Structural Colors Based on Amorphous Arrays Comprised Solely of Silica Particles
Round 1
Reviewer 1 Report
The authors described a simple method for the fabrication of atypical silica particles with structural colors. This paper is well-organized and experimental results are convincing. I suggest the authors amend the following issues before its acceptance.
Too many grammar errors. I strongly suggest the authors to find a native English speaker to check your manuscript. Herein, I list some of the errors:
Line 14, “And then the characteristics of” —> “Then the characteristics of”
Line 16, ”All the silica powders is obtained a structural color” —> ”All the silica powders obtained structural colors”
Line 17-19, “It is confirmed that the structural color using solely of silica particles has different colors depending on the size of the silica particles, and is highly independent according to the angle change.” —> “It is confirmed that the silica particles show different sturctural colors depending on the size of the particles, and it is highly independent to the viewing angle.”
Line 50, “monodisperse spherical” —> “monodispersed spherical”
Line 53, “And Gokhan topcu et al.” —> “Gokhan topcu et al.”
Line 59, “a simple method of fabricating structural color with low angle-dependence are proposed” —> “a simple method for fabricating structural color with low angle-dependence is proposed”
Line 61-62, revise this sentence “Silica powders are dried through the convection oven that produces various angle-independent colors according to the particle size such as blue, green and red.”
Line 103, “And the size of spherical silica nanoparticles is 455 nm.” —> “The average size of spherical silica nanoparticles is 455 nm.”
Line 107, “This small silica particles have a spherical or atypical form.“ —> “These small silica particles show spherical or atypical forms.“
Line 136-147, ”homogeneously sized monodisperse spherical silica nanoparticles.“ —> ”homogeneously sized, monodispersed spherical silica nanoparticles.“
Line 154, “the size of spherical silica nanoparticles is 455 nm,” —> “the average size of spherical silica nanoparticles is 455 nm,”
Figure 4 shows the SEM images of silica powders. However, the atypical silica particles are very rare from the fabricated powder sample. Thus, it’s not very convincing to me that “While atypical silica particles make the structural colors, and the fabricated particles sizes are 115, 145, and 265 nm in the case 2-4.” I suggest the authors to measure the size distribution of silica in solution using dynamic light scatter (DLS) if possible, and provide a DLS size distribution figure in the revised manuscript. Delete Figure 5. The size values are given in the context, it’s unnecessary to plot these values in a figure. In addition, the error bars in Figure 5 are doubtful. In the introduction section, I suggest the authors to add 2-4 sentences the emphasis the applications of this technology (atypical silica particles with structural colors).
Author Response
December 19, 2019
Dear Editor of Applied Sciences
Thanks a lot for comments on applsci-669778.
Authors completely improve the quality of this work based on not only the reviewer’s valuable suggestions but also check again all portions of the manuscript.
Then, “response to reviewer’s comments” are summarized points by points, and authors improved the original version as indicated in red.
For more comments or questions on this manuscript, do not hesitate to contact us.
Thank you once again.
Professor Chang-Yull Lee
Department of Aerospace Engineering,
Chosun University, South Korea
Response to Reviewer 1 Comments
Thanks for valuable suggestions to improve the quality of the manuscript.
The authors described a simple method for the fabrication of atypical silica particles with structural colors. This paper is well-organized and experimental results are convincing. I suggest the authors amend the following issues before its acceptance.
Point 1: Too many grammar errors. I strongly suggest the authors to find a native English speaker to check your manuscript. I list some of the errors:
Line 14, “And then the characteristics of” —> “Then the characteristics of”
Line 16, “All the silica powders is obtained a structural color” —> “All the silica powders obtained structural colors”
Line 17-19, “It is confirmed that the structural color using solely of silica particles has different colors depending on the size of the silica particles, and is highly independent according to the angle change.” —> “It is confirmed that the silica particles show different sturctural colors depending on the size of the particles, and it is highly independent to the viewing angle.”
Line 50, “monodisperse spherical” —> “monodispersed spherical”
Line 53, “And Gokhan topcu et al.” —> “Gokhan topcu et al.”
