On the Importance of Fresh Stock Solutions for Surfactant-Free Colloidal Syntheses of Gold Nanoparticles in Alkaline Alcohol and Water Mixtures
Gerardo Rosas
Round 1
Reviewer 1 Report
The author describes the synthesis of gold nanoparticles with alcohols and bases. From a technical point of view the study is sound. The presentation in the manuscript is clear so it can be published.
A comment to the concept: the author claims, also in the related publication this manuscript refers to (Chem. Mater. 2023, In 11
press, DOI: 10.1021/acs.chemmater.3c00090), that this synthesis route for metal nanoparticles is preferable over existing ones, because it is claimed to be more "green", simple and provides surfactant-free nanoparticles. However, this is not really convincing. E.g. the Turkevich synthesis works well and is reproducible and uses basically just water and sodium citrate and the metal precursor. Sodium citrate is not dangerous or hazardous in any way (in fact less hazardous than ethanol or methanol or NaOH), cheap and available. So the Turkevich synthesis might be claimed to be less "green" because it is not done at room temperature but apart from that it is probably even "greener" (less chemicals except water and mandatory precursor used). The citrate molecules are very easy to replace, so the surface is not at all blocked for catalytic activity, which has been shown in numerous experiments (including the authors' own ones). If the particles are immobilized on a surface for catalysis, it is not hard to remove any ligands (thermally or with UV/plasma). If they are in solution, their stability is often the bigger concern. The accessible surface is not useful, if in the catalytic process (often under comparably harsh conditions) the particles aggregate.
The author discusses the issues of reproducibility and how reporting could be improved. while such considerations should be elemental to good laboratory and reporting praxis, he is right in pointing it out, because in literature many syntheses lack reproducibilty. Regarding this, once more, the Turkevich protocol seems superior to the protocol presented by him, because it is quite reproducible and reliable in producing particles with a better quality than the ones presented here. So this is probably the reason why the protocol has not been broadly adapted until now. Having noted these critical remarks, it has to be emphasized that it is of course interesting and worthwhile to explore and study new synthesis routes. This is done here in detail and with a solid discussion overall, so the manuscript will be of interest for the community.
Finally it came to my attention that Figure 2a is the same as in the mentioned publication (Figure S1a), this should be properly attributed.
Author Response
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Reviewer 2 Report
In the literature, many investigations are related to the synthesis of gold nanoparticles, including the polyol method that uses different alcohols. The article must mention some of these investigations in the introduction section. In this method, alcohols are used as reducing agents and stabilizers at the same time.
On the other hand, the absence of a stabilizer can cause coalescence between the particles. In this work, it can be seen that figures 2 b and 2 e show the coalescence of the particles, while figures 2 a and 2 d show individual particles. In this case, the author must explain why these particles are stable.
The discussion in figure 2 is absent in the text.
NaOH is toxic.
In the same context, phrases should be avoided like this "it is a first surprising that it has not been considered and explored in more details before."
The abstract must be rewritten since it does not reflect the main objective of the work and the general results obtained. In the same way, the conclusions do not reflect the main findings derived from the investigation.
The manuscript is short compared with the results presented in the supplementary data. Therefore, the article should add and discuss some of the results from the supplementary data.
Some typographical and English language errors need to be corrected before publication.
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Reviewer 3 Report
The Manuscript (inorganics-2257228) entitled “On the importance of fresh stock solutions for surfactant-free colloidal syntheses of gold nanoparticles in alkaline alcohol and water mixtures” by Jonathan Quinson deals with the synthesis of gold nanoparticles in basic media.
This manuscript represents an extension of the work recently published on Chem. Mater. (DOI: 10.1021/acs.chemmater.3c00090 ) and compares the results obtained by using freshly prepared base solution (in PP vials) vs. aged stock solutions (in glass vials) both in ethanol and methanol. Likewise, the Chem. Mater. paper, I truly enjoyed reading this manuscript and I completely agree with the author when he states that far too often the synthesis reported in literature are very difficult, if not impossible, to be repeated in the lab.. I therefore recommend publication in Inorganics.
Author Response
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Round 2
Reviewer 2 Report
Some requested corrections to the manuscript were made. However, changing the next sentence in the abstract is still recommended as the results obtained by TEM are not extraordinary compared to others.
"it is a first surprising that it has not been considered and explored in more details before."
Is it worth emphasizing that synthesis has never been carried out this way? Almost every synthesis methods release has something new, so each one is a surprise.
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