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  • Ki-Hyun Pyo1,
  • Ji-Sun Kim1 and
  • Yoon Hee Jang2
  • et al.

Reviewer 1: Anonymous Reviewer 2: Anonymous Reviewer 3: Anonymous

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors did not address the substantive comments contained in the review. The substantive content of the article is unacceptable.

Comments below: 1. Fig. 2a) shows a schematic of the sensor, not its actual image. Why don't the authors include an actual image of the sensor?

  1. Lines 202-230 - Since acetone interacts weakly and water interacts more strongly, the direction of resistance change should be the same. Why don't the authors consider that the surface of P(ANi-co-ASNi) spherical NPs is coated with CSA? The authors contradict themselves in this paragraph. Which dipole-dipole interactions are stronger with water or acetone?
  2. Lines 260 and following: How can a coating be a dopant? The interactions between P(ANi-co-ASNi) and CSA are surface, not bulk. If there are two different layers, an electrical double layer always forms at their boundary, which affects the overall resistance of the structure.
  3. "In the CSA-capped P(ANi-co-ASNi) structure with an ANi-to-ASNi molar ratio of 0.5:0.5, the sulfonic acid ion of CSA is believed to interact with P(ANi-co-ASNi) via the π-conjugated chain, resulting in protonation at the imine nitrogen sites." – Why does this only happen at an ANi to ASNi ratio of 0.5:0.5?
  4. Lines 334 to 343 – Why the reference to exhaled air? Acetone is present in exhaled air at concentrations below 1 ppm, but the humidity of exhaled air is above 90% RH, not 1 to 5%!
  5. Line 420 - If it doesn't form a continuous layer, how does it improve the resistance of the P(ANi-co-ASNi) nanoparticle to humidity?
  6. Lines 505 and following - Water aggregates and condenses above 90% RH!

Author Response

Please refer to the attatched file

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The study entitled: "Synthesis of CSA-capped Poly (aniline-co-aniline-2-sulfonic acid) Spherical Nanoparticles for Gas-Sensor Applications" brings the advantage of significant performance for acetone gas detection having stability  to varying temperature and humidity.

The most visible weakness of the manuscript is represented by a not appropriate structure of the material. This brings undesired repetitions and add a difficult reading. Titles and sub-titles are demanded: The main optical properties of the sensing material; The Raman analysis of the polymer; the response/recovery time; sensitivity tests............ I listed them.

Some shortcomings are:

  1. Editing English language: Abstract line 19: please correct "suoerior" and thoroughly check all the text.
  2. Please attribute each reference of the group [6-10] to the specific application.
  3. The same request as for 2. for [11-14] and it seems more references are demanded to justify the text.
  4. On page 2, line 66. Please complete: Which is the gas that was detected?
  5. Many repetitions are present in the text belonging to page 2, line 70-90. Please reformulate to avoid repetitions, for instance "Specifically, PANi substituted with an -SO3H group is expressed as poly(aniline-2-sulfonic) (PASNi)." lines 79-80 and lines 88-89.
  6. The information on page 3, lines 135-140, needs a sub chapter, because is has to be clearly noticed.
  7. Verify the electrode pattern (dimensions: 4 mm × 9 mm; line width: 0.2 nm) or 9 mm × 4 mm × 0.03 ㎛. Is it 0.2 nm or 0.3??? and please keep the same sequence length × width × height in the text and in figures (Figure 2).
  8.  General remark: Please use more paragraphs to make the text more accessible and understandable. Some paragraphs needs a sub-section title.
  9.  Many repetitions that are not required between 2-2. Synthesis of CSA-doped P(ANi-co-ASNi) spherical particles  and 3. Results and Discussion
  10. In 3. Results and Discussion, please re-structure the text based on microscopy, optical and Raman analysis and introduce a very specific title beginning with DETECTION -on page 7 line 334. 
  11. Please introduce a distinctive title  "Presumed mechanism of detection" and move all the appropriate texts in this section. Make specific fundaments for acetone and for water detection.
  12.  Sub-sections for; The response/recovery time; Sensitivity tests to different gas concentrations; ............, Selectivity tests,
  13. Selectivity tests have to be presented in a diagram in comparison with acetone gas.
  14. Conclusions are mixing the sensor performances with material characteristics, please align them in a proper order.
  15. BET analysis of the sensing polymer should offer great details regarding the surface morphology. Introduce it if possible. Porosity information and rugosity will be of great help to understand the mechanism of detection.

Author Response

Please refer to the attatched file

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Obs.1. By using “water vapor concentration” expression do the authors refers to the actual amount of water vapor in the air? simply denoted as water in its gaseous state. “Water vapor concentration” cannot be expressed as absolute humidity (AH): grams of water vapor per cubic meter of air (g/m³)?