Line 59, “a simple method of fabricating structural color with low angle-dependence are proposed” —> “a simple method for fabricating structural color with low angle-dependence is proposed”
Line 61-62, revise this sentence “Silica powders are dried through the convection oven that produces various angle-independent colors according to the particle size such as blue, green and red.”
Line 103, “And the size of spherical silica nanoparticles is 455 nm.” —> “The average size of spherical silica nanoparticles is 455 nm.”
Line 107, “This small silica particles have a spherical or atypical form.” —> “These small silica particles show spherical or atypical forms.”
Line 136-147, “homogeneously sized monodisperse spherical silica nanoparticles.” —> “homogeneously sized, monodispersed spherical silica nanoparticles.”
Line 154, “the size of spherical silica nanoparticles is 455 nm,” —> “the average size of spherical silica nanoparticles is 455 nm,”
Response 1: Thank you so much for your kind review. Author corrected the sentences pointed out by the reviewer. According to the reviewer’s comment, the manuscript was checked again by native speakers. We would like to thank Editage (www.editage.co.kr) for English language editing.
Point 2: Figure 4 shows the SEM images of silica powders. However, the atypical silica particles are very rare from the fabricated powder sample. Thus, it’s not very convincing to me that “While atypical silica particles make the structural colors, and the fabricated particles sizes are 115, 145, and 265 nm in the case 2-4.” I suggest the authors to measure the size distribution of silica in solution using dynamic light scatter (DLS) if possible, and provide a DLS size distribution figure in the revised manuscript. Delete Figure 5. The size values are given in the context, it’s unnecessary to plot these values in a figure. In addition, the error bars in Figure 5 are doubtful.
Response 2: Thanks for your advice. The particle size of each sample was measured using the nano-micro particle size analyzer (PSA, Scatteroscope-І, Qudix). Additionally, author modified Figure. 5, and revise the manuscript as follows:
”Figure 4 presents SEM images of the silica powder. Figure 4 (a) shows a silica powder synthesized without the phenol-formaldehyde resin, and the silica particles show uniform spherical shapes and sizes. On the other hand, the silica powders in Figures 4 (b-d) are synthesized with phenol-formaldehyde resin. Spherical or atypical particles are formed. Unlike Figure 4 (a), some necks are observed between the nanoparticles. This result is due to the phenol-formaldehyde resin.
Figure 5 indicates the particle size distribution of the manufactured silica powders. Each silica powder is mixed with DI water at a concentration of 0.01 g/mL to determine the size of the particles. Subsequently, the mixture is ground in an ultrasonicator for 15 min. Next, the size of the silica particles is measured using a nano-micro particles size analyzer. The average size of the spherical silica nanoparticles without the phenol-formaldehyde resin is 435 nm (Case 1). While the average size of nanoparticles with the phenol-formaldehyde resin is 359 nm, 375 nm and 502 nm, respectively (Case 2–4). Consequently, the average size of silica nanoparticles increases with increasing phenol-formaldehyde resin content.”
Point 3: In the introduction section, I suggest the authors to add 2-4 sentences the emphasis the applications of this technology (atypical silica particles with structural colors).
Response 3: Thanks for your comments. Author added some sentences on the applications of this technology (atypical silica particles with structural colors) in the introduction section.
“These characteristics can increase the energy efficiency of solar cells and can be used in paint or cosmetic materials with super-hydrophobicity and high sustainability.”
Thank you again.
If you have additional comments or questions for this manuscript, do not hesitate to inform authors as soon as possible.
Best regards,
Chang-Yull Lee
Author Response File: 
Author Response.docx
Reviewer 2 Report
Lee and co-workers present a method to prepare amorphous arrays of silica particles. The deposition leads to a structure-based colour impression. The addition of a phenol-formaldehyde resin is supposed to stabilize the amorphous structure to create an easy way of fabrication. The silica films are supposed to have a colour impression independent of the angle of observation.
