Enhanced Electrocatalytic Properties of Co₃O₄ Nanocrystals Derived from Hydrolyzed Polyethyleneimines in Water/Ethanol Solvents for Electrochemical Detection of Cholesterol

Round 1

Reviewer 1 Report

The present study describes the effect of hydrolysis of polyethylenimine in water/ethanol mixture on the morphology of the cobalt oxide (Co3O4), used as the main sensor component.

Method:

1-     In scheme 1, this part presented is different than what is written in the experimental part . Therefore, in this way the schematic presented in the manuscript is misleading. Author need to modify the Scheme-1 with more closely representative process.

2-     Minimize the y-axis of the part in order to make the peaks of XRD patterns of Co3O4 more clear.

3-     Authors should add the infrared reflection–absorption spectroscopy (IRAS) study of cholesterol oxidase immobilized Co₃O₄ nanocrystals.

4-     Some typo’s and editing mistakes to be removed.

 

 

 

Author Response

 

 

Reviewer 1

 

Comments and Suggestions for Authors

The present study describes the effect of hydrolysis of polyethylenimine in water/ethanol mixture on the morphology of the cobalt oxide (Co3O4), used as the main sensor component.

We are thankful to the reviewer useful comments in improving the quality of manuscript prior to publication

Method:

• In scheme 1, this part presented is different than what is written in the experimental part . Therefore, in this way the schematic presented in the manuscript is misleading. Author need to modify the Scheme-1 with more closely representative process.

Ans. We acknowledge the reviewer comment and thanks. We have modified the scheme as per reviewer suggestions and we believe that the revised scheme will satisfy the reviewer comment.

• Minimize the y-axis of the part in order to make the peaks of XRD patterns of Co3O4 more clear.

Ans. The XRD patters with respect to Y-axis are minimized and new modified image is enclosed in the revised manuscript.

• Authors should add the infrared reflection–absorption spectroscopy (IRAS) study of cholesterol oxidase immobilized Co₃O₄

Ans. We understand the reviewer comment about the  IRAS of Co3O4 nanocrystals after the immobilization of cholesterol oxidase, however we are unable to provide the IRAS in the revised version of manuscript due to out of order instrument

4-     Some typo’s and editing mistakes to be removed.

Ans. We have tried to remove the typos and mistakes throughout the revised version of manuscript

Reviewer 2 Report

Comments:

Manuscript ID: catalysts-1930064

In this work, the author reported, “Excellent electrocatalytic properties of Co₃O₄ nanocrystals derived from hydrolysed polyethylenimine in water/ethanol solvents for electrochemical detection of cholesterol”. The synthesized material is well characterized, and the electrochemical data indicates good analytical outcomes. This is an interesting article, but in which several major aspects must be explained and/or corrected, and experimental work must be performed for reconsideration.

1.     Please do not use "excellent" in the title.

2.     It should reconstruct the content abstract and the length of the introduction part. Authors should maintain a single frame of language understanding and phrase maintenance throughout the paper.

3.     The author should explain using expansive gold-coated glass for cholesterol detection since some cost-effective electrodes are used to detect cholesterol with good analytical outcomes.

·        Biosensors and Bioelectronics 63 (2015): 212-217.

·        RSC advances 5, no. 79 (2015): 64146-64155

·        Etc.,

4.     Reference should be uniform style. There are some typo mistakes in the references. The author should take this into account more carefully.

·          Ex. Ref. 19 does not contain paper tile.

·          Ref. 20 typo mistake

·          Ref. 47, 48 typo mistakes

·          , etc.,

5.     The author should perform FT-IR analysis in order of the functional group since the author used polyethylenimine.

6.     What is the essential role of polyethylenimine assisted synthesis of Co₃O₄? The author should discuss this elaborately.

7.     In the product synthesis, the amount of solvent, the company, and purity of the chemicals, are not present. I wonder if other researchers can try to reproduce it.

8.     What is the sensor's response with respect to time in the curve? It should be included in the revised manuscript.

9.     The author did not explain the limitations of the sensor. Should I assume that there are no limitations? It would be nice if they say the future perspectives and their limitations which can attract more readers.

10.  The authors did not discuss anything about fouling. I am expecting that there would be electrode fouling while analyzing these analytes.

11.  The comparison table is essential to this work in order to describe the efficiency of the proposed sensor with other works. The author should give a comparison table in the revised manuscript.

12.  The typos and grammatical errors are scattered throughout the paper and must be corrected with the utmost care.

 

 

Author Response

 

 

 

Reviewer 2

Comments and Suggestions for Authors

Comments:

Manuscript ID: catalysts-1930064

In this work, the author reported, “Excellent electrocatalytic properties of Co₃O₄ nanocrystals derived from hydrolysed polyethylenimine in water/ethanol solvents for electrochemical detection of cholesterol”. The synthesized material is well characterized, and the electrochemical data indicates good analytical outcomes. This is an interesting article, but in which several major aspects must be explained and/or corrected, and experimental work must be performed for reconsideration.

1. Please do not use "excellent" in the title.

Ans. The title has been modified in the revised version of manuscript

2. It should reconstruct the content abstract and the length of the introduction part. Authors should maintain a single frame of language understanding and phrase maintenance throughout the paper.

