Reflection Interference Spectroscopy Technology Monitoring the Synthesis of ZnCl2-ZnO Nanosheets on Nanoporous Anodic Alumina Substrate in Real Time
Round 1
Reviewer 1 Report
Dr. Kaige Wang manuscript is devoted to will develop RIfS technology and try to establish a monitoring and analysis model to directly reveal the synthesis process of the nanocomposite films. From previous works, I can note that the guys have developed a fairly simple technology of SERS structures. However, there are many questions:
1. Maintaining, I believe, is a compilation of previous articles by the authors. They were supposed to focus not on the importance and relevance of nanostructures based on chloride, but on the issue of studying the control of the ordering of chloride nanoflakes. What has been done before? How have other authors explored this? Is there a need for such a study? Authors should globally rework introductions.
2. The introduction says nothing about the effect of chlorides on porous alumina. And this is an extremely important issue. Alumina is quite sensitive to acids and alkalis, they dissolve it. The authors should have referred to recent work by Poznyak et al. doi.org/10.3390/coatings10090875 on the dissolution of alumina in various acids. Necessarily.
3. The authors did not pay attention to porous alumina in the experimental part either. However, this is an important issue. They had to show the anodization kinetics or refer to other authors. For example Pligovka et al. doi.org/10.1016/j.matpr.2021.05.263 performed anodizing of porous alumina in oxalic acid solutions where the kinetics are presented in detail. Necessarily.
4. The NpAA-ZnCl2/ZnO construction is misleading. Classically: Zn/Cu describes a two-layer system where a layer of Zn is on top and a layer of Cu is below. In the case of Zn-Cu, Zn is below, Cu is above. Please correct your designation in accordance with these principles.
5. Big question on zinc oxide. I have looked at your previous work but have not found an explanation. Where does zinc oxide come from? You dissolve zinc chloride in water, naturally dried it and you have zinc oxide. This is an important question. Is this the result of interaction with a solvent, with a washer, with porous alumina?
6. Where is the zinc oxide in the film structure? Is its concentration always the same or will it change depending on the conditions of the experiment.
7. Approach bothers me a lot. Authors have built an interferometer. Invented a bicycle. Ok. But why did they do it. I didn't find a clear explanation. Why was it impossible to fix the conditions for the formation of films and strictly adhere to them in order to obtain a reproducible result from time to time? Authors don’t examine the composition of the soup that you cook at home every time you cook? You stick to the recipe and that's it. This is a very important question. Authors should show this more clearly in the introduction so that the reader understands why you reinvented the interferometer.
8. There are also problems in methodology. Authors calculate the thickness from optical density. The optical density depends on the refractive index of the film. But there are questions about this. Firstly, the zinc chloride is nanostructured, in other words, it consists of flakes and the location and composition of these flakes will affect the refractive index, this is the first. The second ratio of chloride and zinc oxide will affect the refractive index. Finally, the parameters of the alumina will affect the interference pattern. And you did not show how chloride affects aluminum oxide. Perhaps the chloride will etch the pores of the alumina and this will change the interference pattern.
9. Explain to me. Why didn't you make a series of samples, choose the optimal shaping mode and stick to it to get structures?
10. No need to repeat key words from the title and introduction.
11. The conclusion should consist of listing the main results on which your main conclusion is built.
12. Figures, abstract and conclusions should be read independently, without reference to the main text. It is not desirable to use abbreviations, or it is desirable to disclose them separately.
13. It is necessary to justify what role the porous alumina plays in your case. Why was this morphology chosen? Why didn't you take glass or silicon? Any other planar substrate?
14. Personal pronouns can't be used in scientific works. Correct lines 132,180,220,221,252,258
15. Sentences should be rewritten according to the style of scientific works and grammar. Line 124,139
1. Personal pronouns can't be used in scientific works. Correct lines 132,180,220,221,252,258
2. Sentences should be rewritten according to the style of scientific works and grammar. Line 124,139
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article presents a potentially useful method for monitoring nanostructured material thickness during synthesis. However, I can not recommend its publication in its present form for the following reasons:
-
The introduction is too general. What is the motivation for use of the specific materials? Physical and mathematical background should be reviewed including transfer-matrix method. It is unlikely that the composite layered system PAA-ZnCl2/ZnO can be described by equation (1) in the article.
-
Section 3.2.1. states that EOT values were calculated through FFT and presents example results in figure 4b. However, the method is not validated, nor are any references given. It is not clear how the peaks in figure 4b were assigned to nanoPAA and film. It could be a simple aliasing effect or other artifact.
-
During ZnCl2/ZnO growth, the EOT value should increase with time, but in figure 4c and 6 it decreases. Why?
-
From section 2.2. one can understand that the spectra were automatically and continuously recorded. This should produce a considerable amount of data points. However, figure 4c and 6 have at most 11 samples. Why so few? The “stage II” as described in text can not really be identified.
-
Precision of pore diameter measurements in fig.2b seems unrealistic.
-
Why units of nm*10⁴ are used for EOT instead of micrometers?
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Manuscript photonics-2349498
Dr. Kaige Wang manuscript is devoted to will develop RIfS technology and try to establish a monitoring and analysis model to directly reveal the synthesis process of the nanocomposite films.
Response 1: The questions are very valuable and important to us. We agree with your opinion.
