Thin Film Coatings from Aqueous Dispersion of Graphene-Based Nanocarbon and Its Hybrids with Metal Nanoparticles

Round 1

Reviewer 1 Report

Language needs to be improved, e.g., in the abstract: “with easily released structural components for studies under laser.” It is just an example. There are several like that.

Figures are not marked, legends are not visible. Please draw the figure clearly showing the peak position and any shift etc.

SEM image showing charging behavior. These need to be replaced.

Please provide some more proof, like HRTEM, etc.

Particle size distribution should be shown using HRTEM and also plot a histogram.

Author Response

We would like to express our gratitude to reviewers for reading the manuscript and for their comments. All the corrections have been made in accordance with their comments.

Language needs to be improved, e.g., in the abstract: “with easily released structural components for studies under laser.” It is just an example. There are several like that.

• The text of the manuscript was corrected.

Figures are not marked, legends are not visible. Please draw the figure clearly showing the peak position and any shift etc.

The figures were improved:

Fig. 1 – is newly made.

Fig2. – Histograms and TEM images on Ag-ShC hybrid were added.

A table 1 with comparative data on average peaks position was added.

Fig.3 was submitted.

Fig.4,5 legends were improved.

SEM image showing charging behavior. These need to be replaced.

Fig.6. The images are presenting morphology of the films surface and allow us to characterize changes in shape and size of the aggregates under laser irradiation. TEM was carried out in the second electrons regime. The surface of films is not charged. The images were replaced by the ones with lower magnification.

Please provide some more proof, like HRTEM, etc.

Particle size distribution should be shown using HRTEM and also plot a histogram.

 Histograms of ShC and its hybrids under nanosec laser irradiation are presented in Fig.2. TEM images of the film of ShC-Ag hybrid are shown.

Reviewer 2 Report

This paper reported the fabrication of thin film coatings from aqueous dispersion of graphene-based particles and its hybrids with Au and Ag. The topic does not clearly reflect the results obtained, since only a small part of the results is devoted to the formation and characterization of the film. Unfortunately, the results were not adequately presented and discussed. A lot of mistakes and inaccuracies, as well as poorly reported data not allow to evaluate idea of this work. I considered that the paper is not suitable for publication based on the following consideration:

• The photos from Figure 1 are of poor quality. In my opinion, photos should be taken from a greater distance. At the moment, there is no way to properly compare samples with each other. The description of Figure 1 should be changed. It is too difficult to understand the real sample composition and preparation conditions. Moreover, Figure 1 is mentioned in manuscript as a reference to the stability of solutions. In my opinion, it is not possible to specify stability of solutions from such photos. Changes of other parameters such as color or turbidity of the samples should be more discussed in text. In other way, I think that the Figure 1 should be replaced from manuscript.
• The graphs in Figure 2 should be added not as a print screen from program that was used for DLS measurements. Please, add all graphs in the same format throughout the manuscript. The text, which describing Figure 2, does not reflect the information provided in figure:

Lines 159-161: “The average diameter of ShC nanoparticles increases from 100 nm to 291.1 ± 6.4 nm under CW laser exposure and to 703.8 ± 8.9 nm under ns pulse. The most significant changes in the average size of nanoparticles were found under fs exposure: the particle size distribution pattern shows a shoulder in the range of 25–50 nm and a main peak at 500 nm.” It is clear that in case of CW laser the size increase more. However, other information is provided in text.

Moreover, the bimodal size distribution is mentioned in text. However, in my opinion the data from Figure 2 (a and b) shows that such statement is not true enough. If the peak of bigger particles on the graph of the distribution by intensity is high enough and quite low on the graph of distribution by volume, it means that probably the concentration of such particles is quite low. In such case, the distribution by number should be checked one more time. Also, the other techniques could be applied for size measurements. Also, the peak about few nm of (1) sample on Figure 1A does not clarify particle sizes and requires further explanation.

In summary, the Figure 2 should be changes. Description of this figure should be revised. Moreover, additional data in form of graph or table should be added. It also should be noted, that just the distribution by intensity (as opposed to distribution by volume and number) shows the hydrodynamic radius of particles.

