Extinction Effect of Gold Nanocatalysts on Photocatalytic Activities under Plasmonic Excitation
Round 1
Reviewer 1 Report
The work of D. Kim and Y. Kim present interesting and innovative results on the influence of the size of Au NPs on reaction rate of the reduction of ferricyanide to ferrocyanide.
The synthesis and characterization of NPs, although conventional, is well performed.
However, I have some problem with the reaction test:
- Reaction tests are performed at iso-absorbance, i.e. Abs=1 at 532 nm for all NPs solutions. No information is given on the concentration of NPs which could have an impact on the catalytic activity.
- Reaction tests are performed at very high absorbance, i.e. Abs=1 at 532 nm, which means that 90% of the light intensity is absorbed in 1 cm and a huge difference in light intensity within the path of the quartz cuvette is estimated. The authors should study the reaction at low absorbance (i.e. below 0.3) and consequently longer reaction time. The results will thus be more convincing.
- Kinetics determination at 240 nm with the absorbance above 1.5 is irrealistic with a classical UV spectrophotometer.
Figure 3: the y axis could be change to concentration instead of “change in molarity”.
Figure S2: an enlargement of the 400-450 nm zone, in addition to the full spectra, is necessary.
In conclusion, the objective is interesting but the reaction test must be improved before resubmission.
Author Response
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Reviewer 2 Report
This manuscript investigated the Au size on plasmonic catalysis. The increasing scattering is found to decrease the reaction rate due to the competitive decrease of absorption. The results are interesting and straightforward based on the previous publication. The manuscript should be improved by elucidating the following issues:
- Compared to ref. 14, the current data of Fe+3 reduction is nearly undetectable ( Fig. S2). The local magnified figure should be improved.
- Relative to electron transfer, the hole scavenger is critical for the reaction. Has the concentration of 11-metaptoundecanoic acid been investigated? Has the concentration been optimized?
- The “i” is missed in ε1+ε2 in page 7.
- How to determine the extinction rate of Fe3+ at 419 nm and Fe2+ at 240 nm should be presented. The reference should be given.
- The definition of quantum efficiency should be explained and relative ref should be given.
- From Fig. 4, the catalytic reaction rate is still pretty small. Since the scattering and absorption cross-section dependent the shape, size and materials (ref. such as, Introduction to Laser Micro-to-Nano Manufacturing, springer book 978-3-030-59313-1), what is the practical solution to improve the reaction rate?
Author Response
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Reviewer 3 Report
The manuscript presented by Donghee Kim and Youngsoo Kim about Extinction effect of gold nanocatalysts on photocatalytic activities under plasmonic excitation, the manuscript looks interesting, Au NPs with different diameters were successfully prepared by Turkevich method and seeded-growth method, the authors found that the absorption cross-section of the Au NPs gradually increased as the size of the Au NPs increased. However, some sentences were written not so well, the English should be improved, and there are some small mistakes could be found in the content and references, the mistakes should be corrected.
Author Response
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Round 2
Reviewer 1 Report
1/ Why do authors use the same molar absorption coefficient for the different sizes of Au NPs? Where does this value come from?
2/ Lines 153-154 one can read: … Figure 3 shows a plot of the change in molarity as a function of irradiation time with four different sizes of Au NPs. The molarity in the y-axis was calculated from the change in absorbance using the Beer-Lambert law.
This could be changed in:
Figure 3 shows the increase in Fe2+ concentration as a function of irradiation time and as the size Au NPs. The Fe2+ concentration was determined using the Beer-Lambert law at 420 nm and using the molar absorption coefficient of YYY (Ref).
Same in the caption and the y axis of figure 3.
3/ My remarks on the first version are still valid:
- The assumption on the identical concentration of the particles in the four experiments must be specified
- The error associated with measuring a concentration with absorbance greater than 1 is large and must be mentioned in the text regardless of the calculations, subtractions of spectra made after the measurement. This also must be highlighted in the text as well as the justification of the concentration.
4/ A decrease of the absorption at 525 nm could be also noticed, of the same order as the decrease of the absorption at 420 nm. Could the authors comment on that particular point?
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Reviewer 2 Report
The authors' response should be integrated into the final manuscript rather than simply answering the reviewer's report.
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