We have been working on this area since 2015. In our previous series work, we have summarized and reported some of preparation process, growth characteristics and laws of (ZnCl2-ZnO)/NpAA thin films; Meanwhile, we also used this kind of film as the solid substrate of the SERS method, and based on SERS technology, we monitored the ultra-low concentrations of rhodamine 6G, the interaction between single DNA molecule and surfactant molecules; we also explored the superhydrophilic properties of this type composited films, etc.(reference [39][40][43]. However, in practical work, we have encountered some difficulties. We need to timely master the properties such as morphology of the material, thus we need to frequently use SEM to observe the morphology of the thin film, which resulting in a interruption of the continuous growth of the sample, and more, this process is expensive and time-consuming (it is also required to schedule testing time, to wait for testing, etc.). In order to address these issues, the work reported here focuses on finding an effective real-time monitoring method for thin film growth, without the need for expensive and large scale instruments.
Regarding the research on the mechanism of thin film growth and other issues you mentioned, we have conducted in-depth and detailed studies combining theory, simulation, and experiments. Some meaningful results will be reported very soon in the next paper. Of course, we also hope to have an opportunity to send you for review and guidance.
Base on your comments and our careful consideration, we have rewritten the introduction carefully.
R2Q1. The presented material technology aroused my interest in economy and simplicity, if it really works. However, you simply have to provide a photo of your actual thickness control setup in this article. The diagram does not provide a detailed representation.
Response 5: Thank you. We similarly consider it is an important question.
(1) We have detected both ZnCl2 and ZnO during the characterization of the nanosheets, and the TEM result is shown in Figure S1.
Figure S1. High Resolution Transmission Electron Microscope image of ZnCl2-ZnO nanosheets
R2Q2. Oops, did you determine the composition using transmission electron microscopy? I don't think it's correct to write like that. Perhaps it was some other method? Specify.
Response 6: Thank you for the questions which are very valuable and important.
According to the TEM image in Figure S1, zinc chloride and zinc oxide are mixed in the nanosheets.
It has been found that there is no clear boundary between ZnCl2 and ZnO in nanosheets, and it is complicated to accurately calculate their proportion ratio. At present, based on our experimental data, significant differences among these composited thin films synthesized with different concentrations of precursor have not been found. In the future, more experimental data and in-depth analysis are needed, which are we doing now.
R2Q3. You determine the thickness based on the optical density (refractive index of the material). You must be sure that the composition does not change when the application method is changed. Otherwise, your thickness measurements will not be correct. For example, you will change the ratio of the phases of oxide and zinc chloride. How do you solve this issue?
Response 7: Thank for your interesting question. The question is very important. We strongly agree with you that it is indeed necessary to obtain the proper parameters of preparing conditions for the thin films.
Our research on the optical reflection interferometry measurement method is mainly based on the following considerations:
(1) We are trying to produce the film in large quantities, so we need a safe and convenient, low-cost, and non-destructive technology to monitor the film growth in real-time.
(2) It is not only zinc chloride can be used as a precursor to synthesize bilayer nanocomposites, but other metal chlorides also have similar characteristics and can be used as precursors to synthesize new nanosheet composites. However, there are some differences between the structure, morphology, synthesis time, etc. We need to understand and master these differences in a timely manner.
(3) Based on your suggestion and careful consideration, we have added some content in the introduction in this version; please see lines 47-54, page 2.
R2Q4: Please add a photo of your setup to the manuscript. It will be useful and will remove a number of questions. In addition, it will be of great value to those readers who can use your method and come back to reproduce the installation for themselves.
Response 10: Thank you for your value comments. We have modified the keywords as follows:
Keywords: reflection interference spectroscopy; effective optical thickness; self-assembly; composite film; non-destructive monitoring.
R2Q5: You repeat words from titles and abstract again. Come up with something new, no need to repeat. This will increase the views of your article.
By the way check it out. I'm not sure if the “reflection” is correct, probably better “reflectance”.
Response 11: Thank you very much for pointing out this.
We have made global changes to the conclusions in this version.
R2Q6: It is better to do this according to paragraphs 1. 2. 3 ......
Response 13: Thank you for your valuable comments. we have added corresponding content in the introduction.
It is well known that nanoporous anodic alumina (NpAA) is a good template for preparing nanostructures. NpAA has a controlled structure, and stable physical and chemical properties. NpAA does not react with lower concentration zinc chloride solution, and easily is peeled out from the bottom aluminum metal. Besides, we have tried to produce nanosheets on the surface of silicon wafers; unfortunately, we could not form nanosheet structures but caked up.
Based on your comments, we have added corresponding content in the introduction, please see line 69, page 2.
R2Q7:
Please specify in the manuscript more clearly. Is it possible to form your structures on cheaper planar plates (glass, sital, silicon, etc.) and why such a pore diameter and oxide cell size and thickness were chosen.
R2Q8: Please improve the layout of the figs so that all figs look the same across the width of the page. For example, Fig 1 is centered, Fig 2 is not. You place the fig vertically, when there is a lot of space on the right and left. What is it for? Fig 6 on the right and left, leave free space. Tidy up all the drawings so that the article is pleasant to read, pay attention to the little things.
Authors need to learn how to use the "Review" mode in Word in order to see their changes in detail.
Comments for author File: Comments.docx
I did not notice any gross errors, but it can be improved in terms of style.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 2 Report
Authors have successfully addressed most of concerns. However, the number of data points in fig 4c and fig 6 is still not sufficient.
Author Response
Please see the attachment
Author Response File: Author Response.docx
