From UV−vis absorption studies it is clear that wavelength
of the SP band depends on particle size. It is evidenced by an
increase in the wavelength (λmax) of SP band from 395 to 417
nm for nanoparticles of different size. Colloidal solutions of the
complexes are stable for over one month as evidenced by UV−
vis spectroscopy. Red shift is also accompanied by slight
broadening of the SP band toward long wavelength region.
From UV−vis spectral studies we conclude that size of the
nanopartilces can be controlled by varying the ratio of capping
agents. Also, it was shown that it involves strong interaction
between 1/2 and surface of the nanoparticles. Further, Ag/[1/
2] ratio indicated that only a small amount of 1/2 is sufficient
for effective coating of the AgNPs surface and provide stability
in solution.