Application of Biobased Substances in the Synthesis of Nanostructured Magnetic Core-Shell Materials

Round 1

Reviewer 1 Report

The article on ¨Application of biobased substances in the synthesis of  nanostructured magnetic core-shell materials¨ is well written with enough results and discussions. However, I would like to suggest a few things before its acceptance for publication in Inorganics. The manuscript may be considered for publication once the authors have done the necessary corrections.

1. The similarity index is high, from the single source also high and coinciding with the previously published articles from the same group. Hence I request to reduce the similarity index of this manuscript.

2. The particle size reduction is clearly vision from the TEM micrograph with the increasing BBS. The author may include the particle size distribution curve for the TEM micrograph to understand the size distribution intensity as well the shift in the size distribution with the addition of BBS.

3. With increasing BBS concentration the metal-oxide bond width in the FTIR is increasing or changes. Can the author include the discussion of cation distribution or the site information with the structure of Fe3O4. The authors may refer to the following reports, https://doi.org/10.1016/j.apsusc.2019.04.177 and DOI 10.1088/2053-1591/ab24e8

4. In figure 3B, the authors may include the coercivity as a double y-axis graph to understand the variation with coercivity also. It is surprising that the coercivity also decreases along with the saturation magnetization with an increasing fraction of BBS. The decrease in the saturation magnetization may be due to the non-magnetic fraction as well as the reduction of particle size. However, with the decrease in the particle size ranging from 200 nm to 5 nm, we could not find the increasing trend of coercivity as the size decreases (approaching a single domain regime).  It will be good if the author includes the discussion on superparamagnetic size and single domain size. The author may refer to the following article for the discussions, https://doi.org/10.1016/j.jpcs.2013.07.005

5. in line 168, the authors write as ¨The XRD pattern of MBBS@mSiO2 (Figure 5A) confirms  Fe3O4 or -Fe2O3 as the main crystalline phases, indicating that the IONPs did not undergo any crystalline transformation during the mSiO2 synthesis step and their subsequent calcination. ¨ Author should clearly analyze the data and confirm the phase of the materials. Or indicate both phases are present in the sample.

6. For MBBS@TiO2 sample, If the hematite is forming at 500 C, why the authors have done the calcination at a higher temperature? Is the formation of hematite can get eliminated if the authors have done the calcination at lower temperatures? As there is a two-phase, the reduction in the saturation magnetization may be due to the secondary phase along with the non-magnetic fraction.

7. Author should clearly mention the particle size of Fe3O4 and TiO2 in MBBS@TiO2 system.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The authors synthesized bio based materials coated MNP and by using this material and metal oxide precursors, core/shell structures were prepared through sol-gel and calcination process. The authors showed some applications of these core/shell structures such as drug carrier and catalyst. Actually, these kinds of structure have been introduced from lots of groups and it is hard to find something new, potential and novelty from the article. Thus, this manuscript is not suitable for publication in Inorganics

Additional comments have been followed;

1.      What is the role of bio based substance (BBS) in this study? It is not clear. It seems MNPs could be stabilized by carboxylic group of sodium acetate, and according to the TEM image, they were well dispersed without BBS. However, by adding the BBS, MNP was aggregated and MNP clusters were created. Even, the shape of cluster was not controlled and randomly aggregated. So, it is hard to find the benefit or advantage of BBS in this study.

 If the authors want to claim the stability or homogeneous were improved by BBS, please show the control results by using some polymers like PEG, PLGA and so on to prove that.

 Maybe the biocompatibility or bioactive of BBS coated MNP could be improved due to properties of BBS. However, in this study, such BBS coated MNP was again covered by metal oxide layer for the application including DDS or photo catalytic effect. It meant coating effect of BBS is more blurred because BBS couldn’t act any roles in the metal oxide layer.

 In addition, actually, without BBS, tons of MNP based core/shell structures were already published and introduced in a lot of fields, and they showed excellent application and potential compare with this study. So, it is hard find the novelty of this study.

2.      The authors mentioned that the size of BBS coated MNP in the MBBS-35 case was about 70 ~ 200 nm. It means the size variation of BBS coated MNP is very large and size couldn’t be controlled by method in this study. So, please find optimal condition to prepare the monodispersed particles.

 In addition, please show the DLS and zeta-potential result to prove the size and stability of BBS coated MNP.

3.      Please show the FT-IR spectrum of BBS to compare the BBS coated MNP. And please explain why Fe-O vibration band was broadened after BBS coating. Without BBS coating Fe-O vibration was clearly observed but by increased the BBS concentration, Fe-O vibration band was changed. So, please discuss and explain this part.

4.      The authors prepared the mesoporous structure through calcination process. It meant that not only CTAB but also BBS could be removed by high temperature and as a results, the porosity of BBS coated MNP showed different properties and could be tuned depending on the concentration of BBS. So, please discuss this point based on the BET or other results.