• Lines 190-191: “Two broad peaks for ShC–Ag hybrid nanoparticles at frequencies 268, 391 nm, while for ShC–Au at 267, 522 nm, are observed”. It is not frequencies. Please, change to wavelengths or similar. The second peak of ShC-Au presents not at 391 nm.
• Lines 195-197: “The peaks 522 nm for Au and 415 nm for Ag, typical of the nanoparticles of these metals in water are observed.”. In my opinion, λ_max are not typical for Au and Ag nanoparticles in water, but for such nanoparticles of certain size.
• Lines 198-202: Please, add reference confirming this information.
• Lines 204-208: “Under nanosecond exposure, the peak characteristic of ShC shifted to the short-wavelength side 249 nm for Au and to 261 nm for Ag. In the visible region, more significant changes were observed. For the dispersion containing Au it is 526 nm and 406 nm for the dispersion with Ag nanoparticles. It can be assumed that the difference between two dispersions is due to the oxidation of silver particles.” Please provide more information which difference and how can be explained by oxidation of Ag particles.
• Other parts of manuscript should be also additionally revised.

Author Response

We would like to express our gratitude to reviewers for reading the manuscript and for their comments.

This paper reported the fabrication of thin film coatings from aqueous dispersion of graphene-based particles and its hybrids with Au and Ag. The topic does not clearly reflect the results obtained, since only a small part of the results is devoted to the formation and characterization of the film. Unfortunately, the results were not adequately presented and discussed. A lot of mistakes and inaccuracies, as well as poorly reported data not allow to evaluate idea of this work. I considered that the paper is not suitable for publication based on the following consideration:

• The photos from Figure 1 are of poor quality. In my opinion, photos should be taken from a greater distance. At the moment, there is no way to properly compare samples with each other. The description of Figure 1 should be changed. It is too difficult to understand the real sample composition and preparation conditions. Moreover, Figure 1 is mentioned in manuscript as a reference to the stability of solutions. In my opinion, it is not possible to specify stability of solutions from such photos. Changes of other parameters such as color or turbidity of the samples should be more discussed in text. In other way, I think that the Figure 1 should be replaced from manuscript.
•  

The figure 1 was changed macroscopic photos, schematic views of processing was presented.

 The graphs in Figure 2 should be added not as a print screen from program that was used for DLS measurements. Please, add all graphs in the same format throughout the manuscript. The text, which describing Figure 2, does not reflect the information provided in figure:

• Figure 2 was changed to histograms and TEM images of Ag-ShC under nanosec laser irradiation.

Lines 159-161: “The average diameter of ShC nanoparticles increases from 100 nm to 291.1 ± 6.4 nm under CW laser exposure and to 703.8 ± 8.9 nm under ns pulse. The most significant changes in the average size of nanoparticles were found under fs exposure: the particle size distribution pattern shows a shoulder in the range of 25–50 nm and a main peak at 500 nm.” It is clear that in case of CW laser the size increase more. However, other information is provided in text.

To meet this comment we present another set of distributions in Fig. 2, i.e. showing the effect of ns-pulse laser radiation on ShC and metal-hybrid ShC particles. We made sure that the text reflects the information presented in the figure.

Figures illustrating the distributions of ShC particles (Fig. 2) were represented as histograms rather than curves.

Moreover, the bimodal size distribution is mentioned in text. However, in my opinion the data from Figure 2 (a and b) shows that such statement is not true enough. If the peak of bigger particles on the graph of the distribution by intensity is high enough and quite low on the graph of distribution by volume, it means that probably the concentration of such particles is quite low. In such case, the distribution by number should be checked one more time. Also, the other techniques could be applied for size measurements. Also, the peak about few nm of (1) sample on Figure 1A does not clarify particle sizes and requires further explanation.

