Cu/Mn Synergy Catalysis-Based Colorimetric Sensor for Visual Detection of Hydroquinone

Round 1

Reviewer 1 Report

Dear Editor of coatings

In the assigned manuscript entitled “Cu/Mn Synergy Catalysis-Based Colorimetric Sensor for Visual Detection of Hydroquinone”, the authors deal with the synthesis and characterization of an artificial enzyme (nanozymes) toward Hydroquinone's indirect colourimetric determination. The manuscript is well-written, the topic is very interesting, and the main goal of the work was accomplished. In this way, I should recommend it for publication after minor revisions:

1) line 85 - correct the term “mangan-based oxides”.

2) line 117 - The authors stated that the BJH method was used to gain information about the pore distribution in the Characterization section. However, Table 1 used the abbreviation of Brunauer, Emmett and Teller (BET). What model was used?

3) The nomenclature presented in line 102 for TMB slightly differs from the one in line 288.

4) I understand the idea of the authors using the colour scheme based on shades of blue in Figure 3a. Nonetheless, as the changes are not straightforward, as shown in Figure 7a, I found it slightly confusing.

5) The authors calculated the nanozyme kinetic parameters using the Lineweaver-Burk plot. What about the catalytic constant and efficiency?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript introduces a novel bimetallic nanozyme-based colorimetric sensor utilizing MnO2@CuAl-CLDHs for the sensitive and visual detection of hydroquinone (HQ) in environmental samples. The approach is innovative, and the manuscript is well-written, though minor revisions to the English are suggested to improve clarity. It is acknowledged that English may not be the first language of the authors. The following comments and suggestions are provided for consideration:

1. 1. Page 2, Lines 49-51: The term "catalyst" should be changed to "catalyze" for grammatical accuracy. Additionally, it would benefit the reader to include references to review articles or specific works on nanozymes and their applications in colorimetric assays, particularly for those unfamiliar with the field.

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3. 2. Page 2, Line 86: The manuscript transitions from using "LDHs" to "CLDHs" without clearly defining the latter. If CLDHs stands for "Cu-based LDHs," this should be explicitly stated, for example, "Cu-based LDHs (CLDHs)." If not, the abbreviation CLDHs needs to be defined.

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5. 3. Page 3, Section 2.1: While the manuscript notes that all reagents were used without further purification, specifying the purity or grade of critical reagents is recommended, as their quality could significantly impact the synthesis or performance of the MnO2@CuAl-CLDHs.

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7. 4. Page 3, Line 128: The conditions of centrifugation used to collect solid products from the hydrothermal reaction, such as speed (or gravity) and duration, should be provided to allow for reproducibility.

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9. 5. Page 6, Lines 231-241: The use of Powder Diffraction File (PDF) numbers is effective for confirming the crystal structure of synthesized materials. A brief explanation of the PDF database and its authority would greatly benefit readers unfamiliar with it.

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11. 6. Page 9, Figures 6a and 6b: The color scheme used in these figures makes it challenging to distinguish between lines, impacting the clarity of presented data. While the chosen colors relate to actual sample color changes, they do not translate well graphically. Clarifying or altering the presentation could improve readability and data interpretation.

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13. 7. Page 12, Lines 431-439 and Figures 7c and 7d: The methodology for testing potential interferents is not clearly described. Details such as the concentration of interferents tested and whether a concentration study was conducted for each interferent, similar to Figure 7b, should be included. Additionally, it should be clarified if tests included samples with both HQ and interferents, and if so, whether the sensor system provided consistent HQ measurements.

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15. 8. Page 13, Table 3: The authors compare their sensor to other HQ sensors from the last 8-10 years, predominantly colorimetric, with one electrochemical and one fluorescent sensor. The introduction mentions various other detection methods for HQ, such as HPLC and atomic absorption spectroscopy. A comparison of the proposed sensor system with these techniques would offer a comprehensive understanding of its advantages and limitations.

9. In general, please balance the chemical equations.

10. Sections 3.1 and 3.2: Overall, these sections are very long which can interfere with reader comprehension, especially those not familiar with all aspects of the work. A possible solution could be to add additional subsections to section 3.1 specifically delineating between the preparation of the MnO2@CuAl-CLDHs and the characterization. This should be considered a suggestion, but it may make these sections flow better.

This reviewer recommends publication following major revisions.

Overall, the quality of the English language is very good, though one final editing to ensure agreement between subjects and verbs as well as tense should be done. However, these small inconsistencies did not detract from the overall presentation of the material.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have addressed all of this reviewer's comments and suggestions. This is a nice manuscript and should be published in its present form. This reviewer would also like to thank the authors for their prompt response and attention to detail.

The authors should perform one final spell check of the paper, but otherwise, this should be accepted.

English style is excellent but one final spell check/editing should be completed.