Suitability of title:
The abstract mentioned ZnO nanoparticles stabilized with gum arabic. It is suggested to state this in the title to differentiate this work’s ZnO from other ZnOs.
I had changed the title to ; Line 1 and 2
Microwave-assisted synthesis of ZnO
nanoparticles stabilized with gum arabic: Effect of microwave irradiation time on ZnO
nanoparticles size and morphology.
Abstract
The objective of the work (suppose investigating the effect of irradiation time towards ZnO morphology) is not clearly stated in the abstract.
I had written it clearly the objective of this paper;
Line 17 and 18
The objective of this work is to investigate the effect of irradiation time towards ZnO
nanoparticles morphology and size.
Line 8: Microwave irradiation time at 2 minutes was selected as the best microwave irradiation time… Why is this 2 minutes chosen as the best irradiation time? State
Line 28 and 29
Microwave irradiation time at 2 minutes was selected as the best microwave irradiation time for smallest ZnO nanoparticles averaging about 168 nm sizes based on DLS analysis.
Line 8: Microwave irradiation time at 2 minutes was selected as the best microwave irradiation time… A single sentence of 3 lines is too long. This sentence is one of the results and should be placed after the methodology in the abstract
Line 28 and 29
I had put this sentence after the methodology of the abstract.
Line 13: UV-vis absorption spectra were found in the range of 350 nm… What can be concluded from this value? State.
UV-vis absorption spectrum was found in the range of 350 nm indicating the absorption peak of ZnO nanoparticles.
Line 13 and Line 14: FTIR spectra showed peaks range from 424 to 475 cm-1 which indicated standard peak of ZnO
nanoparticles. The presence of (100), (002) and (101) planes were apparent in the XRD result, indicating the formation of ZnO nanoparticles. FTIR and XRD could not be associated with morphology and the size of the particles, yet bonding and crystalline phases, respectively.
Line 24-26
I had corrected it. FTIR and XRD for indicating standard of Zn–O stretching and crystalline phases, respectively.
Line 16: FESEM image showed spherical morphology controlled growth of aggregates ZnO nanoparticles was achieved by
microwave irradiation and gum arabic as stabilizing and capping agent. This result is related to the objective of this work (effect of
I had removed this sentence.
irradiation time).
The effect of irradiation time has not been discussed in the abstract.
I had discussed it in line 27, 28
The increase in the microwave irradiation time affected the processes of nucleation and crystal growth promoted larger ZnO nanoparticles size Problem statement and review on past
research:
Problem statement that leads to the objective of this work is not clear.
Lack of literature study that supports the effect of irradiation time as the main parameter chosen in this work
My problem statement is
Several synthesis method for nanoparticles required intensive energy consumption and generation of hazardous substances. In my study I used microwave-assisted synthesis that required just a few minutes to synthesis ZnO nanoparticles. Besides that, gum arabic as eco- friendly stabilizer had shown good
performance on stabilized the nanoparticles within the range of investigated microwave irradiation time.
What is the purpose of arabic gum in this work? The importance of gum Arabic on the synthesis of ZnO should be explained to differentiate this work from common ZnO synthesis.
I had added the importance of gum arabic as stabilizing agent in line 57-60
Research gap is clearly not highlighted at the last paragraph. Mentioning the usage of Dynamic Light Scattering (DLS) is not considered as research gap of the work.
In Line 63- 69 I tried to explain my research gap.
Materials and methods:
Section 2.1 Line 1: Mention the brand for zinc nitrate hexahydrate Zn (NO3)2.6H2O and sodium hydroxide and from where the materials were purchased.
Line 79-80
Both zinc nitrate hexahydrate Zn
(NO3)2.6H2O , 98%, Aldrich and sodium hydroxide , 98.9%, Bendosen of analytical grade were used without further chemical treatment and purification.
Section 2.2 Line 3: Then the obtained solution was heated for 2 minutes in the microwave running at 350W. How do you consider irradiation time? Is this 2 minutes counted as irradiation time as well?
No, these 2 minutes is not considered as irradiation time. These 2 minutes is apply to dissolved the gum arabic and Zinc nitrate. The irradiation time is counted when the NaOH solution as reducing agent added and exposed to microwave heating.
How do you choose the irradiation time (2 minutes, 4 minutes, 6 minutes and 10 minutes)? They are very close in range.
