Dear All

I have been trying to make Cu nanoparticles for a long time, but I am unable to do it. I always obtain big Cu particles with a size about 200~ 300 nm all the time. I have read most of

available papers about making Cu NPs and tried to reproduce what they did. Yet, none of my experiment is successful. One of the synthesis recipes I am trying is described as follows:

Precursor Solvent Capping Agent Temperature Reducing Agent

76 mg CuCl2*2H2O 100 ml H2O 8.8 g PVP 45 degrees C 3.522g ascorbic acid

76 mg CuCl2*2H2O 100 ml H2O 4.4 g PVP 45 degrees C 3.522g ascorbic acid

116 mg Cu(NO3)2*2.5H2O 100ml H2O 8.8 g PVP 45 degrees C 3.522g ascorbic acid

116 mg Cu(NO3)2*2.5H2O 100ml H2O 0 g PVP 45 degrees C 3.522g ascorbic acid

PVP (MW= 55000) from Sigma-Aldrich

What I did is prepare two separate solutions: Sol 1 : Cu2+ precursor and half amount of total PVP in 50 ml; Sol 2 : Ascorbic acid and half amount of total PVP in 50 ml. Then, I mix them in a 250 ml of rounded-bottom flask with stirring. Next, heat up the mixture at 45 degrees C (in a water bath). According to this paper:

One-step green route to narrowly dispersed copper nanocrystals, Journal of Nanoparticle Research (2006) 8:965–969 Springer 2006 DOI 10.1007/s11051-005-9065-2,

the reaction should take 3 hrs to finish. However, the reaction only takes couple of minutes when I heat the mixture at 45 degrees C. Then, I get big copper particles (200~300 nm)

What I feel is it seems like the PVP does not have any effect on the particle size at all. It does not have a big difference in the particle size whether PVP is added or not. I also found out that the reduction reaction will occur and give us big Cu NPs or it will not occur at all whenever I tried to make Cu NPs. I just cannot control the size to be 10~20 nm. PVP does not work at all. Does anyone have similar experience? Any hint or suggestion is deeply appreciated! Is there any reliable method to make Cu NPs?

Thank you!