The study itself is of very little content. The influence of the colour of a colloidal film (crystalline or amorphous) and that additives can influence this, is well known. Furthermore, the authors fail to describe their method of measuring a particle size distribution. It is unclear to the reader if the mentioned particle sized is based on measuring the particles by the SEM images or if another technique is applied. Furthermore, the colour impression is solely stated by an optical camera. Absorption/reflection measurements would enable a better understanding of the optical properties. Furthermore, characterization fundamentals and details (utilized instruments, e.g. XRD, SEM and the camera; purity and suppliers of the chemicals; measurement angles of the optical colour impression) are missing. The colloidal films are of very poor quality. It is obvious that they are not even constant in the film thickness which makes a measurement of the optical qualities (which is missing in the study anyway) impossible.
The authors claim to present a one-step synthesis protocol to fabricate an amorphous array of silica particles, but neither the pristine silica particle nor the atypical silica particle synthesis protocol consists of one step (see Figure 1 and text ll. 70-80):
mixing reagents adjusting pH drying grinding dispersing in solvent poring over a glass slide23: the first sentence of the introduction does not make much sense to me.
Figure 3: How do the XRD measurements support that the synthesized material is SiO2?
Figures 4 and 5: How was the particle size determined? Please add a measurement of the particle size distribution
Figure 8: The figure caption mentions that the pictures were taken at three different viewing angles. Unfortunately, it is not mentioned which angles were investigated.
The authors should consult a native speaker to improve the language quality of the manuscript.
The manuscript lacks in content, scientific soundness and interpretation of the (few) data. Therefore, I cannot recommend to accept the study for publication in Appl. Sci.
Author Response
December 19, 2019
Dear Editor of Applied Sciences
Thanks a lot for comments on applsci-669778.
Authors completely improve the quality of this work based on not only the reviewer’s valuable suggestions but also check again all portions of the manuscript.
Then, “response to reviewer’s comments” are summarized points by points, and authors improved the original version as indicated in red.
For more comments or questions on this manuscript, do not hesitate to contact us.
Thank you once again.
Professor Chang-Yull Lee
Department of Aerospace Engineering,
Chosun University, South Korea
Response to Reviewer 2 Comments
Thanks for valuable suggestions to improve the quality of the manuscript.
Lee and co-workers present a method to prepare amorphous arrays of silica particles. The deposition leads to a structure-based colour impression. The addition of a phenol-formaldehyde resin is supposed to stabilize the amorphous structure to create an easy way of fabrication. The silica films are supposed to have a colour impression independent of the angle of observation.
The study itself is of very little content. The influence of the colour of a colloidal film (crystalline or amorphous) and that additives can influence this, is well known.
Point 1: Furthermore, the authors fail to describe their method of measuring a particle size distribution. It is unclear to the reader if the mentioned particle sized is based on measuring the particles by the SEM images or if another technique is applied.
Response 1: Thanks for your advice. The particle size of each sample was measured using the nano-micro particle size analyzer (PSA, Scatteroscope-І, Qudix). Additionally, author modified Figure. 5, and revise the manuscript as follows:
”Figure 4 presents SEM images of the silica powder. Figure 4 (a) shows a silica powder synthesized without the phenol-formaldehyde resin, and the silica particles show uniform spherical shapes and sizes. On the other hand, the silica powders in Figures 4 (b-d) are synthesized with phenol-formaldehyde resin. Spherical or atypical particles are formed. Unlike Figure 4 (a), some necks are observed between the nanoparticles. This result is due to the phenol-formaldehyde resin.
Figure 5 indicates the particle size distribution of the manufactured silica powders. Each silica powder is mixed with DI water at a concentration of 0.01 g/mL to determine the size of the particles. Subsequently, the mixture is ground in an ultrasonicator for 15 min. Next, the size of the silica particles is measured using a nano-micro particles size analyzer. The average size of the spherical silica nanoparticles without the phenol-formaldehyde resin is 435 nm (Case 1). While the average size of nanoparticles with the phenol-formaldehyde resin is 359 nm, 375 nm and 502 nm, respectively (Case 2–4). Consequently, the average size of silica nanoparticles increases with increasing phenol-formaldehyde resin content.”
In addition, author has added to the some sentences about the measurements and materials used in the experimental setup.
