Hello everyone

I work with the synthesis of AuNPs using the method of HAuCl4 reduction with sodium citrate; I already have pre-established the synthesis and have done it several times with good reproducibility obtaining nanoparticles with an average size of 18 nm. Recently, I started using a new bottle of HAuCl4 reagent since I ran out . This bottle has the same specifications(Same brand, purity) and now I’m obtaining nanoparticles of bigger size. I don’t know what’s happening because I’m doing everything as before, the only change is the production batch of the HAuCl4 reagent. When reviewing the certificates of analysis for each batch of the reagents I noticed that the new precursor I’m using has more trace elements (metals) that the one before, being Ca the one that has the biggest difference.

So the question I have is that if someone knows what’s causing this difference in the size of the obtained nanoparticles? And if it might be possible that the trace elements are causing this.