Enhanced Photothermal and Photoacoustic Performance of Graphene Oxide in NIR-II Biowindow by Chemical Reduction
Round 1
Reviewer 1 Report
The manuscript entitled “Enhanced photothermal and photoacoustic performance of graphene in both NIR-I and NIR-II biowindows by vacancy-defect engineerings” by Xiaoye Su , Liantong Li , Dandan Cui , Wei Fang and Yujiao Shi describes the preparation of graphene samples from graphene oxide sheets, provides a description of their morphological and chemical features, and illustrates their use in photothermal and photoacoustic experiments. The subject matter is interesting and worthwhile. However, in my opinion, its overall discussion is totally misleading, because the authors put an exclusive accent on the notion of defect engineering, while defects only occur as a byproduct in a process of reduction that is clearly dominant. It seems from the title, the abstract, the intro and throughout the text that this paper compares graphene samples with different levels of vacancy defects. However, I understand that it actually compares graphene oxide samples with different degrees of reduction from none to 100%, where the process chosen for reduction also happens to introduce vacancy defects. Seen from this perspective, it is actually well known that graphene just absorbs more light than graphene oxide.
Additional issues:
“After that, the water-soluble graphite oxide is chemically or thermally reduced to biocompatible graphene sheets.” Why biocompatible?
“… the produced VD-G samples become porously micro-structured with obvious microscopic pores, indicating an enhanced reduction of the graphene oxide.” Why? Is there any relevant ref?
“These results indicate that, the porosity grows with the VD degree increases.” Can the authors please provide an explanation for the correlation between atomic vacancies and micro-porosity?
In my opinion, this manuscript should be rewritten from title to end, in order to explain that it provides additional evidence for the importance to thoroughly reduce graphene oxide for applications in photothermics and photoacoustics. The creation of vacancy defects is just a collateral effect, and there is no evidence that graphene with vacancies is more efficient than graphene without vacancies.
Author Response
We appreciate the Reviewer’s constructive comments and suggestions. All authors have carefully studied the comments from Reviewer’s #1, #2, #3 and #4. The Reviewer’s comments are italicized and the authors' response is listed below each comment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript presents vacancy-defected graphene (VD-G) as agents for PT and PA enhancement. Different defect degrees of the VD-G samples were first prepared and characterized in detail, including SEM, TEM, Raman shift spectra, etc. Then, optical absorption spectra were measured to show the enhanced absorption of VD-G samples. PT enhancement wad done by in vitro samples, and PA enhancement was demonstrated both in vitro and in vivo, showing good performance of the fabricated VD-G samples. The work is technically sound, and the manuscript is clearly written. To further improve the manuscript, there are some comments from the reviewer.
- At line 130, the characteristic factor g of 2.0023 is calculated. Is the characteristic factor g the same as EPR signal intensity in Fig. 2(e)? If not, what are their relations? Please make it clear.
- In Fig. 3(b), the absorption amplification in NIR-I and NIR-II is calculated. Does the authors do the estimation by the average enhancement over the whole NIR-I (or NIR-II) range in Fig. 3(a), or by the enhancement of a certain wavelength within the NIR-I (or NIR-II) region? Please make it clear.
- In Fig. 5(c), in vivo B-scan PA imaging is demonstrated. Would the authors provide the information of the rough depth (below the tissue surface) where the VD-G samples were injected and imaged? From Fig. 5(c), it seems that the VD-G samples were at the superficial layer.
- Besides the stability demonstrated in Fig. 6, there may be more concerns before the VD-G can be used in practical/clinical applications. Would the authors discuss more properties of the proposed materials (e.g., toxicity, biocompatibility, biodegradability, etc.)?
- There are a few typos in pages 4 and 5.
(1) Line 110, it should be “Figure 2(b)”?
(2) Line 112, “carbon atoms,.” The comma should be deleted?
(3) Line 119, “VD degree increases,” The comma should be period?
(4) Line 124, “the intensity ratio ID/IG” ID and IG are not defined. Do ID and IG indicate the intensity of D peak and G peak, respectively? If so, please define them.
(5) Line 129, it should be “Fig. 2(e)”?
Author Response
We appreciate the Reviewer’s constructive comments and suggestions. All authors have carefully studied the comments from Reviewer’s #1, #2, #3, #4 and #5. The Reviewer’s comments are italicized and the authors' response is listed below each comment. Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript by X. Su, L. Li, D. Cui, W. Fang and Y. Shi has undergone some revision. In particular, the authors have agreed that their work was about a comparison between different models of reduced graphene oxide with different levels of chemical reduction, rather than different models of graphene with different densities of vacancy defects, as it was presented in the original submission. Of course, the scope of the work has completely changed from one version to the next. However, the authors have done nothing but update a few words, i.e. essentially from defect-engineered graphene to chemically reduced graphene oxide, and made no other change to their intro, discussion, etc.. For instance, although it has now become the main subject of the manuscript, it is never said that it is already known that the optical absorbance of graphene oxide increases upon chemical reduction into graphene (see e.g. https://doi.org/10.1364/OE.22.019375, https://doi.org/10.1016/j.ejbas.2016.11.002, https://doi.org/10.1021/ja2010175, and many more). As a result, the present manuscript is out of context, and requires a thorough revision before resubmission, in order to justify its position within the current debate.
In some cases, a crude substitution of words has resulted into an overall loss of meaning.
Below are some examples:
“After that, the water-soluble graphite oxide is chemically or thermally reduced to water-soluble graphene oxide sheets.” I have not understood this step.
“More specially, reports have shown that, this chemical reduction treatment is one of the mostly used strategies for triggering chemical reduction in 2D materials with different degrees of reduction by controlling the dosage of the reducing agent [21,22].” This sentence is recursively tautological.
In addition, some sentences seem to be in the wrong place, like “TVS-200EX,NEC Avio Infrared Technologies Co.,Ltd, Japan) was used to realtime monitor the temperature. The laser power is controlled to be about 100 mW, and the laser spot size is about 5 mm. The signals and the thermal images were collected by using thermal camera.”
“… which resulted in 47±5% positive enhancement and 33±5% negative decrement in T1- and T2-weighted MR imaging, respectively.” Please expand on the concept of negative decrement in T2-weighted MRI here.
Overall, this manuscript requires a careful revision, one that goes much beyond the replacement of single words here and there. What is already known about the subject matter of this work, i.e. the increase in optical absorbance of graphene oxide upon reduction into graphene, and its use in photothermal and photoacoustic applications? What is the progress made with respect to the state of the art?
Finally yet importantly, I have seen no ethical statement for the use of mice.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
