Theoretical and Experimental Research on Ammonia Sensing Properties of Sulfur-Doped Graphene Oxide
Round 1
Reviewer 1 Report
In the manuscript entitled “Theoretical and experimental research on ammonia sensing properties of sulfur doped graphene oxide”, Y. Yu et al. have proposed sulfr-doped graphene oxide as sensing layer to detect ammonia gas at room temperature, evaluating also theoretical models to explain the sensing performance.
First of all, in the manuscript a lot of grammar errors are reported; for example, please, correct in the abstract at line 12, “sulfur” instead of “sulfer”.
In the abstract, the sentences “the detection response and recovery time of S-GO gas sensor to NH3 are relatively short. And the sensing limit to ammonia at RT is 0.5ppm.” are formally incorrect, please correct.
In the introduction, at page 1 line 21, the assertion “Ammonia is a kind of volatile organic gas” is not correct, since ammonia is not a VOC but is classified as inorganic gas.
In the introduction, at page 1 line 21, the assertion “...which widely exists in nature.” has no sense, please, discuss.
In the introduction, reduce the first paragraph and add more references.
In the introduction, the authors should indicate the common set-up used to detect ammonia gas, evidencing their advantages and disadvantages, and adding the correct references.
In the introduction, more details should be added on the application of graphene as sensing layer, briefly indicating its use as ammonia gas sensor reported up now in literature. Moreover, the authors should add a table reporting the best obtained results using graphene as ammonia sensing layer, indicating the gas concentration range used for analyses, the transduction mechanism of the sensor, the sensor sensitivity and selectivity.
In the introduction, the authors should motivate their proposed sensing materials, adding references regarding the sulfur-doping of graphene oxide, discussing on the choice of graphene oxide and not of reduced graphene oxide. Moreover, they should briefly indicate the commonly used procedure to sulfur doping graphene oxide, adding reference, and motivating their chosen procedure. Finally, they should list the common used graphene-based gas sensors, evidencing the transduction mechanism, and they should indicate and motivate the used sensor system.
In the introduction, the authors should also briefly add their best obtained results, indicating the value of sensor response and of sensor selectivity towards the ammonia respect to the other investigated gases.
In materials and methods section, the authors should indicate all the chemical reactions.
In the material and methods section, the authors should indicate all the instruments used to analyses the sensing materials, adding also the operating conditions during the analyses.
The authors should add references regarding the equations used for gas sensing measurements; moreover, equation (2) is not complete, the authors should multiply it for 100, to obtain the response expressed in percentage.
In the material and methods section at page 4 line 124 the following assertion “The reaction time is the time between the gas in and the resistance 1 reached 90% of the stable resistance.” is conceptual wrong; it is not a chemical reaction at all; therefore, please, correct and refer to sensing mechanism.
The authors should indicate the type of developed gas sensor; which is the transduction mechanism?
The authors should indicate the equations related to the response time and recovery time.
The authors should indicate not only the investigated concentration range for ammonia but also for the reported interfering gases, those indicated in Figure 7.
The authors should add the formula to obtain the gas selectivity, adding reference.
Which is the gas carrier? Please, indicate it.
Which is the relative humidity during the sensing analyses? Please, indicate it.
Considering the SEM images reported in Figure 3, the material seems to be fibre-like and not a homogeneous film; therefore, it is not possible to do an elemental quantitative analyses by EDS. Please, discuss. Moreover, from EDS and the only FTIR analyses is not possible to distinguish graphene from oxidized and reduced oxidize graphene. Please, discuss.
Please, correct the FTIR spectra with the baseline.
Please, add a table indicating all the detected FTIR signals.
The presence of the band at 1260 cm-1 is not so evident. I suggest to evaluate IR in ATR mode.
Regarding the sensing measurements, I suggest to report the sensor cure at different ammonia concentrations but with a recovery time between two expositions, in this way it would be evaluate a possible drift of the baseline.
I suggest to report a plot of the sensor response versus the ammonia concentration, reporting the error bar for each value; indeed, which is the sensing reproducibility and the sensor stability? Discuss.
To evaluate the sensor selectivity, the authors should measure the sensor response in presence of a gaseous mixture containing various concentration of the analysed gas in presence of interfering gases.
In Figure 7, the authors should report the sensor sensitivity (taking into account the sensor response in the evaluated gas concentration range) towards the various analysed gases.
The authors should report a possible sensing mechanism, adding references.
The English style of the manuscript should be improved.
I can accept this manuscript with major revisions.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper, gas sensing characteristics of ammonia on Sulfer-doped graphene oxide(S-GO) were investigated. I think that there are still many problems to be solved 1. What is the molecular structure of S-GO? It is very important for first-principles calculations. 2. Sulfur doped graphene oxide (S-GO) was synthesize, why did the author use the S-G model in Fig. 9? 3. The quality of Fig. 10 is bad, and figures in it should be aligned with a uniform font size. Meanwhile, it is easy to calculate the information exhibited in Fig. 10 by CASTEP program, why did the authors quote them from Refs [35-37]? 4. The review can not find Fig. 7(b), as written in Line 183. 5. How did the author obtain the result of “S-GO sensor also showed excellent selectivity to 307 different kinds of gases” in Section Conclusions? There is no evidence in the manuscript for it. 6. There are many grammar and spelling mistakes in the manuscript.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
In my opinion, the revised version of the manuscript is acceptable for publication.
Author Response
The english language and style in the manuscript has been modified. Thanks.
Reviewer 2 Report
The author answers some questions, and others may be difficult to solve in a short time. The quality of some graphs in the manuscript should be improved.
Author Response
The English language and style in the manuscript has been modified. And the quality of the graphs in the manuscript have been improved.
