reduction of gold on WO3 oxide. This initial study enabled us to characterize the catalysts, in particular the composites, and probe their photodegradation capacity under visible light.

In a second phase, we started a study of the photodegradation of antibiotic residues (real pollutants) under solar irradiation. The results obtained are the subject of an article currently in preparation.

6. To tackle the pollutants in aqueous environments, you do not necessarily need to degrade them. It can also be physically absorbed, adsorbed, or recycled. The authors need to discuss this before moving to the chemical degradation method. Cite a recent paper that reported absorption and recycling of pollutants with coacervation 10.1002/smll.202201721.

• Physical processes can be effective in treating aqueous media. Adsorption, absorption and recycling are methods of separating and treating aqueous environments by coacervation, completely different from advanced oxidation processes.

A comment is added in section 3.3, citing the suggested reference;

7. What the arrow and colored lines mean in Figure 4 is unclear. Please make Figure 4 self-explanary.

• The arrows indicate the different spectra measured at each sampling time, from 0 min to 180 min.

8. Move the (a), (b), … , (f) in Figure 1 to top left position to be consistent.

• As suggested, the indexing of the figures has been redone.

9. Make borderlines of individual figures in Figure 3 clear.

• The borderlines of the individual figures in figure 3 are adjusted.

Reviewer 4 Report

Author have investigated on plasmonic photocatalyst based on Au nanoparticles and WO3 for visible light induced photocatalytic activity. The present study seems to be novel & well-documented with clear experimental and discussions in a way that it would be interesting to readers. I would like to recommend that the manuscript can be accepted in its current form for publication.

Author Response

  Dear reviewer,

I'd like to thank you for reviewing this article, and for your consideration of our work.

Best regards

Round 2

Reviewer 3 Report

I suggest acceptance of this work in current form since the authors have addressed my comments.