5.      The authors showed TEM images of TiO2 coated MNP in figure 6. However, it is hard to observe the core/shell structure like MNP@SiO2 in figure 4. It seems that MNP was located in the shell structure. So, please show EDS mapping result to identify the core and shell structure.

6.      The authors mentioned that DLC was about 13 %. But there is no related result. So, please provide HPLC result or UV/Vis result to prove it. Also, what is the pH condition for the drug releasing test? Depending on the pH, its releasing behavior might be different, so the target pH value should be considered because of the target organ or conditions.

7.      The authors showed photocatalytic activities of MNP@TiO2 and compared that result with bare TiO2. But it is difficult to observe the enhanced catalytic activity of MNP@TiO2 and its reactivity was not great and linear response. Rather it seems that reactivity of TiO2 was better according to the result. Furthermore, standard deviation was not shown in the graph. Thus it was recognized that the catalytic activity of MNP@TiO2 was not good than that of bare TiO2.

Author Response

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Reviewer 3 Report

The paper presents a novel procedure for the synthesis of core-shell magnetic nanostructures stabilized with bio-based substances. The authors describe the experimantal details concerning the optimization of the synthesis parameters, the characterization of the samples and also the testing of potential applications of the magnetic nanostructures as drug loading carrier and as adsorbents for the quantitative removal of methylene blue.

I consider this paper is a valuable material for researchers working in the field of nanomaterials because it presents a novel green synthesis route to obtain nanostructured materials with controlled properties.

I recommend the publication.

Author Response

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Reviewer 4 Report

I have carefully reviewed the manuscript entitled “”. The manuscript lacks some key information’s and requires extensive revision before consideration for the publication. My comments on the manuscript are below:

1.       The aim of the manuscript is not clear to me as what authors wants to achieve. The use of the biobased substance is generally does to tune the morphology or make the sample more biocompatible.

2.       The authors have used polyol method which is very common and nothing new and ever looking at the quality of the samples, it’s not great. The authors should clear their motivation in the manuscript what they want to achieve.

3.       The size distribution of the samples looks very wide which is not good for any applications. It shows that the authors have no control over the synthesis process making it inappropriate from the application point of view.

4.       The authors written in the Introduction that the Fe3O4 is biocompatible which is not entirely true and highly dependent on the synthesis method and size range. The toxicity associated with this materials is under scrutiny as for clinical applications, the haemolysis rate should be below 5%.

5.       The XRD results are not well analysed. The authors are suggested to present a detailed analysis like crystallite size, dislocation density etc. The authors can follow these papers for the study, Journal of Materials Chemistry C 10 (35), 12652-12679, Journal of Alloys and Compounds 904, 163992, Nanomaterials 11 (11), 3009.

6.       I suggest authors to move the synthesis section above as it is the main part of the paper and it does not make sense to keep it in last.

7.       In the Introduction section, I suggest the authors to add a broader context of the area. There are several new applications of magnetic nanoparticles/ Nanomagnetic fluids such as Temperature sensor, heat exchanger, Drug delivery, magnetic actuators, energy harvester have been reported. I recommend authors to add few lines so that the readers can understand the context. Ex; Sustainable Energy Technologies and Assessments 52, 102024/48, 101641, Applied Energy 239, 1524-1535, IEEE Sensors Journal 17 (9), 2670-2675.  

8.       The results in the application section looks unreliable and authors should also need to add the UV spectra at different times.

9.       The Figure captions are very poorly written. The authors should write the Figure caption in detail. The Figure caption itself be self-descriptive so that it should deliver a clear massage.

If authors can modify the manuscript according to my comments, I would be happy to reconsider the manuscript for publications.

Author Response

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Round 2

Reviewer 2 Report

Thanks for authors' efforts to revise the manuscript and I agree to accept this article for publication in Inorganics.

Author Response

We appreciate the comments of the reviewer

Reviewer 4 Report

Some of the comments on the XRD section of the manuscript have been addressed by the authors, but the section still appears weak. The authors' statement in the revised manuscript that "XRD is not a suitable technique to distinguish between magnetite and maghemite because the XRD patterns of both phases are very similar" is not accurate. It is suggested that the authors carefully review the articles "Journal of Materials Chemistry C 10 (35), 12652-12679, Journal of Alloys and Compounds 904, 163992, Nanomaterials 11 (11), 3009" and revise the XRD section accordingly before any recommendations are made. It appears that the authors have drawn conclusions based on papers that do not have proper analysis of the XRD results. It should be noted that the strong correlation between structural and magnetic properties can be used to differentiate between magnetite and maghemite. By examining the XRD and VSM plots, it is possible to determine the phase of the materials. It is not accurate to simply claim that XRD cannot differentiate between the phases, as it is a highly effective tool.

I also have issues with the reply to my comments 1 and 9. I suggest authors to rewrite other Figure captions as well. Also, Please address the response to my comment 1 and add this details in the manuscript as well.

Author Response

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Round 3

Reviewer 4 Report

The manuscript can be accepted as authors have answered all my queries.