Actually in my experiment, when I used longer irradiation time, my ZnO solution sample simply burn off. Therefore, I need to find a
close range to investigate it. Some researchers reported the irradiation time from 1 to 15 minutes.
UV-Vis analysis. Is the solution analysed contains a totally dissolved ZnO?
Yes, the solution analysed is stable resulted by gum arabic. Therefore the UV vis analysis can’t be done directly. I had experience using other stabilizer such as chitosan, ascorbic acid, gallic acid and starch but the ZnO solution is was not stable and precipitated make the UV vis can’t be read directly.
Results & discussion:
Remove Para 1 and Para 2 from this section. This kind of paragraphs should be located in Literature Study. Results and discussion should only focus on the finding of the work.
Yes, I have remove Para 1 and Para 2
Para 3 Line 7: ….might be cause of the protective role of gum arabic, as it retards the growth and agglomeration of nanoparticles by steric effect. Reference is needed for this statement
I have put the reference in Line 118
Para 3 Line 7: ….might be cause of the protective role of gum arabic, as it retards the growth and agglomeration of nanoparticles by steric effect. What happens to this effect at shorter time (2 minutes, 4 minutes)?
At shorter time, the gum arabic also retards the growth and agglomeration.
Para 3 Line 8: However, at 10 minutes of microwave irradiation time, the aggregates nanoparticles size increased to 225 nm. Why however? Isn’t the trend similar with 2 - 6 minutes?
Yes, the trend is similar. I had removed the
“however” and put 34% increase of nanoparticles size.
Para 3 Line 11: …. was mainly due to the fact that both processes of nucleation and crystal growth were greatly affected by microwave irradiation time which indirectly promoted the larger particles. This reason is given for 10 minutes of microwave irradiation time.
Previously, 6 minutes irradiation time has been associated with Arabic gum. How is this different?
In my opinion, at 2 minutes to 6 minutes of irradiation time, the size of nanoparticles not much increase because gum arabic play it role to control the growth by steric stabilization. Yet still the process of nucleation and crystal growth were affected by microwave irradiation time, resulted increasing size with the
microwave irradiation time.
At 10 minutes of irradiation time, longer microwave irradiation times will directly increase the heating rate that will effected the gum arabic coating to stabilized the
nanoparticle resulted increase in the aggregates
nanoparticles size almost 34%.
Figure 1 b) is not clear. Re-plot. The image was taken from the DLS image results. So I can’t replot it. But I had made the figure clearer than before. I am sorry for this.
Para 3 Line 17: …microwave assisted
synthesis resulted a unimodal narrow particle size distribution of ZnO nanoparticles. Why is this being highlighted? Explain the
important of having unimodal narrow particle size distribution.
A unimodal narrow particle size distribution will directly demonstrated monodisperse condition of the ZnO nanoparticles solution.
Monodisperse condition will indicated the stable colloid solution of ZnO nanoparticles.
Improve Figure 2 c). Refer literature.
Para 8 Line 4: Table 1 shows the calculated average size of ZnO nanoparticles synthesis in 2 minutes of irradiation time was 25 nm.
This result supported the FESEM image of primary ZnO nanoparticles. What you are calculating from XRD is average crystallite size, not particle size as shown in FESEM.
Use BET analysis instead
I have removed the sentence of
“This result supported the FESEM image of primary ZnO nanoparticles”.
I will do the BET analysis to improve my work.
But I am very sorry; I do not have enough time for sending sample for that analysis to be include in this paper.
Thank you for your suggestion.
Conclusion:
Line 3: Thanks to gum arabic that enable controlling the size as well as the
morphology.. Rewording is required. Also this statement is not proven in this work
I have removed this sentence and make a conclusion based on microwave irradiation time.
The writing of the manuscript needs
significant modification in terms of sentence structure (long sentences) and grammatical elements (e.g the usage of articles; a, the).
For example: Thanks to gum arabic that enable controlling the size as well as the morphology of the obtained spherical ZnO nanoparticles aggregates with the average sizes 168 nm to 180 nm within 6 minutes microwave irradiation time at 350 Watt microwave power. (Too long)
The use of microwave assisted synthesis.
This should be microwave-assisted synthesis. I had made sure the whole manuscript use microwave-assisted synthesis.