Ans. These changes are made throughout the manuscript during revision wherever necessary as per reviewer comments

3. The author should explain using expansive gold-coated glass for cholesterol detection since some cost-effective electrodes are used to detect cholesterol with good analytical outcomes.

• Biosensors and Bioelectronics 63 (2015): 212-217.
• RSC advances 5, no. 79 (2015): 64146-64155
• Etc.,

Ans. We understand the reviewer comment about the fabrication of electrode, we used a very thin layer of gold onto glass slide, yes from cost point of view reviewer concern is appreciated, however from performance point of view and the simplicity of fabrication of our proposed strategy is better opening for the large Production of electrodes. For the two citations reviewer described here, if we see the authors have utilized the glassy carbon electrode which is still expensive but the performance of reported works is poor for higher levels of cholesterol and our biosensor has wide linear range compare to these reported works.

4. Reference should be uniform style. There are some typo mistakes in the references. The author should take this into account more carefully.

• Ex. Ref. 19 does not contain paper tile.
• Ref. 20 typo mistake
• Ref. 47, 48 typo mistakes
• , etc.,

Ans. The reference style and uniformity is maintained in the revised version of manuscript

5. The author should perform FT-IR analysis in order of the functional group since the author used polyethylenimine.

Ans. We fully understand the reviewer comment about the FTIR results in the revised version of manuscript, and we polgize not to provide this data as our instrument at the lab is out of order. For more clealrifcation, we have combusted the material in the air for 4h at 400 ^oC and we believe that many of the functional groups could be changed into gaseous products and released at the time of combustion and we have only the Co3O4 phase as fully confirmed from XRD results and EDS data.

6. What is the essential role of polyethylenimine assisted synthesis of Co₃O₄? The author should discuss this elaborately.

Ans. In the revised manuscript, we have provided the expected role of polyethylenimine towards synthesis of Co3O4. In principle, the long chains of hydrocarbon along with amine functional groups play a vital role in driving the crystal orientation of cobalt oxide and consequently well controlled cobalt oxide nanocrystals are obtained. Another role during the growth reaction, the long hydrocarbon chains increase the nucleation of cobalt oxide and the amine functional groups accelerated the growth kinetics by providing the abundant source of hydroxyl groups when amine reacted with the water. These possible observations are added in the revised version of manuscript. Beside this, the polyethylenimine assisted the cobalt oxide towards enhanced sensitivity, limit of detection and linear of cholesterol which was the main aim of our proposed study.

7. In the product synthesis, the amount of solvent, the company, and purity of the chemicals, are not present. I wonder if other researchers can try to reproduce it.

Ans. The required information about the materials and solvent are added in the revised version of manuscript

8. What is the sensor's response with respect to time in the curve? It should be included in the revised manuscript.

Ans. The sensor response  is about 1-3 s and it is provided in the revised version of manuscript

9. The author did not explain the limitations of the sensor. Should I assume that there are no limitations? It would be nice if they say the future perspectives and their limitations which can attract more readers.

Ans. We thank you to the reviewer for useful comment and fully agree that there is always space for future studies and the limitations. The sensor has limitation of fabrication of electrode where the sensor can be employed especially at the cellular level for the monitoring the of cholesterol and for this purpose new techniques are required to integrate the proposed material and to quantify the cholesterol levels from the blood veins in order to avoid the cardiovascular diseases.

10. The authors did not discuss anything about fouling. I am expecting that there would be electrode fouling while analyzing these analytes.

Ans. The storage study was conducted and we have observed that sensor is applicable even after the [period of 4 weeks and repeatability test was also done, both experiments suggested that there is less likely chance of fouling sensor. At the same time, we have stated that the proper storage after the use can avoid the fouling of sensor. This is added in the revised version of manuscript.

11. The comparison table is essential to this work in order to describe the efficiency of the proposed sensor with other works. The author should give a comparison table in the revised manuscript.

Ans. In the revised version of manuscript, the comparative table is added with Table 4 and the performance evaluation is discussed before the conclusion section. The performance evaluation of cholesterol oxidase immobilized Co₃O₄ nanocrystals based cholesterol biosensor was compared with the well-established methods using enzymatic approach in the existing literature as given in Table 4. It is obvious from the Table 4 that different materials have been used for the cholesterol detection [35, 42-46]. The presented approach based on cholesterol oxidase immobilized Co₃O₄ nanocrystals is simple, accurate, sensitive and cost-effective and more likely has high potential to quantify the cholesterol under the biological matrix.  Importantly, the proposed method has capability to evaluate higher cholesterol levels from  the real samples and can used as an alternative method for the wide range of clinical and biomedical applications.  

12. The typos and grammatical errors are scattered throughout the paper and must be corrected with the utmost care.

Ans. In the revised version of manuscript the elimination of typo and grammar mistakes were proofread.

 

Round 2

Reviewer 1 Report

The current revised version of the paper is much improved with all comments being implemented. I therefore, recommend publication.

Reviewer 2 Report

Authors have performed the revision in perfect manner. So, I strongly recommend for publication.