Polydopamine-Mediated Ag and ZnO as an Active and Recyclable SERS Substrate for Rhodamine B with Significantly Improved Enhancement Factor and Efficient Photocatalytic Degradation

Round 1

Reviewer 1 Report

In the present work, the authors describe a methodology for obtaining a SERS material based on a hierarchical architecture of Ag Nps attached to ZnO rod-like nanostructures deposited on a GMF substrate. For improving both the fabrication and the electronic properties of the final material, the authors include a PDA layer, which is supposed to provide such improvements thanks to its adhesive properties along with charge transfer and distribution capabilities.

The presentation and discussion of the results is clear and easily understandable. Nevertheless, I suggest a few minor revisions before publication:

1. English writing should be reviewed; some typos and style problems are present in the manuscript.
2. Since the authors do not perform an extensive study regarding the properties of PDA, references regarding its adhesive and electronic properties should be included in the Introduction section (page 2, paragraph from line 58 to 64) and the Results section (page 6, lines 219-222).
3. Page 5, line 194: the authors state that “In general, the electrons within solid materials need more energy relative to the vacuum level especially to cross the lattice adsorption force to become free electrons.” Please, provide references.
4. Regarding Ag Nps in Figure A2, is it possible to mark them with an arrow for a clearer and faster understanding of their location?
5. Ag Nps have been reported to be 28 nm. I supposed that the authors have used a manual counting technique using the SEM images but, which pictures have they used? Which magnification? Is it described in Materials and Methods? If not, please include.
6. Paragraph 241-243 in page 8 is confusing. Wrong connector used?
7. Some figures and tables are cited after they appear in the text. In my honest opinion, I think it’s clearer when the citation is prior to the Figure/Table.
8. Table 2 has been wrongly named “Table 1”.
9. Finally, there’s a mistake in the Conclusions section: Ag/PDA/CuO@GMF.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Chin and et al, have investigated the SERS enhancement of Rhohamine B using ploydopamine-mediated Ag and Zno. The manuscript is organized and reads well. There are a few correction/issues that need to be address before suggesting for publication.

• “Additionally, a short-range chemical effect, i.e., charge transfer (CT) induced by the presence of a semiconductor (metal oxides) is known to have a significant contribution towards SERS signal enhancement.” Please add citation to this statement (e.g. 10.1039/C9NH00590K)
• Non-metallic SERS-active NPs cab also be added to this list in this sentence “Several efforts have been made to construct a SERS substrate with MNPs and metal-oxide semiconductor such as ZnO, CuO, Cu2O, and TiO2.[3-6]” Please add citation to this statement (e.g. doi.org/10.1016/j.snb.2020.128703)
• The reasons why the ZnO nanostructure has been deposited with Ag is not justified, as ZnO nanostructure can significantly enhance the Raman signal. As presented in this work; doi.org/10.1038/s41467-018-05237-x
• Would be great if the authors could demonstrate the SERS enhancement at different wavelengths.
• For proof of SERS enhancement via charge transfer, it is recommended to use at least two different dyes.
• 2, The broad XPS spectrum needs to be provided.
• The limit of detection should be calculated.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf