Iridescence and Luminescence from Opal Matrices for Show Business

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this work, inexpensive opal matrices enable the creation of beautiful multicolor images using a simple setup. Their inherent iridescence is enhanced when immersed in ethanol. And the upconversion luminescence from Er³⁺ and Yb³⁺ ions in the xerogel/opal structure adds an additional color dimension to the iridescent display. Hence, this paper could be published in the Photonics after thinking over the following points for improvements.

 1. Why was upconversion luminescence not observed in sample 3 after annealing at 450 ℃ for 30 min, while sample 4 did after annealing at 600 ℃ for 30 min? A more detailed discussion is needed here, or more effective evidence should be provided. (For example, the variation of XRD pattern)

2. In the introduction part, it mentioned that “opal matrices can exhibit iridescence in liquids”. So, why use ethanol to improve the iridescence of opaque opal substrates instead of other solutions. It is well known that ethanol is volatile, which will limit its practical application prospects

Author Response

Author’s response to the Reviewer #1.

The authors are grateful to the Reviewer for careful reading of the manuscript and useful comments. Please find the attached Reply

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article is presenting in a clear and well addressed manner how the use of opal matrices in different environments (ethanol or doped luminescent xerogels), can contribute towards obtaining attractive images or videos for show industry. The article is well written and is highly relevant with the scope of the special issue of the Photonics journal and I suggest the acceptance with minor revisions.

On the introduction, the references are appropriate, however, I would suggest using some more recent ones if possible.

On the materials and methods, I suggest some improvements in English section for rephrasing

On the results and discussion:

• Figures. The scale bars are missing. In Figure 1 legend there is no information about the sample size. I would highly suggest to use scale bar in the pictures. If possible, it would be nice to have the colorbars to show the luminosity scale of the samples.
• Figure 2. The sample seems to be completely impregnated in ethanol as stated by the authors. The difference between the images a to e is not clearly stated on the figure legend or the text. 
• The time scale information-if applicable is missing for Figures 1 and 2.
• The Figure 3 information is described adequately, however I would still use a scalebar in the images.

On the conclusions:

• Sentence 149, the price of the opal matrices or the competitor materials is not discussed on the article. If the authors want to mention it, I would suggest to justify it before.
• Even though it is shortly discussed at sentence 159, how the opal matrices could be used, I would suggest the authors to give specific application examples of them to the show business, if possible, as this is the focus of this article.

Comments on the Quality of English Language

Overall the quality of English language is good. The following comments are mostly focused on the formality of the language for a scientific journal.

Specifically,

1.  The abstract is written informally and does not reflect the academic language expected in a scientific publication. For example in the sentence 18 the word 'beautiful' can be replaced from the words 'visually appealing/attractive'. On the same way I would suggest to modify the sentence 23 accordingly.
2.   In the materials and methods section, the sentences 48-50 need to be rephrased to state, firstly the purpose or objective of the experiment, followed by a description of how it was implemented, in the specific case the four sample preparation. Additionally, I would avoid referring to the author who produced the sample by name in the main text, as scientific writing typically maintains an impersonal tone. The contribution should be declared on the author contributions section, as it is already stated.
3. In the results and discussion I would recommend a passive voice as more formal tone. However, If the authors prefer the active voice, it is also acceptable if it remains consistent throughout.

Author Response

Author’s response to the Reviewer #2.

The authors are grateful to the Reviewer for careful reading of the manuscript and useful comments. Please find the attached Reply.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript titled “Iridescence and luminescence from opal matrices for show business” reports the synthesis of opal matrices impregnated with BaTiO₃ xerogels doped with Er³⁺ and Yb³⁺ ions, demonstrating the combined effects of iridescence and upconversion luminescence. The authors present optical experiments under white light and 980 nm laser excitation, showing that ethanol impregnation enhances iridescence and that heat treatment at 600 °C enables simultaneous observation of both effects. The study suggests potential applications in visual displays and decorative optics.

The work is interesting, and the approach is promising; however, the manuscript requires substantial improvement in data presentation, clarity, and scientific rigor before it is considered for publication in Photonics.

1. The abstract should be rewritten to emphasize scientific objectives, methods, key quantitative results, and applications, while removing informal and vague statements.
2. Scientific novelty is not clearly articulated. The authors must clarify the specific advancements over previous studies and cite recent related works to strengthen the context.
3. The rationale for ethanol impregnation and its detailed effect on optical properties require further explanation.
4. Figure corrections are required, and the labels in Figure 3 should be fixed, as (g) is repeated, and Figures 5(a) and 7 should use the direct labels “with ethanol” and “without ethanol” instead of numerical codes.
5. Yb³⁺–Er³⁺ mechanism is only briefly mentioned. The manuscript should provide an appropriate energy-level diagram, a clear mechanistic explanation, and quantitative data to substantiate the role of these ions in luminescence enhancement.
6. Data presentation relies mainly on qualitative images. Quantitative optical data, such as PL intensity comparisons, spectral shifts, and transmission/reflection spectra for all samples (#1–#4), are necessary to support the conclusions.
7. Material stability under repeated ethanol impregnation, laser irradiation, and thermal cycling is not discussed. Experimental evidence or references should be included to assess the long-term reliability.
8. Language and style require thorough proofreading to eliminate informal expressions, grammatical errors, and inconsistent terminology, ensuring a formal scientific tone throughout.
9. References should include more recent and relevant studies to enhance the scope and readability.

Author Response

Author’s response to the Reviewer #3.

The authors are grateful to the Reviewer for careful reading of the manuscript and useful comments. Please find the attached reply.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

All the questions were well replied. The current revision can be accepted for publication in Photonics.

Reviewer 3 Report

Comments and Suggestions for Authors

The revised version of the article shows significant improvement over the previous submission. All previously raised concerns have been thoroughly addressed or satisfactorily explained. I recommend acceptance for publication without further revisions.