Ammonia Gas Sensing Characteristic of P3HT-rGO-MWCNT Composite Films
and Nguyen Nang Dinh 1Round 1
Reviewer 1 Report
The manuscript is devoted to the preparation and investigation of structural features and sensing properties of P3HT-rGO-MWCNT composite films. The conducted research corresponds to the journal subject, however the following issues should be addressed.
1) The authors call P3HT an activator of NH3 adsorption, but do not clearly explain the reason for such an activating ability of the compound. This issue should be clarified.
2) Sections 2.1. The phrase "graphene solution" is not correct. Apparently, it is more correct to call it graphene dispersion.
3) Sections 2.1. MWCNT used for investigation should be characterized in more detail (conductivity, diameter etc.).
4) Sections 2.2. Similarly, it is better to replace “the composite solutions of P3HT-rGO-MWCNT” with “P3HT-rGO-MWCNT blends”.
5) Sections 2.3. How were the ITO grid electrodes prepared? Or are they commercially available? Please give more information.
6) The authors indicated that the thickness of the films was about 550 nm. How was it measured? The authors indicated that the thickness of the films was about 550 nm. How was it measured? Why was this particular thickness chosen?
7) Section 2.4. Line 105. Apparently, the authors meant a “EPA-2TH” prometer, not a “EPA-2TH” profilometer.
8) Section 2.4. Argon was used as a diluting and carrier gas. In real practice, the determination of ammonia in the air is of greater interest. Is it possible to use air as a diluting and carrier gas?
9) Section 2.4. Were the measurements of sensor response carried out in the flow mode, or did the researchers fill the gas flow cell with a certain amount of gas and perform the measurement in the static mode? Could the authors comment on this in a little more detail? Where did gaseous ammonia for the study come from? Was it dry ammonia? At what humidity were the measurements carried out?
10) Section 3.1. The authors attributed the peak at 29.5 degs on the diffractogram to MWCNT. What do the other peaks correspond to?
11) Section 3.2. What is the possible reason of the blue shift of the band in UV-vis spectrum of PGC-60?
12) Equation (2), apparently, should be h=(R-Ro)·100/Ro (%). Is that true?
13) Lines 222-223. The second part of the sentence “The ammonia gas molecules quickly leave the sensor surface, carrying electrons from the charged particles that are paired above” is not clear and should be rewritten.
14) Lines 240-241. Fig. 5 does not compare the sensitivity of the pristine P3HT polymer and rGO-MWCNTs-P3HT composite, as it is written in the text.
15) Figure 5. The conditions of the measurement of the sensor response (temperature and humidity) should be indicated in the caption of Fig. 5. What was the concentration of ammonia? Did you carried out all measurements of the sensor response to ammonia at 150 oC?
16) It would be useful to compare the sensor response of pristine P3HT, P3HT-rGO, P3HT-MWCNT and PGC-60 on one graph.
17) A slight drop in the sensor response over time is observed for the film PGC-60 in Fog. 5 . What could be the reason for this behavior?
18) Caption of Fig. 6 should be change. What is the difference between the sensitivity and relative sensitivity?
19) Lines 289-291. The authors claim that «…all three components in PGC sensors have significantly contributed to improvement of both the sensitivity and response time in NH3 gas sensing”, however the graphs do not show a change in the response time.
20) Please calculate the detection limit of the sensor if it is possible.
21) At the end of the discussion, a comparative analysis of the characteristics of the sensors based on the studied composites with other ammonia sensors described in the literature should be given.
Author Response
Please find attached file.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors have prepared a conducting polymer hybrid for gas sensing and shown its robustness in reversible sensing of ammonia gas. The material is well characterised using both electrical and imaging techniques. However, in saying that they are missing some experiments. The introduction needs to be a bit more robust and the authors should also include a table to show their gas sensor behaves relative to recently reported work. I only recommend publication if the below mentioned comments are addressed.
- English and grammar needs to be corrected throughout before publication.
- The introduction needs to be rewritten to help the readers understand the focus of this work. What is the point of developing the hybrid material for sensing? They are also missing some key references in the introduction on the latest work for gas sensing using conducting polymers. There are also other conducting polymers such as PANI and PPY that are more gas sensitive as compared to PEDOT and that should be discussed in the introduction. Some important references are listed here.
- https://www.sciencedirect.com/science/article/pii/S2589152920302842
- https://pubs.rsc.org/en/content/articlehtml/2021/tc/d0tc05719c
- https://pubs.acs.org/doi/abs/10.1021/acsomega.0c06272
- https://www.sciencedirect.com/science/article/pii/S1388248117303545
- https://pubs.rsc.org/en/content/articlehtml/2020/tc/d0tc02856h
- It is unclear what advantage MWCNT provided the developed hybrid material. Clarification is needed in the introduction.
- Please adjust fig 1 so that it is on the same page as the caption.
- Why was dropcasting used to deposit the sensing material? Was a homogeneous film observed? Did the authors see a ‘coffee-stain’ effect because of the drying?
- Why was Ar gas used the carrier gas. It doesn’t simulate real conditions. Nitrogen and Oxygen is a much better alternative to simulate real conditions.
- Figure 5 needs to be clearer. What was the concentration used? Can the authors explain the drift seen in the sensing response?
- The authors should include a table showcasing recently developed conducting polymer gas sensors and show how their response compares to their work.
- They need to show how the response compared in the presence of humidity as it is a major issue with conducting polymer based gas sensors.
Author Response
Please find the attached file.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors responded to all the comments of the reviewers, but the text contains many typos that should be corrected before the article is accepted for publication.
Author Response
Comment: The authors responded to all the comments of the reviewers, but the text contains many typos that should be corrected before the article is accepted for publication.
Response: Thank you for your comment. We have revised the manuscripts carefully so that typos have been corrected.
Reviewer 2 Report
The authors have made significant changes to the manuscript and it reads much better now. However I still suggest the inclusion of a table showcasing recently developed conducting polymer gas sensors and show how their response compares to their work.
Author Response
Comment: The authors have made significant changes to the manuscript and it reads much better now. However I still suggest the inclusion of a table showcasing recently developed conducting polymer gas sensors and show how their response compares to their work.
Response: Thank you for your comment. Table 1 was added on page #7 for comparison.
