Optical Absorption and Photoluminescence Spectroscopy of the Growth of Silver Nanoparticles

Results obtained from the optical absorption and photoluminescence (PL) spectroscopy experiments have shown the formation of excitons in the silver-exchanged glass samples. These findings are reported here for the first time. Further, we investigate the dramatic changes in the photoemission properties of the silver-exchanged glass samples as a function of postannealing temperature. Observed changes are thought to be due to the structural rearrangements of silver and oxygen bonding during the heat treatments of the glass matrix. In fact, photoelectron spectroscopy does reveal these chemical transformations of silver-exchanged soda glass samples caused by the thermal effects of annealing in a high vacuum atmosphere. An important correlation between temperature-induced changes of the PL intensity and thermal growth of the silver nanoparticles has been established in this Letter through precise spectroscopic studies.

Figure 1

Deconvoluted XPS spectra of Ag $3d_{5/2}$ photoelectrons from silver in soda glass samples, (a) as-exchanged, postannealed at (b) 450 °C, (c) 600  °C, and (d) polished sample after annealing at 550 °C. Low and high energy peaks in the XPS spectra correspond to ${\mathrm{A}\mathrm{g}}_2\mathrm{O}$ and Ag, respectively (for details, see Table ).

Figure 2

(Top) (a) Formation of excitons in AgO is clearly seen in the optical absorption spectra for the silver-exchanged soda glass sample; (Below) Optical absorption spectra in the silver-exchanged soda glass samples due to postannealing at (b) 600 °C, (c) 500 °C, (d) 450 °C, and (e) 380 °C. Inset figure shows the increase of SPR absorption at 3 eV due to the thermal growth of silver nanoparticles in the soda glass sample.

Figure 3

(a) Room-temperature photoluminescence spectra from the silver-exchanged soda glass sample and from the postannealed samples at (b) 380 °C, (c) 450 °C, (d) 550 °C, (e) 600  °C, along with the glass substrate.

Figure 4

Experimental photoluminescence spectra (as seen in Fig. 3) are further shown here as a sum of two Gaussian spectral functions. In the figure, symbols are the data and dashed lines are the fitted functions to the data.