Silver atomic properties

One way that a solid metal can accommodate another is by substitution. For example, sterling silver is a solid solution containing 92.5% silver and 7.5% copper. Copper and silver occupy the same column of the periodic table, so they share many properties, but copper atoms (radius of 128 pm) are smaller than silver atoms (radius of 144 pm). Consequently, copper atoms can readily replace silver atoms in the solid crystalline state, as shown schematically in Figure 12-4. 

This linear combination is clearly different from (3). The implication is that the two-dimensional vector space needed to describe the spin states of silver atoms must be a complex vector space an arbitrary vector in this space is written as a linear combination of the base vectors sf with, in general complex coefficients. This is the first example of the fundamental property of quantum-mechanical states to be represented only in an abstract complex vector space [55]. 

Abstract Silver clusters, composed of only a few silver atoms, have remarkable optical properties based on electronic transitions between quantized energy levels. They have large absorption coefficients and fluorescence quantum yields, in common with conventional fluorescent markers. But importantly, silver clusters have an attractive set of features, including subnanometer size, nontoxicity and photostability, which makes them competitive as fluorescent markers compared with organic dye molecules and semiconductor quantum dots. In this chapter, we review the synthesis and properties of fluorescent silver clusters, and their application as bio-labels and molecular sensors. Silver clusters may have a bright future as luminescent probes for labeling and sensing applications. 

It was also observed, in 1973, that the fast reduction of Cu ions by solvated electrons in liquid ammonia did not yield the metal and that, instead, molecular hydrogen was evolved [11]. These results were explained by assigning to the quasi-atomic state of the nascent metal, specific thermodynamical properties distinct from those of the bulk metal, which is stable under the same conditions. This concept implied that, as soon as formed, atoms and small clusters of a metal, even a noble metal, may exhibit much stronger reducing properties than the bulk metal, and may be spontaneously corroded by the solvent with simultaneous hydrogen evolution. It also implied that for a given metal the thermodynamics depended on the particle nuclearity (number of atoms reduced per particle), and it therefore provided a rationalized interpretation of other previous data [7,9,10]. Furthermore, experiments on the photoionization of silver atoms in solution demonstrated that their ionization potential was much lower than that of the bulk metal [12]. Moreover, it was shown that the redox potential of isolated silver atoms in water must... 

In summary, there is evidence that the multitalented sulfur sensitization product can trap electrons, can trap holes to reduce recombination, can stabilize photolytic silver atoms, and can accelerate reduction sensitization. Conceivably, each of these properties could be of importance for latent image formation under at least some conditions. The silver sulfide centers are not of uniform size, they probably are not uniformly related energetically to the silver halide matrix, and they may differ in chemical consititution. 

The latent image centers according to this concept could contain many hundreds of silver atoms, and "must possess metallic or quasi-metallic properties." Migration, even through the grain interior, of the silver formed by chemical sensitization is implicit in this account of latent image formation. 

The dyes must also have appropriate redox properties to function properly as sensitizers. If the dyes are oxidized too readily in the ground state, silver atoms can be prematurely and unselectively reduced, and this causes photographic fog. Fog is the unwanted, indiscriminate reduction of silver. Photographic fog causes a loss of signal-to-noise ratio and degrades image quality. The redox potentials of sensitizing dyes have also been extensively measured and correlated to performance [15],... 

The electronic properties of small silver clusters chemisorbed on AgBr have been calculated by Baetzold (66) using MO theory. This problem deals with catalysis since, as Hamilton and Urbach (67) have described, the silver centers are catalysts for the chemical reduction of AgBr grains. By using various experimental techniques, they indicate that a minimum size cluster of 4 Ag atoms is required for the catalysis. This suggests that some properties of 4 bonded silver atoms are different from atomic and perhaps like bulk properties, which could account for the catalysis. 

Vibronic coupling model used to explain the dynamic and energetic properties of the octahedral Ag°06 cage complex (A), appropriate for a silver atom in site 1 of faujasite-type zeolites (5). 

Rather dramatic alterations in the electronic properties and relaxation dynamics of supported silver atoms and clusters have been traced to extremely subtle differences in ground and excited state guest-host interaction potentials. For Ag° and Ag2+ in faujasite zeolites, pronounced changes in their optical... 

Here is a situation where the number of electrons lost is not equal to the number of electrons gained—processes that must occur simultaneously with an equal number of electrons. To remedy the situation, you must call upon the distributive property of mathematics. Multiply the silver half reaction by 2 to get an equal number of electrons lost and gained, and at the same time, correct the coefficients for the silver atom and ion in the equation. 

Coupling pulse radiolysis with time-resolved spectroscopy also allowed the determination of the transient absorption spectra of hydrated silver atom and of the first silver clusters showing that the absorption properties of silver atoms and metal aggregates in solution are different from that of bare clusters in gas phase. Silver atom presents an absorption maximum at 360 nm in water,while it absorbs at substantially shorter wavelengths in argon (292-310 nm) or in xenon (322-333 nm) atmosphere. ... 

Pulse radiolysis experiments also allowed the study of the reactivity and the redox properties of transient species such as silver atoms and silver clusters. Ag° reacts faster than Agj and both species act as strong electron donors since their respective redox potentials are... 

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