Dynamic Light Scattering and UV-Vis Spectrophotometric Assessment of Stability of Metal Nanoparticles in Aqueous Medium

Stability of gold nanoparticles (AuNPs) has been studied in aqueous and ionic liquid
mediums. In each medium four different volumes of oil palm leaf extract has been used
as a stabilizer. The effect of the extract volume on the stability of AuNPs in the eight
samples has been studied using Dynamic Light Scattering (DLS), UV-Vis
spectrophotometry, and Zeta Potential testing methods. The results of the three tests
were taken for 5 weeks on a weekly basis and the change of the UV-vis absorbance,
surface potential and size results has been used to indicate the stability of the AuNPs in
the samples. Moreover the results of particles size as well as the surface potential
obtained from the DLS and zeta potential methods were used in calculating the stability
ratio based on the DLVO theory. Based on these calculations the change of stability ratio
with time was used as a quantitative definition of the nanoparticles stability in the two
testing mediums. The obtained results from both the stability ratio and UV-Vis
absorbance have shown that addition of the ionic liquid has significantly increased the
stability of the gold nanoparticles, however the quantitative results gave more specific.