Synthesis and Luminescence Properties of Green-to-Red Color-Tunable Upconverting K2Gd(PO4)(WO4):Yb3+,Tb3+,Eu3+ Phosphors
Round 1
Reviewer 1 Report
Comments
The article describes synthesis and investigation of optical properties of two series of K2Gd(PO4)(WO4):20%Tb3+ (KGPW).
The theme is interesting, although some concerns must be addressed:
- Please try to emphasize the aim and novelty of the study at the end of the ‘Introduction” section.
- All figures must be included after their first mention in the text.
- Please remove the blank line (control paragraph setting) between line 112 and line 113.
- Full information about used instruments (company, city, country) must be provided, as there were provided for all reagents.
- Please remove the blank line (control paragraph setting) between line 140 and line 141.
- Figure 7 caption is way too long. Maybe the explanations can be introduced as a note, a legend in the figure or the main text.
- The English language must be slightly revised.
Author Response
Response to Reviewer 1 Comments
The article describes synthesis and investigation of optical properties of two series of K2Gd(PO4)(WO4):20%Tb3+ (KGPW).
The theme is interesting, although some concerns must be addressed:
Point 1: Please try to emphasize the aim and novelty of the study at the end of the ‘Introduction” section.
Response 1: The novelty and aim of the work were included in the Introduction section.
Point 2: All figures must be included after their first mention in the text.
Response 2: We thank the reviewer for the comment. The final formatting of the manuscript will be performed by the staff of the journal.
Point 3: Please remove the blank line (control paragraph setting) between line 112 and line 113.
Response 3: The line has been removed.
Point 4: Full information about used instruments (company, city, country) must be provided, as there were provided for all reagents.
Response 4: Full information about the instruments was given.
Point 5: Please remove the blank line (control paragraph setting) between line 140 and line 141.
Response 5: The line has been removed.
Point 6: Figure 7 caption is way too long. Maybe the explanations can be introduced as a note, a legend in the figure or the main text.
Response 6: The Figure 7 caption was significantly shortened as the reviewer suggested.
Point 7: The English language must be slightly revised.
Response 7: We thank the reviewer for the remark. The English language was revised using a professional version of Grammarly software.
Reviewer 2 Report
The work is fine but science contained in the paper, though real, is too incremental for the paper to be accepted for publication. As a reviewer, I have a few comments that will allow me to improve the work in the future:
1) The review part should be extended. Please give more information about influence of preparation method on luminescence properties.
2) Please show a photo of the powders in excitation light and white light
3) The particle size of powders should be confirmation by SLS or DLS technique. The relationship between the microstructure and optical properties is necessary to discuss.
4) Schematic energy level diagram of energy transitions (Fig. 1) is rather Jablonski than Dieke`s diagram.
5) Please provide additional information about lasers which were used in experiments.
6 ) How was the luminescence decay time determined? If a standard fit was used, was there only one component?
7) This is not the main goal of the work, but the authors can also determine the band gap energy from diffuse reflectance spectra.
8) I found a few editing errors in the text, it is possible that they were created when generating the PDF. However, I advise you to check the text again.
Author Response
Response to Reviewer 2 Comments
The work is fine but science contained in the paper, though real, is too incremental for the paper to be accepted for publication. As a reviewer, I have a few comments that will allow me to improve the work in the future:
Point 1: The review part should be extended. Please give more information about influence of preparation method on luminescence properties.
Response 1: After the extensive literature review we came to the conclusion that the given material cannot be synthesized by alternative methods, for instance, Pechini sol-gel, or sol-gel combustion because all the papers dealing with such type compounds report solid-state synthesis method. The reason for this could be that rare earth ions in aqueous media start forming insoluble hydroxides at pH ≈ 7. The MoO42− ions, on the other hand, are only stable in alkaline solutions, and H2MoO4 precipitates under acidic conditions. Furthermore, the rare earth ions also instantly react with PO43– ions to yield insoluble REPO4. All these issues combined make it very difficult to prepare such compounds by a wet synthesis method.
Point 2: Please show a photo of the powders in excitation light and white light.
Response 2: We thank the reviewer for the comment. Digital images of the synthesized phosphors at daylight and under 365 nm excitation are provided in Figure S13.
Point 3: The particle size of powders should be confirmation by SLS or DLS technique. The relationship between the microstructure and optical properties is necessary to discuss.
Response 3: We thank the reviewer for the suggestion. We think that the particle size/morphology influence on the optical properties of these materials would be interesting research and we are considering this as a separate study. However, adding such a discussion to the present paper would make it more complicated and harder to follow since there is a lot of information provided already.
Point 4: Schematic energy level diagram of energy transitions (Fig. 1) is rather Jablonski than Dieke`s diagram.
Response 4: We would like kindly disagree with this statement. The energy-level diagram for trivalent lanthanide ions is commonly called the “Dieke diagram” (An Introduction to the Optical Spectroscopy of Inorganic Solids, By Jose Solé, Luisa Bausa, Daniel Jaque, Wiley, 2005). The Jablonski diagram, in turn, illustrates the electronic states and vibrational levels of molecules, and also the transitions between them. Our work deals with trivalent rare earth ions; therefore, in our opinion, using the Dieke diagram is completely fine.