Please insert an explanation so that the expression in which the authors state: "... the performance of the sensors in detecting different concentrations of water vapor in the absence of humidity" is made clearer.

Obs.2. In Figure 6 [I] and [II] the name of the substance is missing, even though it is mentioned in the legend.

Obs.3. In cap. Introduction the authors declare: “… in detecting various organic gases such as … carbon dioxide CO2, hydrogen H2 …”

Organic compounds are not defined as molecules that contain carbon atoms bonded to hydrogen?

Obs.4. cap.2-3.  “… maintaining an interelectrode distance of 0.5 mm”. If the electrodes are deposited, in advance, they have a fixed distance. If a distance is maintained there, then there is a regulation system.

Obs.5. 5 ppm acetone gas must have something else as a majority gas, as a carrier. It is dry air, nitrogen or something else?

Obs.6. “… into a small vacuum chamber at a flow rate …” This enclosure is no longer a vacuum chamber unless a vacuum pump continuously evacuates the atmosphere from inside the chamber, when a gas was introduced, the vacuum was lost.

Obs.7. The authors fail to mention the used sensor for measurement or humidity control when the resulting gaseous H2O is blended with dry air.

Obs.8 . Please correct: ” suoerior” in cap. Abstract.

Author Response

Please refer to the attatched file

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors In response to comment 7, the authors wrote, "Beyond this threshold, H₂O molecules tend to aggregate and physically accumulate on the sensor surface, forming a thin moisture layer. This localized water clustering and partial liquefaction likely interfere with the functional engagement between the capping agents and the PANi backbone, thereby increasing the electrical resistance. This effect is further amplified under low-temperature conditions, where the formation of nanoscale water films occurs at relatively lower RH levels, indicating a temperature-dependent modulation of the sensor's humidity response." This is a very good and logical statement by the authors. They should now carefully review the manuscript and, accordingly, revise it in other places, e.g., lines 188 and following. How can acetone or water interact with NH+ groups when P(ANi-ASNi) is coated with CSA? First, acetone or water must interact with CSA, and the consequence of this interaction is a change in the conductivity of P(ANi-ASNi)!!! Other comments: Regarding the statement "This heterogeneous shell architecture enhances charge transport at the core–shell interface, improves resistance to ambient humidity, and facilitates effective interactions with organic gas molecules." – I disagree that this system improves resistance to ambient humidity. Regarding the statement "enhanced conductivity due to the CSA-induced structural modification." – according to the reviewer, CSA does not cause structural changes, and the improved conductivity is caused by chemical-physical interactions at the P(ANi-ASNi) and CSA interface!

Author Response

Please refer to the attached file

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The Authors responded to the most part of comments & suggestions, so I agree that as it is now, the manuscript deserves to be published. 

Author Response

Thank you for your review.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors implemented my observations.

Author Response

Thank you for your review

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

I completely disagree with the authors' explanations. These explanations do not agree with the basic properties found in Organic Chemistry textbooks. How can a substance with the following properties be a porous layer permeable to water or acetone?

Camphorsulfonic acid (CSA) (or Reychler’s acid), is a white crystalline powder, hygroscopic, very soluble in ethanol and melts at 198 °C., [Synlett 2009, No. 4, 683–684]. It is a strong acid soluble in organic solvents too. Therefore, even if, as the authors claim, it forms a porous layer on the surface of the P(ANi-ASNi), both water and acetone will interact with it. Consequently, these interactions will change the interactions between the P(ANi-ASNi) and CSA.

Furthermore, I asked the authors to carefully review the manuscript and correct the errors. The manuscript still contains substantive errors, for example:

"Furthermore, the sensors exhibited superior stability across varying temperature, humidity, and cyclic performance, outperforming conventional pure PAN." - If the sensor exhibits a strong response to water vapor, how can we speak of better stability? Air with a humidity of 1% RH is very dry!!!

"The P(ANi-co-ASNi) copolymer exhibits p-type semiconducting behavior, attributed to NH⁺ sites within its backbone that interact with polar molecules such as acetone and H2O via hydrogen bonding and electrostatic forces." - If both types of molecules form hydrogen bonds, the direction of resistance change must be the same! But it isn't!

“The CSA layer, deposited on the positively charged core, forms a porous thin film with irregularly distributed particulate domains, inducing a doping effect that enhances conductivity while serving as a protective barrier.” – How can a hygroscopic compound be a barrier and exhibit hydrophobic properties?

Author Response

Please refer to the attached file

Author Response File: Author Response.pdf