I am doing synthesis of nanoparticles of Ag and I am still using distilled water to prepare a solution of AgNO3. But because the distilled water ran out I used deionized. For almost 2 days after, I observed a very tiny coloration (purple) of my solution (it was completely transparent with distilled water)
I don't know if it's be possible? (the change of color)
or did something else happen?
I think you should repeat the experiment with DI water to confirm the phenomenon! but.... Deionizing water only takes away ions. However, distillation will take away other things (impurities). Deionized water has probably passed through several filters that have a slight electrical charge in the filter particles. This "charge" attracts ions (charged particles dissolved in the water), but not necessary all impurities.
I agree with Hadi. The change in the colour is possible due to the formation of AgNPs with different size than the ones you prepared in distilled water, and it is very normal by changing the media. You should repeat both experiments to confirm that and, if it is possible, analyse the results by TEM.
Deionized water is made by ion exchange, thus it may contain mostly organic impurities form the ion exchange resin. Distillation results in less organic contaminant.
Distilled water is usually passed through the ion exchange columns to get de-ionized water. You may check the difference in the pH of both distilled water and de-ionized water and note that pH has a significant effect on the size, shape and stability of electrostatically stabilized particles as is in your's case. I think that particles in your later preparation are less stable and have gone a kind of aggregation. Red color of silver nanoparticles is due to the linear aggregation of less stable silver nanoparticles to form chain-like structures. It is also possible that you hay have particles of several different sizes and shapes ......
In terms of the water, distilled water is most often considered Type II water with a maximum resistivity between 10-14 mOhm/cm^2 The impurities in distilled water salts can be both ions and organic residues. Deionized water can be either Type II (reverse osmosis) 10-14mOhm or Type I (RO + ion removal) >18.2 mOhm with less than 15 ppb total organic content. Most deionized water is Type I and is used in biology or electrochemistry where ultra high purity is needed. We use Type I for electrocatalysis measurements where even Type I water can effect your measurements if it is contaminated. You can consult the Millipore website which has great resources on water purification: http://www.millipore.com/lab_water/clw/capability
In terms of your silver solution, it might be because the silver ion is slightly less stable in a the deionized water leading to the formation of some gold particles. When we prepare Au and Ag particles we use distilled water without any issues.
I am working with deionized water and AgNO3 and can`t see any changes of colour.
1. check your water source - meaby some filters are old and dirty
2. check if you store your solution in some dark place - silver is sensible for light
Repetition of the experiment is needed to confirm the change in color. Since pH has the significant effect in preparing nano-particle, this should be checked.
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