Point 2: Furthermore, the colour impression is solely stated by an optical camera. Absorption/reflection measurements would enable a better understanding of the optical properties.
Response 2: Thanks for your valuable comment. Authors have prepared a future work on the absorption and reflection of colloidal films using coating methods. At that time, authors will conduct the experiments according to your comment in order to improve the quality of results.
Point 3: Furthermore, characterization fundamentals and details (utilized instruments, e.g. XRD, SEM and the camera; purity and suppliers of the chemicals; measurement angles of the optical colour impression) are missing.
Response 3: Thanks for your advice. Author added the <2.1. Measurements and Materials> section, and added the manuscript about the XRD and SEM equipment and chemicals. Measurement angles are also added.
“2.1. Measurements and Materials
The arrangement and particle shape of the silica particles were monitored using scanning electron microscopy (SEM, S-4800, Hitachi). The product synthesized through the sol-gel process was examined using x-ray diffraction (XRD, X'pert Pro MRD, PANalytical). The size of the silica particles was measured using a nano-micro particle size analyzer (PSA, Scatteroscope-І, Qudix). The reagents used for silica synthesis were deionized (DI) water (extra pure grade, Duksan), ethanol (EtOH, 95%, Duksan), ammonia water (28.0–30.0%, Samchun), tetraethyl orthosilicate (TEOS, 95%, Samchun), and phenol-formaldehyde resin. The phenol-formaldehyde resin was synthesized from phenol (99%, Samchun) and formaldehyde (35%, Samchun) in a ratio of 1: 1.5 [19].”
Point 4: The colloidal films are of very poor quality. It is obvious that they are not even constant in the film thickness which makes a measurement of the optical qualities (which is missing in the study anyway) impossible.
Response 4: Authors are sorry for the somewhat poor quality of the colloidal films. However authors focused on the results of the structural color highly independent on the viewing angles. In addition, a simple process was presented compared to the conventional complex manufacturing methods. In future works, authors will show an improved results. Thanks again for your advice.
Point 5: The authors claim to present a one-step synthesis protocol to fabricate an amorphous array of silica particles, but neither the pristine silica particle nor the atypical silica particle synthesis protocol consists of one step (see Figure 1 and text ll. 70-80): mixing reagents adjusting pH drying grinding dispersing in solvent poring over a glass slide.
Response 5: In past research, after colloidal silica was synthesized, silica particles were obtained using a centrifugal separator. Secondary particles were added to the silica particles to induce an amorphous array. There are several steps. In this paper, phenol-formaldehyde resin was added in the Sol-Gel process to synthesize colloidal silica to induce amorphous array. Therefore, authors described it as a one-step process because it is manufactured in an easy and very simple way. Thank you again.
Point 6: 23: the first sentence of the introduction does not make much sense to me.
Response 6: The author revised the first sentence according to the reviewer’s comment. Thank you for your advice.
“Generally, the color of a substance is determined by its dyestuff and pigment. However, the colors of these chemicals can degrade after prolonged exposure to ultraviolet radiation, which can lead to environmental pollution and product cost issues.”
Point 7: Figure 3: How do the XRD measurements support that the synthesized material is SiO2?
Response 7: Based on the XRD results, authors added 2 references that can determine that the synthesized material is SiO2. Authors also added some sentences by comparing the results with the SiO2 pattern in data from (Card No. 96-901-3492) of the Crystallography Open Database (COD).
“No additional peaks are found in other regions. The trend for these XRD patterns is the same as that for the silica obtained by the sol-gel process reported by Lin et al. [20]. The measured pattern (88%) is consistent with the SiO2 pattern reported in the crystallography open database (COD, no. 96-901-3492) [21]. We can thus confirm that the material produced by this method is SiO2.”
Point 8: Figures 4 and 5: How was the particle size determined? Please add a measurement of the particle size distribution.
Response 8: It seems to be the same comment as Point 1.
