UV-visible reflectance spectra of nanocrystalline silver compacted under different pressures

Nanocrystalline silver samples compacted under different pressures have been studied by X-ray diffraction and ultraviolet-visible reflectance spectroscopy. It is shown that the reflectance spectra exhibit an intense band at 315 nm, three weak bands at about 240, 380 and 490 nm, and a long tail at the long-wavelength side. Their origins are given. With increasing the compacting pressure, an opposite peak-shift effect of the surface plasmon resonance (SPR) was observed. It is concluded that the collaborating effects of particle aggregate and the unit-cell contraction both induced by the compacting pressure can explain these variations.