Aqueous Precipitate of Methanolic Extract of Bergenia ciliata Leaves Demonstrate Photoirradiation-Mediated Dual Property of Inhibition and Enhancement of Silver Nanoparticles Synthesis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work explores green synthesis of silver nanoparticles using two sub-fractions of a methanolic Bergenia ciliata leaf extract (PME, DME) under dark and white-light conditions. The authors quantify phenolics and FRAP, characterize phytochemicals by GC–MS, and assess AgNP formation kinetics, size (DLS), morphology (SEM), composition (EDX), and 15‑day stability. DME reduces Ag+ efficiently in the dark, while PME is inhibitory in the dark but promotes AgNP formation in light and modulates AE-based synthesis. Pyrogallol is proposed as the main reducer, with PME fatty acid esters implicated in a light-dependent inhibitory/switch behavior.

Minor comments:

1. The authors should improve consistency and clarity in terminology and abbreviations, e.g., standardize “photoirradiation” vs “light exposure”, define “825 lumens” more precisely (intensity and spectral distribution), and ensure all abbreviations are defined at first use in the main text, not only in the list.
   2. The authors should revise figure and table captions to be more self-contained, explicitly stating sample type, light condition, number of replicates, and error bar meaning (e.g., mean ± SD, n), and ensure that axis labels include units.
   3. The authors should carefully proofread for minor language issues (e.g., missing articles, awkward phrases such as “convert enhance the NP synthesis”) and harmonize the tense and style across Abstract, Results, and Conclusions.

Major comments:

1. The mechanistic interpretation that fatty acid esters in PME act as light-sensitive inhibitors of AgNP synthesis in the dark and are “photodegraded or isomerized” under light is largely speculative; the manuscript should either provide direct experimental evidence (e.g., time-resolved GC–MS under illumination, additional control extracts) or clearly frame these points as hypotheses and substantially soften the causal language.
   2. Quantitative and statistical treatment of the data is insufficient: the manuscript reports means and some standard deviations but does not clearly state the number of independent experiments, the statistical tests applied, or significance thresholds; a proper statistical analysis (including indication of significant differences in tables/figures) is needed to support key claims about “significant” changes in size, composition, and synthesis rate. When it comes to the DLS, the authors should indicate which angles were used during the measurements? SEM images according to the scale are showing particles of approx. 100 nm in diameter whereas DLS gives values 4 to 5 times smaller (even with a very big PDI). What is the explanation for that?
   3. The work repeatedly refers to previous AE/ME studies to motivate the design and interpret outcomes, but the current manuscript should more clearly delineate what is genuinely novel (e.g., specific mechanistic insights from PME/DME separation) and reduce descriptive repetition; strengthening the comparison with earlier data and adding a concise schematic or table highlighting the new contributions would improve the scientific impact and focus.
   4. The structure of the abstract should be revised. Abstract should be narrative and not directly divided into the sections like methods, results and conclusions. 
   5. The title should be revised and the authors may consider something more compact and more clear. 

Comments on the Quality of English Language

English is generally understandable and acceptable for publication, but the manuscript would benefit from careful language editing to correct numerous minor issues (articles, plurals, verb tenses, word repetition) and to improve clarity and concision in the Introduction and Discussion.

Author Response

Comment 1: This work explores green synthesis of silver nanoparticles using two sub-fractions of a methanolic Bergenia ciliata leaf extract (PME, DME) under dark and white-light conditions. The authors quantify phenolics and FRAP, characterize phytochemicals by GC–MS, and assess AgNP formation kinetics, size (DLS), morphology (SEM), composition (EDX), and 15‑day stability. DME reduces Ag+ efficiently in the dark, while PME is inhibitory in the dark but promotes AgNP formation in light and modulates AE-based synthesis. Pyrogallol is proposed as the main reducer, with PME fatty acid esters implicated in a light-dependent inhibitory/switch behavior.

Response 1: We thank the reviewer for agreeing to review the manuscript, and giving us an opportunity to respond to the queries as raised. We also thank the reviewer for the queries raised, as it has indeed helped us get a better insight of our manuscript, and added some clarity to the objective of the manuscript. We have carefully analysed every major and minor query, and tried to respond in the best possible way. We have also modified the manuscript significantly as suggested by the reviewer.

Comment 2: The authors should improve consistency and clarity in terminology and abbreviations, e.g., standardize “photoirradiation” vs “light exposure”, define “825 lumens” more precisely (intensity and spectral distribution), and ensure all abbreviations are defined at first use in the main text, not only in the list. 

Response 2: Our sincere apologies for the inconvenience caused, we have now rectified the errors as highlighted by the reviewer.

Comment 3: The authors should revise figure and table captions to be more self-contained, explicitly stating sample type, light condition, number of replicates, and error bar meaning (e.g., mean ± SD, n), and ensure that axis labels include units. 

