Silver plasmons

Longer irradiation than that shown in Fig. 81 resulted in decreased absorption of AgT at 275 nm and in an increase at 380 nm, which are characteristic of a developing silver plasmon band [525, 526]. 

The reaction described by Eq. (25) occurs in the millisecond time scale and results in an exponential increase in the conductivity of the solution and a parallel decrease of the absorbance at 440 nm. The net result of the reaction was both a blue shift and a narrowing of the silver plasmon absorption band (see 0 -> a change in Fig. 83) [506]. 

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... 

Mixing equal concentrations of two separately prepared solutions of colloidal lead and silver particles (each degassed by repeated freeze-pump-thaw cycles on a high-vacuum line and mixed under vacuum) resulted in a slow blue shift of the silver plasmon band from 390 nm to 337 nm and a concomitant broadening... 

Tiemblo P, Benito E, Garcia N, Esteban-Cubillo A, Pina-Zapardiel R, Pecharroman C (2012) Multiscale gold and silver plasmonic plastics by melt compounding. RSC Adv 2 915-919... 

Rebekah A. Drezek 25.5 Silver Plasmon Resonant Particles for Bioassay ... 

The enhancement of Eu(III) luminescence in glasses can be also achieved by embedding small silver particles (Malta et al., 1985) in the glass. The question whether the enhancement is due to interaction of the silver plasmons with the medium, or due to radiative trapping of Eu(III) luminescence is still disputable. 

The efficiency of the system can be increased additionally by silver plasmons as will be explained later. 

Such phenomenon of increase of fluorescence in the presence of silver plasmons has been reported earlier however, the separation of absorption from emission prevents self-absorption when the fluorescent light travels along the way. It should be stated that the lifetimes of the fluorescent molecules in the presence of silver nanopartides decreased as a result of the increase in transition probabilities. In the case of DH-BP(OH)2 in polyvinyl butyral (PVB), lifetime of the DH-BP(0H)2 fluorescence in the PVB films appeared nearly the same in the absence and presence of silver nanopartides -rf= 3.55 0.02 ns and -rf=3.75 0.01 ns, respectively. This important observation indicates that the increased fluorescence efficiency does not result from increasing emission rate kf, but rather from increasing efficiency of excitation in the neighborhood of the Ag NPs. The interaction of the fluorophore molecule with the scattered light from silver surface plasmons in the neighborhood of the Ag NPs enhances the excitation of the fluorophore. This can be understood since absorption and... 

The interaction of RE with silver NPs was also used for increasing upconver-sion of infrared energy, which cannot be used for solar cells, to visible light where the solar cells are sensitive. Some examples can be foimd in Refs. [65,66] and in the recent paper by Sun et al. [67], where upconversion provides an additional example in this direction. Energy transfer enhanced by silver plasmons allowed a strong upconversion from infrared light absorbed by Yb to visible photoluminescence of Er. 

Reisfeld, R., Saraidarov, T., Panzer, G., Levchenko, V., and Gaft, M. (2011) New optical material europium EDTA complex in polyvinyl pyrrolidone films with fluorescence enhanced by silver plasmons. Opt Mater., 34, 351-355. 

Verticillium has also been shown to synthesize silver nanoparticles [91]. From a TEM analysis, it was determined that the Ag(0) nanoparticles synthesized via the reaction of Verticillium with silver ions were polydispersed, with a mean size of 25 12 nm. Silver nanoparticles synthesized through the incubation of aqueous Ag(I) ions with A.Jlavus [92] were monodispersed, with an average size of approximately 9nm 1.6 nm as determined by TEM. An XRD analysis of these samples confirmed the silver as fee silver, based on the 111, 200 and 220 diffraction peaks. Again, SEM showed the silver nanopartides to be located on the outside of the fungal mycelium. The UV-visible data showed an initial increase in silver plasmon resonance with time, but this then remained constant after 72 h. Fusarium oxysporum has also been shown to synthesize Ag(0) nanopartides extracellularly [87] here, a TEM analysis showed the nanopartides to be polydispersed, ranging in size from 5 to 50nm. The SAED analysis showed diffraction of the silver 311, 200... 

A. Nature of the Silver Plasmon Band in the Presence of a Surfactant... 

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