Photocatalytic Activities of PET Filaments Deposited with N-Doped TiO₂ Nanoparticles Sensitized with Disperse Blue Dyes

Round 1

Reviewer 1 Report

This paper deals with the development of composite PET-TiO₂-based photocatalytic materials for organic pollution degradation in water. There are numerous characterizations, the paper is well organized. It fits the scope of Catalysts. I recommended this publication after some minor corrections:

-The acronyms need to be detailed on the first time used, as example, PL line 148, DRS line 188, EDTA,TBA, BQ line 1301, … because there are detailed only in the last section (experimental section).

-In the introduction, you mentioned that “water insoluble dyes have rarely been used to sensitize TiO2”, but sensitization with porphyrin dye which is water insoluble is reported see in:

1. Tasseroul et al. Applied Catalysis B: Environmental 182 (2016) 405–413
2. Mahy et al. Journal of Photochemistry & Photobiology A: Chemistry 373 (2019) 66–76
3. Tasseroul et al. Journal of Photochemistry and Photobiology A: Chemistry 272 (2013) 90– 9

It should be mentioned.

-It will be nice to have a comparison with literature concerning the MB degradation and/or comparison with a commercial product as P25 to highlight the efficiency of your materials

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript ID: catalysts-796601

Title: Photocatalytic Properties of Polyethylene Terephthalate Filaments Coated with N-Doped TiO2 Nanoparticles Sensitized with Aqueous Insoluble Disperse Blue Dye

Summary:

The paper studied the photocatalytic properties of PET filaments coated with N-doped TiO2 sensitized or not with a water-insoluble dye, i.e. blue SE–2R. This latter plays different roles in the photocatalytic activity comparing UV and visible light irradiation. Samples have been characterized by FESEM, XRD, XPS, DRS, and also steady-state and time resolved photoluminescence to study the separation efficiency of photo-generated electron-hole pairs. Trapping experiments under UV and visible light were also performed.

General comments:

Synthesis and characterization analyses are presented and described accurately, but some paragraphs are rather difficult to read. There are some points which must be clarified. Abstract and conclusion are to rewrite including results, aim, sense of the work.

I guess this paper can be published, because is dense of accurate information, but some minor revisions are needful. My related comments and questions are reported below, organized following paper sections.

Title: too long. I suggest to shorten it.

Abstract:

• the aim of the research is difficult to understand. Which is the problem to solve, or which is the lack in literature is unclear. Specify already in the abstract the importance of the research work.
• the abstract is presented as a list of what has been done: “SE-2R plays different roles”, which ones? Why and what are such differences?
• “dye-sensitized N-doped TiO2” is repeated many times. The text appears rather heavy.
• Higher adsorption capacity and high separation efficiency have been proved by which characterization analysis?
• How the band gap is influenced by the wavelength of irradiation? Some findings and results should be put already in the abstract.
• In this form the abstract is feeble: it does not report clear information but only what the paper reports.

Introduction:

• The first 4-5 lines of the introduction are very generic and of little content.
• About ref 9: add more information about.
• Lines 65-66: it’s true. But there is a recent publication that maybe should be taken into account. Here the reference: Arabian Journal of Chemistry (2020) 13, 3633–3638
• Line 80: why?
• Lines 86-87: more effective than? what about the comparison with a “classical” (maybe water-soluble) dye-sensitized TiO2?

Results and discussion:

• Add a space between line 120-121
• Pictures: very difficult to read in that format. I suggest to avoid collection of images.
• Lines 207-208: explain better why the positive slope is related to n-type semiconductors.
• 4: absolutely unclear and difficult to read. Improve it.
• Line 231: “slightly greater” is not a good scientific term. Explain better the point related to the “larger band gap”.
• Lines 245-252: a crucial point is that the samples behave differently under UV and visible light irradiation. Why? This is to explain well already at this point of the text.
• Again, many paragraphs are very dense and confused. Try to lighten the sentences; the presentation of the results should be clearer.
• The image of the powders, before and after calcination, is useless.
• Line 286-288: is there a picture reporting the curves of the consecutive runs? Maybe yes but it is reported after. Figures must be reorganized, maybe selecting only the most important.
• Durability is related to the use of a insoluble dye?
• 7: also this figure is too dense and difficult to consult.
• Lines 396-398: the blue SE-2R has a positive and negative role. To explain. A “last sentence” like this is useless.

Conclusions:

Conclusions are more or less the same of what is reported in the abstract. Impossible to find clearly what are the most important findings and results or this paper. “SE-2R played different roles”, which roles?

Moreover, conclusions are too long. They should not be the list of what you have done.

Also in line 545: “were disclosed in the photocatalytic experiments”, it must be explained.

Rewrite conclusion including the most important findings, results, even numbers if important.

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

 

This paper describes the preparation, characterization and the assessment of photocatalytic properties of some PET filaments coated with N‐doped TiO₂ nanoparticles sensitized with disperse blue dye. The achieved materials were thoroughly characterized, by numerous methods in order to highlight their significant properties. Although, a major disadvantage of this article are the long and twisted sentences, which make it difficult to read. A language check as well as a clarification of the explanations is necessary.

A second query is related to the band gap values. As the authors (lines 225-227) and the literature data sustain, o good photocatalytic activity (especially in the visible domain) is related to a decrease of band gap value for TiO₂ NPs, reason for that “TiO₂ has been modified in many different ways through chemical and physical modifications, where the former involves doping, composite formation, defects creation, functionalization, plasmonic sensitization, co-catalyst loading, etc., and the other involves size, morphology, and shape modifications” (Catalysts 2019, 9, 680). Also, the “UV rays possess higher energy than visible light” (line 221). However, in your case, the band gap is increased by modification and k values are comparable or even higher (for S2–F) under visible light irradiation. Please explain. A comparison with similar systems from literature would be helpful.

Why the degradation rates for TiO₂ powders are lower than for the filaments? You did not mention the amount of particles that you have used in the photodegradation experiments.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf