Metallic silver particles

Inhalation route. Anesthetized dogs exposed to metallic silver particles about 0.5 pm in diameter total dose deposited of 25 pg... 

Charge alteration on the surfaces of nanosized metallic silver particles has been investigated by simultaneously monitoring absorption and conductivity changes during pulse-radiolytic experiments [506]. Pulse radiolysis of a nitrous-oxide-(N20) saturated aqueous solution of 3.0 nm diameter metallic silver particles containing 0.2 M 2-propanol resulted in electron injection to the colloid. NzO functions to double the yield of hydroxyl radicals ( OH) generated in water... 

Hole injection into the silver particles was accomplished by allowing OH (formed in the pulse radiolysis of N20-saturated, aqueous, 3.0-nm-diameter Ag particle solution (Eqs. 22,23) in the absence of the -OH scavenger, 2-propanol) to extract electrons from the surface of colloidal, metallic silver particles. The process resulted in a red shift, broadening, and a decrease in intensity of the silver plasmon absorption band (see 0 - b change in Fig. 83) [506]. Addition of silver ions to metallic silver colloids elicited a similar change in the absorption spectrum [506]. 

Alteration of the silver plasmon band spectrum upon electron and hole injection has been rationalized in terms of changes in the density, Ne, and conductivity, o, of the electron gas in the metal particles as described by Eqs. (16)—(18) [506]. Thus, a decrease in Ne by electron extraction from the metallic silver particles increases Xc (Eq. 16) and thereby shifting the absorption maximum (Eq. 15) of the plasmon band to a longer wavelength (Fig. 83). A decrease in Ne also decreases a (Eq. 18), which leads, in turn, to an increase of w (Eq. 17) that is, to an increase in the bandwidth of the plasmon band absorption (Fig. 83). Similarly, the increase in Ne by electron transfer to the silver colloids is paralleled by a decrease in Xc (Eq. 16) and, hence, by a decrease in Xm (Eq. 15), as seen by the shift of the plasmon absorption band to a shorter wavelength (Fig. 83). Electron donation to the silver particles also causes an increase in cr (Eq. 18)... 

Electron transfer was mediated by metallic silver colloids whose surfaces contained either a strong (SH ) or a weak (CN ) nucleophile [531]. The former case is illustrated by changes in the absorption spectrum of a 1.0 x 10 4 M, deaerated solution of metallic silver particles, subsequent to the consecutive addition of 2.0 x 10 4 M NaSH and 3.0 x 10-4 M anthracene quinone sulfonic acid, AQS (Fig. 85) [506]. The origin of the intensity decrease and the broadening of the silver plasmon absorption band upon the addition of nucleophilic SH is incompletely understood. However, that an absorption... 

A study in dogs indicates that absorption of inhaled metallic silver particles with a median aerodynamic diameter of approximately 0.5 pm is extensive, and is not dependent upon particle size (Phalen and Morrow 1973). Absorption was measured in one dog that remained anesthetized during the entire period between exposure and sacrifice. In this dog, 3.1% (0.8 pg) of the deposited material was dissolved, transported out of the lungs, and was found mostly in liver and blood 6 hours after exposure a 1 pg/cm /day absorption rate for metallic silver was estimated by the authors. Up to 90% of the deposited silver was estimated to be absorbed into the systemic circulation based on all experimental data. Clearance from the lung to the blood was triphasic, with half-lives of 1.7, 8.4, and 40 days. 

Poly(oxyethylene)nonylphenyl ether (Igepal-20) has been used in a combined synthesis of nanometer grains of silver on fine-grain silica (Li et al, 1999b). This method uses Igepal in a hexane solution with silver nitrate dissolved in the aqueous phase. Hydrazine hydrate is then added to reduce the Ag after the fine droplets of micelle have been formed, resulting in metallic silver particles contained inside the micelle. Then tetraethylorthosilicate... 

Controlled growth of previously deposited very small silver particles can also be performed. The procedure involves to establish first the minimum temperature at which reduction of the metal proceeds in the bulk of the solution. With the reduction of silver ammine complexes by formaldehyde, the temperature to effect reduction in the bulk of the liquid is about 310K. It has been found that metallic silver particles catalyze the reduction of the silver ammine complexes. By suspension of a silica support covered with small silver particles in a solution of Ag(NH3)7 cooling the suspension to 273 K and subsequently injection of formaldehyde, controlled growth of the silver particles can be achieved. It is interesting that the silver particles... 

Malicka, J., et al. (2003) Fluorescence spectral properties of cyanine dye labelled DNA near metallic silver particles. Biopolymers 72 96-104. 

C) results in high frequency xenon chemical shift from NaX.This 5 = f (N ) variation has the classical form for zeolite -supported metals 8 which is high at low N ( strong metal - Xenon interaction ), decreases as N increases, due to rapid site exchange, then a new increase in 5 when the Xe - Xe interactions become sufficiently important. The very low xenon adsorption of this sample shows that the zeolite lost most of its crystallinity. However, it is known [ 11 ] that the decationized type X,lose their crystallinty after reduction at 300°C. The chemical shift observed in this case is due to the adsorption of xenon on the metal silver particles in a defect structure. 

In another study, where silver atoms were obtained by the reduction of silver ions originating from silver perchlorate (AgC104), particles were deposited on the surface of a colloidal (3-amino-propyl) trimethoxysilane (APS) functionalized nanosilica (Figure 20.7). The authors reported that the presence of metallic silver particle induced effective further depositiou of silver particles on the same silica particle (Zidki et al. 2007). 

To obtain the Ag/Si02 catalyst, we used the sol-gel method. We synthesized silica alkogels via alkaline hydrolysis and condensation of tetramethylsilane [Si(OCH3)4] in water-alcohol solution in the presence of silver amine complexes. Then we removed methanol at 290 and 120 atm and thus obtained Si02 aerogels containing the metal silver particles. 

Lakowicz JR, Ku a J, Shen Y et al (2003) Effects of metallic silver particles on resonance energy transfer between fluorophores bound to DNA. J Fluoiesc 13 69—77... 

Among the photochromic inorganic compounds [88-90], it is well known that silver halide particles in borosilicate or aluminoborosihcate glass exhibit reversible photochromism upon exposure to sunlight [91-93]. Upon irradiation, the silver ions are reduced to metallic silver particles, which are responsible for the... 

Figure 40.7 Formation of the metallic silver particles upon irradiation and sol-gel photochromic coatings based on AgCI. Particle size ranging from 8nm (yellow) to 30 nm (purple).

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