Point 5: Please provide additional information about lasers which were used in experiments.
Response 5: The information on excitation sources was provided in the revised manuscript.
Point 6: How was the luminescence decay time determined? If a standard fit was used, was there only one component?
Response 6: As was mentioned in the text, the effective PL values were calculated from the decay curves using the equation. (see PDF )
All fits were mono-exponential, except decay curves monitored at 542 nm for 340 nm excitation.
Point 7: This is not the main goal of the work, but the authors can also determine the band gap energy from diffuse reflectance spectra.
Response 7: The bandgap energy (3.8 eV) of KGPWO host material was calculated as the reviewer suggested.
Point 8: I found a few editing errors in the text, it is possible that they were created when generating the PDF. However, I advise you to check the text again.
Response 8: We thank the reviewer for the remark. The editing errors were corrected.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
I read the contribution of Julija Grigorjevaite and Arturas Katelnikovas with interest. The paper discussed the synthesis and investigation of the optical properties of two series luminescent materials. The manuscript is well organized. The abstract covers most information of the work and introduction cover the manuscript subject. It is a completed work using different advanced tools for structure elucidation and application. I think it would be interesting for the readers. It fits the target of the journal and therefore I recommend for publication after minor revision.
Comments
1. English should be revised in the whole manuscript
2. L 18 and 19 should be rewritten
3. L 57-62 should be supported by references
4. L 64 should be added by reference
5. Figure 3, 5 and 6, the authors should remove the overlapping of the spectra.
6. More emphasis on finding and its implication may be mentioned in the conclusion section.
Author Response
Response to Reviewer 3 Comments
This is a well prepared manuscript. Following are my comments that in my point of view could improve the manuscript.
Point 1: Please check the energy diagram of Eu3+ in figure 1. Has the yellow line the same nanometers as the orange line?
Response 1: We thank the reviewer for the remark. Figure 1 was corrected.
Point 2: Please consider performing a data fit to the data of graphs 7c and 7f, 8b and 8c, 9b and 9c to determine mathematically the tendency of the curve.
Response 2: We thank the reviewer for the remark. The lines in Figure 7c, 7f, 8b, 8c, 9b, and 9c have been changed using exponential fit. The tendency of the curves showed that decay and rise times decrease exponentially.
Point 3: Please add and comment the following related reference
Xiaoyong Huang et al. https://doi.org/10.1016/j.ceramint.2017.05.123
Response 3: The suggested reference was added to the manuscript.
Point 4: The authors have also two very new publications in mdpi journal regarding upconversion with K2Gd(PO4)(WO4) as a host
Materials 2023, 16(3), 1305; https://doi.org/10.3390/ma16031305
Materials 2023, 16(3), 917; https://doi.org/10.3390/ma16030917
Please add them in the reference list and discuss their differences with the current work and how Eu3+ changes the results of the above references.
Response 4: The suggested references were added and briefly discussed.
Author Response File: Author Response.pdf
Reviewer 4 Report
Dear authors
This is a well prepared manuscript. Following are my comments that in my point of view could improve the manuscript.
Comment 1
Please check the energy diagram of Eu3+ in figure 1. Has the yellow line the same nanometers as the orange line?
Comment 2
Please consider performing a data fit to the data of graphs 7c and 7f, 8b and 8c, 9b and 9c to determine mathematically the tendency of the curve.
Comment 3
Please add and comment the following related reference
Xiaoyong Huang e al https://doi.org/10.1016/j.ceramint.2017.05.123
Comment 4
The authors have also two very new publications in mdpi journal regarding upconversion with K2Gd(PO4)(WO4) as a host
Materials 2023, 16(3), 1305; https://doi.org/10.3390/ma16031305
Materials 2023, 16(3), 917; https://doi.org/10.3390/ma16030917
Please add them in the reference list and discuss their differences with the current work and how Eu3+ changes the results of the above references
with kind regards
Author Response
Response to Reviewer 4 Comments
I read the contribution of Julija Grigorjevaite and Arturas Katelnikovas with interest. The paper discussed the synthesis and investigation of the optical properties of two series luminescent materials. The manuscript is well organized. The abstract covers most information of the work and introduction cover the manuscript subject. It is a completed work using different advanced tools for structure elucidation and application. I think it would be interesting for the readers. It fits the target of the journal and therefore I recommend for publication after minor revision.
Point 1: English should be revised in the whole manuscript.
Response 1: Thank you for the comment. The English language was corrected with the professional version of Grammarly software.
Point 2: L 18 and 19 should be rewritten
Response 2: Thank you for the comment. The sentence was rewritten.
Point 3: L 57-62 should be supported by references
Response 3: Thank you for the comment. Few references were added.
Point 4: L 64 should be added by reference
Response 4: Thank you for the comment. Few references were added.
Point 5: Figure 3, 5 and 6, the authors should remove the overlapping of the spectra.
Response 5: We have modified Figure 3 as the reviewer suggested. However, we have left Figures 5 and 6 in their original version since it is easier to observe the changes between emission line intensities.
Point 6: More emphasis on finding and its implication may be mentioned in the conclusion section.
Response 6: The conclusion part was extended.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Now, the manuscript can be accepted.
