Discussion
Sharp absorbance in case of silver and gold nanoparticles observed in UV-vis spectroscopy is attributed to :
Answer: B
The sharp absorbance is due to oscillation of free electrons on the metal surface, the surface plasmon resonance.
In silver and gold nanoparticles, light drives the conduction electrons into a collective oscillation at the particle surface. At the resonance frequency this localised surface plasmon gives a strong, sharp band, near 400 nm for silver (yellow sols) and near 520 nm for gold (red sols). The band position shifts with particle size and shape.
Lattice phonons absorb in the infrared, size quantisation dominates in semiconductor quantum dots and very small clusters, and interaction among particles (aggregation) broadens and shifts the band rather than causing it.
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