Response 3: The figures and table captions have been modified.

Comment 4: The authors should carefully proofread for minor language issues (e.g., missing articles, awkward phrases such as “convert enhance the NP synthesis”) and harmonize the tense and style across Abstract, Results, and Conclusions. 

Response 4: Our apologies for the grammatical errors, and lack of coherent sentences. As suggested by the reviewer, we have now reedited the manuscript thoroughly to address the language issue.

Comment 5: The mechanistic interpretation that fatty acid esters in PME act as light-sensitive inhibitors of AgNP synthesis in the dark and are “photodegraded or isomerized” under light is largely speculative; the manuscript should either provide direct experimental evidence (e.g., time-resolved GC–MS under illumination, additional control extracts) or clearly frame these points as hypotheses and substantially soften the causal language. 

Response 5: We thank the reviewer for a very insightful suggestion. Indeed, the mechanistic interpretation was very difficult for us, and we could only think of fatty acid, specifically palmitic acid (PubChem ID: 985) as a probable player because of its abundance in PME, which is only second to pyrogallol. Yet, we were aware that the assumption lacks any evidence, hence, it may be an exaggeration, as rightly pointed by the reviewer. In response to that, we did further literature research for evidence using keywords “effect of photoirradiation on palmitic acid”. We found two major citations which could support our hypothesis of palmitic acid being the inhibitor of AgNP synthesis as it can undergo degradation on photoirradiation. In the revised manuscript we have modified the sentence to convey our interpretation.

Comment 6: Quantitative and statistical treatment of the data is insufficient: the manuscript reports means and some standard deviations but does not clearly state the number of independent experiments, the statistical tests applied, or significance thresholds; a proper statistical analysis (including indication of significant differences in tables/figures) is needed to support key claims about “significant” changes in size, composition, and synthesis rate. When it comes to the DLS, the authors should indicate which angles were used during the measurements? SEM images according to the scale are showing particles of approx. 100 nm in diameter whereas DLS gives values 4 to 5 times smaller (even with a very big PDI). What is the explanation for that?

Response 6: 

With regards to the statistical analysis, we have added a paragraph in the methodology on statistical analysis. All experiments were performed in triplicates, and three independent experiments were performed for each methodology. P-values threshold has been added in the revised figures and their captions. Furthermore, we would like to humbly draw the attention of the reviewer to the caption of figure 8, wherein p-values should be >0.05, since it is a stability study. Any change in p-value <0.05 in declining pattern would mean that the nanoparticles are not stable.

The DLS angle was set to a default setting of 90° angle. We have now added the information in the methodology of the revised manuscript.

With regards to particle size analysis by DLS and SEM, we credit the difference in particle size measurement to the sample population, and sample preparation process for analysis. In SEM, only few hundred or a thousand particles can be analysed, whereas, in DLS, millions of particles are analysed at the same time. Furthermore, in DLS, the particles are homogeneously distributed as confirmed by the PDI, and remain in colloidal suspension throughout the analysis period. On the contrary, in SEM, the particles are dried in a desiccator before analysis can be done, in the process, the particles tend to get agglomerated as the water molecules are evaporated, hence the tiny particles tend to get agglomerated resulting in large lumps, leaving only few of the larger nanoparticles which did not agglomerate. Hence, we relied more on DLS for sample size distribution, and SEM was used for asserting the morphology of the nanoparticles rather than size distribution. 

Comment 7: The work repeatedly refers to previous AE/ME studies to motivate the design and interpret outcomes, but the current manuscript should more clearly delineate what is genuinely novel (e.g., specific mechanistic insights from PME/DME separation) and reduce descriptive repetition; strengthening the comparison with earlier data and adding a concise schematic or table highlighting the new contributions would improve the scientific impact and focus. 

Response 7: We agree that the manuscript needs avoid repeatedly referring to previous AE/ME studies, hence we have modified the sentences, and focused entirely on PME/DME, except when necessary, referencing is required. Our intent was always to present the current work entirely as a novel one, and we would like to draw the reviewer’s attention to figure 9 and 10, wherein we tried to present a schematic representation of our findings, and their possible interpretation in the discussion section.

Comment 8: The structure of the abstract should be revised. Abstract should be narrative and not directly divided into the sections like methods, results and conclusions. 

Response 8: As suggested by the reviewer, we have edited the abstract.

Comment 9: The title should be revised, and the authors may consider something compact and clear. 

Response 9: We thank the reviewer for giving us a light by using the term “photosensitive inhibitor of nanoparticles synthesis.” We have now revised the title of the manuscript with more clarity. 