• To clarify the results presentation the figure 2 was changed. Samples under nanosec laser irradiation was shown as an example. Bimodal size distribution is clearly seen in the histograms. TEM images prove the size distribution of the particles of hybrid.
•  
• Figures illustrating the distribution of ShC particles were presented in a different form - in the form of histograms in accordance with the comments of another reviewer. Their quality has been improved and they have not been taken as screenshots from the program for DSL measurements.
•  
• In summary, the Figure 2 should be changes. Description of this figure should be revised. Moreover, additional data in form of graph or table should be added. It also should be noted, that just the distribution by intensity (as opposed to distribution by volume and number) shows the hydrodynamic radius of particles.

      The figure 2 was changed and additional data are summarized in the table 1.

• Lines 190-191: “Two broad peaks for ShC–Ag hybrid nanoparticles at frequencies 268, 391 nm, while for ShC–Au at 267, 522 nm, are observed”. It is not frequencies. Please, change to wavelengths or similar. The second peak of ShC-Au presents not at 391 nm.

-     Thank you. “Frequencies” were replaced by “wavelenghts”.

• Lines 195-197: “The peaks 522 nm for Au and 415 nm for Ag, typical of the nanoparticles of these metals in water are observed.”. In my opinion, λ_maxare not typical for Au and Ag nanoparticles in water, but for such nanoparticles of certain size.

        You are right,  the size of nanoparticles affects the position of the         absorption peak.  When nanoparticles aggregate, the peaks shift to the "red" region.

 The “typical” was changed to “are related to the presence of the nanoparticles of these metals in water.

• Lines 198-202: Please, add reference confirming this information.
•  
• It was added to the reference [24].
• The following paper confirms this information:

  Ershov B.G., Gordeev A.V. Silver nanoparticles stabilised with heteropoly anions in an aqueous solution: optical properties and electronic polarisation// Mendeleev Communications. 2001. V. 11. N4. P. 147-148. DOI: 10.1070/MC2001v011n04ABEH001462  

• Lines 204-208: “Under nanosecond exposure, the peak characteristic of ShC shifted to the short-wavelength side 249 nm for Au and to 261 nm for Ag. In the visible region, more significant changes were observed. For the dispersion containing Au it is 526 nm and 406 nm for the dispersion with Ag nanoparticles. It can be assumed that the difference between two dispersions is due to the oxidation of silver particles.” Please provide more information which difference and how can be explained by oxidation of Ag particles.

        The supposition is based on a comparison of the peaks shift for Au (chemically inert) and Ag nanoparticles. The effect may be weaken by carbon. 

•  
• Other parts of manuscript should be also additionally revised.

All the figures were improved: size of the letters in the axis increased

Fig.3 has been completely modified to include additional data.

Description corrected in text.

Fig.4,5 legends were improved

 

Reviewer 3 Report

I have only few comments and questions as follows hoping to improve quality of this manuscript.
1. It is suggested not to place acknowledgment of institutions in mid of the body text. Line 139-140
2. There seems to be few grammar issues in the abstract and body text. Please proofread the manuscript carefully. Line 18, etc.
3. The figure 1 caption (line 156-157) looks confusing to me. For "1) ShC nanoparticles....under ns pulse", why not "ShC under irradiation: a – ns, b - fs, c – CW", forming a reference group for the comparative study? Can you please give any macroscopic photos, schematic views, SEM images, for the samples or for the experiment flow? I am curious about this because expect for colors (black, yellow, brown...) I could not tell any difference of samples in figure 1. What do these colors mean?
4. The figure quality should be improved significantly. Some of the spectra axis labels are barely readable. Not sure if fig. 6 SEM images could be improved in resolution. They look quite noisy in the current version.
5. Please specify potential applications and highlight the novelty of this work. 

Author Response

We would like to express our gratitude to reviewers for reading the manuscript and for their comments. 

I have only few comments and questions as follows hoping to improve quality of this manuscript.

1. It is suggested not to place acknowledgment of institutions in mid of the body text. Line 139-140

This reminding of the Institutions was shifted to the Acknowledgements

There seems to be few grammar issues in the abstract and body text. Please proofread the manuscript carefully. Line 18, etc.

The text was corrected.

