Rapid synthesis and characterization of silver-loaded graphene oxide nanomaterials and their antibacterial applications

With the promising potential application of Ag/graphene-based nanomaterials in medicine and engineering materials, the large-scale production has attracted great interest of researchers on the basis of green synthesis. In this study, water-soluble silver/graphene oxide (Ag/GO) nanomaterials were synthesized under ultrasound-assisted conditions. The structural characteristics of Ag/GO were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersion spectroscopy, respectively. The results showed the silver particles (AgNPs) obtained by reduction were attached to the surface of GO, and there was a strong interaction between AgNPs and GO. The antibacterial activity was primarily evaluated by the plate method and hole punching method. Antibacterial tests indicated that Ag/GO could inhibit the growth of Gram-negative and Gram-positive bacteria, special for the Staphylococcus aureus.


Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
In this work, the synthesis and characterization of silver-loaded graphene oxide nanomaterials have been systematically investigated. The antibacterial test has been also conducted by two methods. I recommend this paper for publication after minor revision. Here listed some issues should be clarified. 1.
the abstract is hard to read and master what the authors want to demonstrate? Please reorganization to make the manuscript to understand. 2.
The literatures in the introduction section can not well cover the research progress of Graphene oxide, Metal nanoparticles, Sonochemical synthesis and so on. please add some related paper in the revision. 3. Figure 4 is used to prove graphite powder has been successfully oxidized and GO surface oxidation produces many oxygen-containing groups. However, the absorption peak at ~1728cm-1 is too small to observe, please magnify this peaks.

4.
Diameter of bacteriostatic zone in Figure 11 should be measured. 5. Authors should carefully check the grammar throughout the manuscript. 6. Is there any effect of ascorbic acid concentration and pH of the solution on the size and aggregation of AgNPs on GO? 7. Why did the author choose ultrasound assisted AgNPs synthesis instead of microwave-assisted in the experiment? 8. What is the effect of Ag particle size on antibacterial activity?

Decision letter (RSOS-201744.R0)
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Dear Dr Ni:
Title: Rapid synthesis and characterization of silver-loaded graphene oxide nanomaterials and their antibacterial applications Manuscript ID: RSOS-201744 Thank you for your submission to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
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1. The review of literature suggests that previous successful attempts have been made to develop the Ag nanomaterial as well as its antimicrobial activity so pertaining to this novelty of this investigation has to be clarified in more detail.
3. The growth mechanism for the formation of nanomaterial Ag/GO should be explained in more detail based on the chemistry concept.
4. In the Bacterial Cell viability assay, as the concentration of nanomaterial is increased from 12.5% -100% the cell viability is increasing, this is contradictory to it being applied as an antimicrobial agent. Kindly Give a detailed justification.

5.
For an antimicrobial agent the minimum concentration of substance should be effective. So the calculations pertaining to be MIC has to be done. As high concentration would be toxic to other living cells.

Reviewer: 2
Comments to the Author(s) In this work, the synthesis and characterization of silver-loaded graphene oxide nanomaterials have been systematically investigated. The antibacterial test has been also conducted by two methods. I recommend this paper for publication after minor revision. Here listed some issues should be clarified. 1. the abstract is hard to read and master what the authors want to demonstrate? Please reorganization to make the manuscript to understand. 2. The literatures in the introduction section can not well cover the research progress of Graphene oxide, Metal nanoparticles, Sonochemical synthesis and so on. please add some related paper in the revision. 3. Figure 4 is used to prove graphite powder has been successfully oxidized and GO surface oxidation produces many oxygen-containing groups. However, the absorption peak at ~1728cm-1 is too small to observe, please magnify this peaks. 4. Diameter of bacteriostatic zone in Figure 11 should be measured. 5. Authors should carefully check the grammar throughout the manuscript. 6. Is there any effect of ascorbic acid concentration and pH of the solution on the size and aggregation of AgNPs on GO? 7. Why did the author choose ultrasound assisted AgNPs synthesis instead of microwave-assisted in the experiment? 8. What is the effect of Ag particle size on antibacterial activity?
Author's Response to Decision Letter for (RSOS-201744.R0) See Appendix A.

Decision letter (RSOS-201744.R1)
The editorial office reopened on 4 January 2021. We are working hard to catch up after the festive break. If you need advice or an extension to a deadline, please do not hesitate to let us know --we will continue to be as flexible as possible to accommodate the changing COVID situation. We wish you a happy New Year, and hope 2021 proves to be a better year for everyone. *************************** Dear Editor/Reviewers: First of all, we would like to thank the reviewers of our paper (RSOS-201744) for his/her constructive and informative comments and suggestions. We have carefully considered the reviewer's comments and suggestions and have modified our manuscript accordingly. The following is our detailed response to the reviewer's comments and suggestions. For clearance, we have listed the reviewer's comments below and have addressed them one by one.

Reviewer Comments:
Reviewer: 1 Comments to the Author(s) In this report, the authors reported the preparation of Ag/GO nanomaterial and its applications as antimicrobial agents. This manuscript needs a major revision and rereview. The comments are given below. 1. The review of literature suggests that previous successful attempts have been made to develop the Ag nanomaterial as well as its antimicrobial activity so pertaining to this novelty of this investigation has to be clarified in more detail. Following references about different novel Ag/GO bases nanomaterials developed with their multifunctional properties are metioned ACS Appl. Mater. Inter. 8, 19038-19046. (doi:10.1021/acsami.6b06052), Colloids Surface B 159, 366-374., Coordin. Chem. Rev. 357, 1-17. Ultrason Sonochem. 39, 577-588. Our response: It is a good suggestion. The main purpose of this paper is to synthesize Ag/GO nanomaterials through the green method. And the ultrasound-assisted synthesis offers exceptional advantages over other approaches such as surfactant free, low temperature and so on. More detailed comparison or depiction has been clarified in the revised manuscript.
2. In the preparation process of Ag/GO, on what basis, the amount of reagents ultrasound time and ultrasound power were determined? Were the high combination of GO and Ag tried with 10min, 30min for ultrasound synthesis. Our response: In the preparation process of Ag/GO, the basic reaction conditions were determined by the reference (Acar Bozkurt, P. 2017. "Sonochemical Green Synthesis of Ag/Graphene Nanocomposite." Ultrason Sonochem 35: 397-404). And the longer ultrasonic time selected in this paper would be beneficial to the formation of Ag nanoparticles on graphene surface and the dispersion of Ag/GO nanocomposites. The SEM (as following picture shows) showed that the silver ions can be transformed into silver nanoparticles and deposited on the surface of graphene oxide within the set time.