I have synthesized gold nanoparticles that show UV Vis peak at 522nm and were bright pink immediately after synthesis. Over a span of 24hrs, the Solution shows visible colour change from pink to dark purple despite being stored in the dark at 25 degree celcius. What might be the problem?
This is due to the fact that nanoparticles are growing which is natural. The nanoparticles will try to reduce the surface area by that. Eventually they will aggregate and will settle down under the influence of gravity. You can check through the UV-Vis spectroscopy the shift of the plasmonic peak. You can try polymeric ligands to slow down the process if that's possible
Partha Pratim Chowdhury
Very often they write the phrase you wrote “The nanoparticles will try to reduce the surface area by that”. If there was a nanoparticle, and then it combined with others, then the area increases. During aggregation, the specific area of nanoparticles with a dimension of m2/g decreases. .
Hi! Store the solution with gold nanoparticles at a temperature of +4 C
The most important principle of keeping citrated gold nanoparticles is to prevent contamination with ions that can cause their aggregation. For this reason, you must use completely clean equipment washed with aqua regia and deionized water.
To store the solution of gold nanoparticles, put it in the refrigerator and in dark place.
The storage container should be glass and do not use metals.
If you store in plastic containers, they have already been treated with 12M NaOH.
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