I've attempted to use this method to synthesize copper nanoparticles. Copper nanoparticles can be synthesised using a variety of precursor materials. CuSO4, distilled water, NaOH, and EDTA are consumed. In order to prevent the formation of copper oxide species, EDTA was used as an oxidation control agent. Because of their smaller size and greater surface area, metal nanoparticles are typically more oxidatively sensitive. The solution was mixed with NaOH to keep the pH between 10 and 11.As we have followed the recipe as stated but the addition of EDTA was not specified in the procedure.Thus, I added the EDTA right after adding the other reagents; this addition simply stops the reaction, and even after a 24-hour reaction time, no product or particles were formed.Could someone please clarify when EDTA should be added to the finished mixture and provide any additional information about why the reaction failed?
Dear Muhammad Saad Atique, I think you added too much EDTA. It has two essential roles: chelation of the metal which protect it against oxidation, and preventing NPs against growth by agglomeration. Its reducing activity is also another benefit. Possible explanation of the failed reaction is that too much EDTA lead to the shift of the pH to highly acidic medium, since the chelation reaction lead to the exchange of the protons (H+) of the EDTA acid groups with Cu, and formation of H2SO4 strong acid. You can check the pH to exclude this fact. Please have a look at the following paper. My Regards
https://doi.org/10.1016/j.matlet.2011.06.037
Dear Muhammad Saad Atique , I think you have a conceptual error about the effect of EDTA. Because EDTA forms a strong complex with Cu(2+), it actually makes oxidation of copper easier (moves the equilibrium redox potential to a more negative value). I don't have first-hand knowledge of the procedure, but my guess is that a small (SMALL) amount of EDTA can be added beneficially after the nanoparticles have been formed, i order to remove the oxide film on their surface.
Working under nitrogen may also make the procedure more forgiving.
Also: What is the reducing agent? CuSO4 will not spontaneously get reduced to Cu(0). Maybe you forgot to mention it? EDTA is not an effective reducing agent. NaOH isn't either.
Muhammad Saad Atique I believe in the presence of water, air or any other oxygen carrying entity that it is impossible to produce copper nanoparticles without an oxide film on the outer layer (in the top 10 - 15 atomic layers the copper will be in the +2-oxidation state). ESCA/XPS should show this and the technique is essential for surface studies of nanomaterials. The reason for this is that oxygen will pull species to the surface by a phenomenon called chemisorption induced segregation. The only way to avoid this is preparation in inert atmospheres excluding air, water or other oxygen containing entities and keeping the prepared material in vacuo or in a similar inert atmosphere. If oxide is a 'showstopper' it could be removed in any subsequent step (e.g. for a reaction), for example, by using a metal cleaner such as Brasso or better still utilizing a reducing atmosphere of hydrogen. For further general information please view this webinar (free registration required). Good luck with your research.
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
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