Silver clusters nuclei

Fig. 10 (a) Fluorescence image of methanol-fixed NIH3T3 cells loaded with peptide encapsulated silver clusters for 1 h at room temperature, (b) Time profile of the time series images of cell stained with silver nitrate showing the fast silver cluster emission centered in the nucleus at short times with a maximum at 320 nm. Note that black indicates an intermediate intensity level in this color scheme [57]... 

As seal from Eq. (7.251), the value of TV depends upon several parameters of the system, e.g., the edge surface energy, . It also depends on the overpotential T, and one can see that the size of the critical cluster decreases with an increase in hjl. For 2D nucleation on quasi-perfect silver single crystals, the number of atoms in the minimum nucleus size at which AG begins to decrease with an increase in A varies from 25 to 67 atoms as t varies from -10 to -6 mV. 

If the concentration of is high, the reactions depicted by Eqs. (29)-(31) are faster than the coalescence reactions (Eqs. 10 and 11) with a fixed total concentration of atoms and the clusters now grow mostly by successive additions of supplementary reduced atoms (electron plus ion). It has been shown that once formed, a critical cluster, of silver for example,indeed behaves as a growth nucleus. Alternate reactions of electron transfer (Eqs. 32 and 34) and adsorption of surrounding metal ions (Eq. 33) make its redox potential more and more favorable to the transfer (Fig. 8), and autocatalytic growth is observed.The observation of an effective transfer therefore implies that the potential of the critical cluster is at least slightly more positive than that of the electron-donor system, i.e. °(M +/M ) > °(S/S-). 

There is evidence that the extreme enhancement of the Raman signal on a silver deposit comes from colloidal silver particles. Considering the special situation of a silver nucleus with adsorbed CN" ions, other explanations of the Raman results are possible, e.g., an adsorption of CN" on clusters of different sizes and charges. ... 

---