The particle size of each sample was measured using the nano-micro particle size analyzer (PSA, Scatteroscope-І, Qudix). Additionally, author modified Figure. 5, and revise the manuscript as follows:
”Figure 4 presents SEM images of the silica powder. Figure 4 (a) shows a silica powder synthesized without the phenol-formaldehyde resin, and the silica particles show uniform spherical shapes and sizes. On the other hand, the silica powders in Figures 4 (b-d) are synthesized with phenol-formaldehyde resin. Spherical or atypical particles are formed. Unlike Figure 4 (a), some necks are observed between the nanoparticles. This result is due to the phenol-formaldehyde resin.
Figure 5 indicates the particle size distribution of the manufactured silica powders. Each silica powder is mixed with DI water at a concentration of 0.01 g/mL to determine the size of the particles. Subsequently, the mixture is ground in an ultrasonicator for 15 min. Next, the size of the silica particles is measured using a nano-micro particles size analyzer. The average size of the spherical silica nanoparticles without the phenol-formaldehyde resin is 435 nm (Case 1). While the average size of nanoparticles with the phenol-formaldehyde resin is 359 nm, 375 nm and 502 nm, respectively (Case 2–4). Consequently, the average size of silica nanoparticles increases with increasing phenol-formaldehyde resin content.”
In addition, author has added to the some sentences about the measurements and materials used in the experimental setup.
Point 9: Figure 8: The figure caption mentions that the pictures were taken at three different viewing angles. Unfortunately, it is not mentioned which angles were investigated.
Response 9: Thanks for your comment. The authors indicated the viewing angles in figure 8 and the text.
Point 10: The authors should consult a native speaker to improve the language quality of the manuscript.
Response 10: Thanks for your advice.
According to the reviewer’s comment, the manuscript was checked again by native speakers. We would like to thank Editage (www.editage.co.kr) for English language editing.
Thank you again.
If you have additional comments or questions for this manuscript, do not hesitate to inform authors as soon as possible.
Best regards,
Chang-Yull Lee
Author Response File: Author Response.docx
Reviewer 3 Report
Experimental procedures need to be explained in detail (e.g. materials, equipments, etc.).
There are numerous grammatical errors. Please go over the manuscript and correct them.
Author Response
December 19, 2019
Dear Editor of Applied Sciences
Thanks a lot for comments on applsci-669778.
Authors completely improve the quality of this work based on not only the reviewer’s valuable suggestions but also check again all portions of the manuscript.
Then, “response to reviewer’s comments” are summarized points by points, and authors improved the original version as indicated in red.
For more comments or questions on this manuscript, do not hesitate to contact us.
Thank you once again.
Professor Chang-Yull Lee
Department of Aerospace Engineering,
Chosun University, South Korea
Response to Reviewer 3 Comments
Thanks for valuable suggestions to improve the quality of the manuscript.
Point 1: Experimental procedures need to be explained in detail (e.g. materials, equipments, etc.).
Response 1: Thanks for your valuable advice.
Author has added to the some sentences about the measurements and materials used in the experimental setup. In addition, some comments have been added to several parts in the paper.
“The arrangement and particle shape of the silica particles were monitored using scanning electron microscopy (SEM, S-4800, Hitachi). The product synthesized through the sol-gel process was examined using x-ray diffraction (XRD, X'pert Pro MRD, PANalytical). The size of the silica particles was measured using a nano-micro particle size analyzer (PSA, Scatteroscope-І, Qudix). The reagents used for silica synthesis were deionized (DI) water (extra pure grade, Duksan), ethanol (EtOH, 95%, Duksan), ammonia water (28.0–30.0%, Samchun), tetraethyl orthosilicate (TEOS, 95%, Samchun) and phenol-formaldehyde resin. The phenol-formaldehyde resin was synthesized from phenol (99%, Samchun) and formaldehyde (35%, Samchun) in a ratio of 1: 1.5 [19].”
Point 2: There are numerous grammatical errors. Please go over the manuscript and correct them.
Response 2: Thanks for your advice.
According to the reviewer’s comment, the manuscript was checked again by native speakers. We would like to thank Editage (www.editage.co.kr) for English language editing.
Thank you again.
If you have additional comments or questions for this manuscript, do not hesitate to inform authors as soon as possible.
Best regards,
Chang-Yull Lee
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have taken care of my previous comments in great detail. Thus, I suggest its acceptance.
