I prepared GNPs by 0.5mM of HAuCL4 and 0.39 mM of Na-cit. the Absorbance is good but DLS measurements give high PDI = 0.431.,pH is 6.51, and sample was stored at 4 oC
Any ideas to reduce the PDI? Thanks
Using ultrasounds or microwave-assisted conditions might help to get a more homogeneous medium, so that the resulting nanoparticles would be more monodisperse.
You could try to look at the effect of pH on your preparation.
Article Slight pH Fluctuations in the Gold Nanoparticle Synthesis Pr...
The larger PDI may be either oligomerisation/aggregation or could also be a shape effect.
Finally, keep in mind that light scattering is intensity based, so this may make the polydispersity appear "worse" than for a number based technique like TEM.
https://www.materials-talks.com/blog/2017/01/23/intensity-volume-number-which-size-is-correct/
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