Usually, unprotected AgNPs exhibit an absorption band with
a maximum at ca. 390 nm. UV−vis spectra of the synthesized
AgNPs with varying Ag/[1/2] ratio (03, 06, 10, 20) are shown
in Figure 7. Clearly, both 1/2 exhibit characteristic surface
plasmon (SP) resonances for spherical AgNPs [created by
addition of Ag/[1/2] (ratio; 03; average particle size ≈ 10 ± 2
nm)] at ∼395 nm, which was also followed by TEM
measurements. Shift in the position of SP band (390 nm,
unprotected AgNPs) by capping silver particles may be
attributed to bond formation between Ag clusters and free
pyridyl nitrogen from 1/2. The UV−vis spectrum also
exhibited typical bands due to π−π* transitions corresponding
to conjugated dipyrrinato ligands, which strongly supported
presence of the dipyrrin core.