3. The figure 1 caption (line 156-157) looks confusing to me. For "1) ShC nanoparticles....under ns pulse", why not "ShC under irradiation: a – ns, b - fs, c – CW", forming a reference group for the comparative study? Can you please give any macroscopic photos, schematic views, SEM images, for the samples or for the experiment flow? I am curious about this because expect for colors (black, yellow, brown...) I could not tell any difference of samples in figure 1. What do these colors mean?

The figure 1 was changed by addition of macroscopic view and a schematic processing of the hybrids.

4. The figure quality should be improved significantly. Some of the spectra axis labels are barely readable. Not sure if fig. 6 SEM images could be improved in resolution. They look quite noisy in the current version.

All the figures were improved, size of the letters in the axis increased.

Fig.6  The images were replaced by the ones with lower magnification.

5. Please specify potential applications and highlight the novelty of this work. 

Novelty

It was for the first time that graphene-based carbon nanoparticles with hierarchical structural organization were used as a source of hybrid nanoparticles with metals. Structural reorganization of carbon nanoparticles in water under laser irradiation of various durations were observed.

Films with new hybrids were fabricated. 

The films including quantum dots and bioactive compounds (ShC and noble metals) are promising for such biomedical applications as cancer theranostics and  drag delivery, for example, dermal drag delivery.  

Scattering properties of dispersions and solid state filters (films) – Nanoparticles for laser protection.

Round 2

Reviewer 1 Report

There is no structural characterization. How to know what material is formed. Therefore, XRD and Raman should be provided. Language needs further improvement.

Author Response

 

Dear Reviewer,

Thank you for reading the manuscript.

It should be noted that the structure of shungite carbon and its nanoparticles has been thoroughly studied in different laboratories. XRD of this natural carbon has been widely presented in publications. Some of them can be found in the references of the manuscript.

We included additional description of aqueous dispersion of ShC nanoparticles preparation in the paragraph “Materials and methods” to show that composition and structure of carbon were controlled.

• Aqueous dispersions of ShC nanoparticles were prepared according the original methodology on the basis of the shungite rock powder (Shungite type I, 96 wt% carbon) [12]. Ultrasonic treatment (frequency 22 kHz, power 300 W) followed by filtration and ultracentrifugation made it possible to obtain the initial dispersion with a concentration of 0.12 g/l and pH 6.5. According to the control data of atomic absorption spectrometry and inductively coupled plasma mass spectrometry [12], all traces of non-carbon elements present in the original shungite powder are removed using the preparation procedure. We used transmission electron microscopy to avoid different carbon agglomerations apart from ShC nanoparticles.

- Well characterized ShC nanoparticles were mixed with colloidal metals.

Electron diffraction patterns were obtained with HRTEM images.  Graphitic carbon in the interface of metallic nanoparticles was observed. This structural motif preserved in the hybrids.

 Raman spectra are typical for sp²-carbons. It is shown changes in G and D peaks positions and low ratio of ID/IG that support the electron diffraction data.

There is a relationship between the intensity ratio of the lines at ~1355 cm^–1 (A1g-lattice mode, D-line) and ~1575 cm^–1 (E2g-mode, G-line) and the size of carbon crystallites, determined by x-ray diffraction. It is known a correlation between ID/IG and the value of the interlayer distance (d₀₀₂) in graphite-like crystallites.

The lower value of the ID/IG ratio in the dispersion of ShC nanoparticles compared to the initial ShC indicates that carbon is more ordered in the hybrids. The ordering of carbon is retained in films obtained by irradiation with a nanosecond laser.

The text was corrected by native English-speaking person.

Reviewer 2 Report

After revision proposed manuscript can be published after additional minor revision. The revision of English language is strongly recommended.

Author Response

Dear reviewer, 

Thank you for reading the manuscript.

The paragraph “Materials and methods” was revised.

English language of the manuscript was corrected.

Reviewer 3 Report

Thank you for addressing my comments. There is still minor mistakes in the body text. I would suggest to proofread the whole manuscript carefully.

Author Response

Dear Reviewer,

Thank you for reading the manuscript.

The paragraph "Materials and methods" was revised. 

The manuscript and English language were corrected.