Synthesis, Characterization, and Electrochemical Evaluation of Copper Sulfide Nanoparticles and Their Application for Non-Enzymatic Glucose Detection in Blood Samples

Round 1

Reviewer 1 Report

This manuscript reports on synthesis and characterization of glutathione capped copper sulfide nanoparticles of two sizes (ca. 4.5 and 25 nm) and their use for nonenzymatic glucose detection. While the study has some value, it appears to be too preliminary and lacking new insight or methods.  Thus, I cannot recommend the publication of the manuscript in its current form.  Specifically:

11)      Over the last ca. 5 years copper sulfide nanostructures (and not only nanotubes mentioned by the authors) have been studied extensively for biosensing applications including glucose detection.  The authors should briefly review the available literature and indicate what kind of questions that are not covered in the available literature they are trying to address in the proposed study.  Basically, what is the novelty of the conducted study?

22)      Electrochemical detection depends on making electrical contacts of the electrode with the nano structures and therefore many recent studies focused on the proper encapsulation of the nano structures and the electrode preparation.  Thus, the main conclusion that the larger 25 nm particles represent better sensors because of better conductivity constitutes a well-established fact and lacks novelty.  The authors should not claim that they observed the size dependence as small particles were non-conductive.  In order to demonstrate the size dependence, the authors  should prepare a series of particles of different sizes including larger than 25 nm.

33)      The rather large variations in performance of different electrodes are related to the issue mentioned above (#2).  While the drop-cast method is simple, it did not result in superior sensor performance as compared with other electrodes based on copper sulfide nanostructures.  There is a concern that the observed variation would prevent the practical applications of the proposed sensor.  

44)      The electrode characterization and comparison of different electrodes was carried out at 10 mM ionic strength and a single glucose concentration (3 mM).  Such a characterization should be extended to at least at two glucose concentration and in a buffer mimicking ionic strength and pH of blood.

55)      My concern is that using just 5 spiked blood samples is statistically insufficient.

66)      Why the horizontal axis for XRD spectra is labeled “Intensity (nm)”?     

Author Response

Revision Document for Reviewer 1 attached

Author Response File: Author Response.docx

Reviewer 2 Report

In this paper, the authors synthesized copper sulfide nanoparticles with different sizes and investigated their application in non-enzymatic glucose detection. This work is interesting, which can be accepted after major revision. Some specific questions are placed in the following.

1. The TEM image of CuS-1 is too fuzzy, which is hard to recognize the average size of 4.5 nm. This should be replaced a clear one.

2. Why a lower bandgap of CuS is farvorable for electrochemical property? The authors should explain the reason.

3.  In Fiugre 2A, CuS-1 exhibits a strong absorption in NIR region and the peak was not completely measured. It's confused to provide the bandgap of 2.09 eV. This mistake should be carefully revised.

4. The layout of figures is ugly. Please rearrange them carefully.  

Author Response

Revisions for Author 2 attached

Author Response File: Author Response.docx

Reviewer 3 Report

See the attachment.

Comments for author File: Comments.pdf

Author Response

Reviewer 3 revisions attached

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

with the changes made this manuscript can be published.

Reviewer 2 Report

The manuscript has been revised accordingly.

Reviewer 3 Report

This manuscript has been revised and improved. Now it can be accepted for publication.