Round 1

Reviewer 1 Report

Review of the manuscript entitled ‘SORS performance of sublayer materials with different optical 2 properties under diffuse scattering media’ by Nian Yu et al. In this paper, the authors evaluate the spatially offset Raman spectroscopy (SORS) method in recording the Raman spectra of materials with different optical properties covered with a diffuse scattering barrier.

The research presented is interesting and valuable. The manuscript is suitable for publication and only requires minor revision:

1. Figure 1 should be included in the manuscript.

 

Author Response

Dear reviewer:

We are really appreciative of your comments. We have made some modifications to improve the quality of our manuscript. And we have added the missing Figure 1, thanks again for your kind suggestion.

Reviewer 2 Report

Referee’s report on the paper:

SORS performance of sublayer materials with different optical 2 properties under diffuse scattering media

by Nian Yu, Lili Zhang, Xianbiao Zhang, Chunrui Hu and Chang Chen

submitted to Photonics

General comments

The paper deals with investigations on the dependence of SORS (Spatial Offset Raman Spectroscopy) signals on surface layer thickness, on offset value and on nature of underlying material.

This subject is potentially of interest for Photonics.

The SORS technique has been devised in 2005 by Pavel Matousek and colleagues and extensively studied since then. Even the aspects analysed in the submitted paper are subject of different published papers (see for example [Spatially Offset Raman Spectroscopy—How Deep? By  Sara Mosca, Priyanka Dey, Marzieh Salimi, Benjamin Gardner, Francesca Palombo, Nick Stone, and Pavel Matousek. Anal. Chem. 2021, 93, 17, 6755–6762]). Therefore, the submitted paper does not result to be particularly innovative. Moreover, some important details and explanations are missing, making some experimental observations partially ineffective.

Here below the Authors can find some recommendations that can help them in reviewing the manuscript.

Detailed comments

1.       English style requires major revisions. In particular the Introduction section has to be extensively revised.

2.       The acronym PTFE is used (line 67) before describing it (the definition is given only at line 77).

3.       In sample description the use of “turbid scattering tape” is cited, but no detailed information is given on it (type and brand name, constituent material, …).

4.       Always in this section the total number of samples prepared and used for experimental tests is not given. Three different underlying materials, but for how many different tape layer thicknesses? Moreover, the sublayer materials are in bulk form or as layers? And, in case, which is their thickness?

5.       Figure 1 is missing.

6.       How many measurements have been carried out for every single combination? I mean, does every point on the graphs of figures 2, 3 and 4 derive from just one single measurement? It should be advisable to use mean values from at least 3 measurements, in particular when from graphs specific theories are derived.

7.       It is unclear how the zero offset is achieved. Which is the size of the optical fibers of the bundle?

8.       Most part of the final considerations are based on some statements that are not reflected in literature references or additional experimental data: lines 171-172 “This extraordinary phenomenon might be attributed to silicon’s high absorption and reflective property, in which a specific offset always corresponds to an optimal depth.” Lines 207-208 “laser photons experience multiple scattering inside PTFE as the high 207 scattering property of it.”. And lines 210-211 “For PMMA, there are much fewer backscattered laser photons as the 210 high transparency property of it".

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors present results studying the effect of overlayer thickness and sub-layer optical properties on the results given by the SORS method in Raman. It is an interesting study and a demonstration of the method, however its usefulness in the emphasised application of "non-invasive transcutaneous detection of substances" I feel is lacking. I would recommend it for publication if the impact of the work can be strengthened and after some consideration to the comments below.

- The manuscript is written to a suitable level, but some grammar can be improved throughout the text

- Figure 1 is entirely missing in the document received for peer-review

- Can the authors comment on the suitability of using tape as a model for human skin? A cursory online search would suggest silicones have similar optical properties and could be a superior choice.

- What about materials used in implants or other transcutaneous devices or substances? I understand that silicon, PMMA and PTFE were chosen as they are very different from one another optically, but does that help in the goal of detecting materials beneath the skin?

- Raman spectrometers are ubiquitous in materials characterisation labs and are generally dedicated instruments with little room for bespoke experiments like these. Is this a technique that can be easily retro-fitted to existing instruments?

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Editors,

the Authors have taken into consideration all my comments, improving the paper quality, that now, I think, can deserve the publication on your journal.

 

Reviewer 3 Report

The authors addressed the concerns of the reviewers.