Reviewer 2 Report

Comments and Suggestions for Authors

 

   

Comments for author File: Comments.pdf

Author Response

Comment 1: The article aligns well with the journal’s scope, as it reports the synthesis of colloidal AgNPs using the methanolic extract of Bergenia ciliata. The article's structure is logical. Relevant and clear tables were provided in the manuscript. The conclusions are consistent with what was presented in the manuscript. However, several aspects require clarification and improvement before publication to enhance its scholarly contribution.

Response 1: We are thankful to the reviewer for agreeing to review the manuscript. With regards to the critical points raised by the reviewer, we have tried our best to respond to each query pointwise, and include the necessary changes. We are convinced that the reviewer has only given constructive suggestions that has helped us in improvising the manuscript.

Comment 2: The title should be modified as it's not clear. Initially, I thought the inhibition properties of AgNPs were being investigated. 

Response 2: The title has been significantly modified to summarize the objectives of the study.

Comment 3: The introduction should be improved as there are state-of-the-art reports on your topic. The references did not include any 2025 papers. 

Response 3: We thank the reviewer for the suggestion of improvising the introduction. The introduction has been thoroughly revised to address the research domain.

Comment 4: If you compare Figure 3 with Figures 2, 4, and 5, you will observe that the font sizes of the exes are smaller and difficult to read. 

Response 4: We thank the reviewer for pointing the difference, we have now edited the font size.

Comment 5: Based on the outcomes of this work, which extract should be chosen if a smaller size and higher yield of the AgNPs are required? This is because certain applications are affected by the size of nanoparticles. 

Response 5: We understand the reviewer’s curiosity of the particles size influence on the application of the nanoparticles. Indeed, the particles size enormously influences the application, and in several cases, smaller size preferably has better application efficacy. In this case of silver nanoparticles, PME-based silver nanoparticles are considerably smaller than DME-based silver nanoparticles. However, photoirradiation results in increased particle size in both PME and DME. On the other hand, PME significantly diminishes the particle size of AE-based silver nanoparticles, both in dark and light conditions. Thus, suggesting that PME is preferable over DME when it comes to controlling nanoparticles size.

Comment 6: The authors should provide other literature precedents where plant extracts show such dual properties in the synthesis of metallic nanoparticles. How does this specific combination of plant extract and photo-irradiation method compare to similar methods published in the literature in terms of synthesis time, particle size control, yield, and stability? The authors must clearly articulate their unique contribution. 

Response 6: We agree with the reviewer’s observation that almost every type of research is based on precedents that becomes the foundation of our work. However, our extensive literature search failed to find a single research article which reported the dual property of enhancement and inhibition of nanoparticles synthesis. In fact, we too never anticipated a contrasting outcome of photoirradiation on nanoparticles synthesis. Every source of extract has its unique phytochemical composition, and furthermore, the process of extract preparation also varies. In this regard, Bergenia ciliata leaves till date were not explored for silver nanoparticles synthesis. With all responsibility, we can attest that our study is the first of its kind report, wherein an external factor could significantly modulate the outcome of nanoparticles synthesis.

Likewise, we do agree with the second observation made by the reviewer, that similar research could be cited in our manuscript wherein photoirradiation influences the particle size, nanoparticles yield, and stability. However, they are very few studies that have been published. Hence, in the current study, we have added the latest and only citations that we could come across in literature search, in the introduction part. This will a perspective to the readers about the context of the manuscript. Furthermore, this also addresses the 2^nd query that was raised by the reviewer.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I am both surprised and concerned by the limited number of references. Research published in international journals must be based on the latest, relevant literature. I appreciate the significant improvements to the manuscript, but without further revisions, it can only be considered a scientific report.

Comments on the Quality of English Language

English is generally understandable and acceptable for publication.

Author Response

Comment 1: I am both surprised and concerned by the limited number of references. Research published in international journals must be based on the latest, relevant literature. I appreciate the significant improvements to the manuscript, but without further revisions, it can only be considered a scientific report.

Response 1: We understand the concern of the reviewer about the limited number of references. However, we would like to assure the reviewer that we have referred to sufficient citations as was required for introduction and conveying the interpretation and corroborations of the research findings. In fact, in the revised manuscript, we have replaced three irrelevant references, with nine new references from 2023-2026. Overall, as suggested by the reviewer, we have now raised the number of citations from 17 to 22. Furthermore, there are very limited reports till date about photoirradiation-based green synthesis of silver nanoparticles, much less on dual-property of photoirradiation on nanoparticles synthesis. Hence, we are unable to find specific references that may be necessary for citations. 

In the revised manuscript, our only reference that is old is from 1997 which is the only reference which reports on specific outcome that we are looking for. Rest all other citations are from 2015 and above, with majority being from post-2020. 

Reviewer 2 Report

Comments and Suggestions for Authors

I recommend accepting it.

Author Response

Thank you for the acceptance.