Silver plasmon

PLASMONIC SILVER FILMS APPLICATION TO ENHANCING OF STAINING DYES SECONDARY EMISSION... 

Enhancement and quenching of the secondary emission of poly-L-Iysine stained by eosin and hematoxylin immobilized between two plasmonic silver films (PSFs) are reported. Optical engineering of PSF involving the turning of localized plasmon (LP) band in resonance to dyes absorption and fluorescence bands is discussed as the way to successful PSF application in clinical assays. 

The plasmonic silver films put in pairs as an object-plate and a cover glass allow significantly (up to 3-4 times) increase the staining dyes fluorescence. This effect is observed in the case of optical tuning of LPs. The deposition of hematoxylin-eosine-poly-L-lysine moiety between two plasmonic silver films is carried out as a real biopsy material tincturing in histology. These results may be adopted for clinical assays with the use of biomedical fluorescent microseope. 

Plasmonic silver films application to enhancing of staining... 

The condition corresponds to the excitation of localized surface plasmons. Silver can satisfy this condition for visible light. 

Among metallic particles used in plasmonics, silver nanoparticles are widely studied due to the particular optical, spectroscopic and catalytic properties of silver [4-8]. They have been largely used in catalysis [9,10], biological labeling [11,12], photonics [13-15] and surface-enhanced spectroscopies [16,17]. Moreover a rich literature is now available for the synthesis of Ag nanoparticles [18, 19] (see also Chapter 10). 

N. Kalfagiannis, P.G. Karagiannidis, C. Pitsalidis, N. Hastas, NT. Panagiotopoulos, P. Patsalas, S. Logothetidis, Performance of hybrid buffer Poly(3.4-ethylenedioxythiophene) Poly (styrenesulphonate) layers doped with plasmonic silver nanoparticles, Thin Solid Films 560 (2014) 27-33. 

Y. Yang, X. Lin, J. Qing, Z. Zhong, J. Ou, C. Hu, X. Chen, X. Zhou, Y. Chen, Enhancement of short-circuit current density in polymer bulk heterojunction solar cells comprising plasmonic silver nanowires, Appl. Phys. Lett. 104 (2014) 123302 (1) -123302 (4). 

CuNPs) in Fig. 7 shows the monodisperse and uniformly distributed spherical particles of 10+5 nm diameter. The solution containing nanoparticles of silver was found to be transparent and stable for 6 months with no significant change in the surface plasmon and average particle size. However, in the absence of starch, the nanoparticles formed were observed to be immediately aggregated into black precipitate. The hydroxyl groups of the starch polymer act as passivation contacts for the stabilization of the metallic nanoparticles in the aqueous solution. The method can be extended for synthesis of various other metallic and bimetallic particles as well. 

FIG. 9 Silver nanoparticles capped by 4-carboxythiophenol electrostatically adsorbed to positively charged octadecylamine monolayers, (a) Mass uptake versus number of layers at subphase pH 12 and pH 9 the inset shows the contact angle of water versus the number of layers, (b) Absorbance spectra as a function of the number of layers transferred (left), with the inset showing the plasmon absorbance at 460 nm versus the number of layers. Thickness versus number of layers as determined by optical interferometry is shown on the right. (Reprinted with permission from Ref. 103. Copyright 1996 American Chemical Society.)... 

When the silver nanocrystals are organized in a 2D superlattice, the plasmon peak is shifted toward an energy lower than that obtained in solution (Fig. 6). The covered support is washed with hexane, and the nanoparticles are dispersed again in the solvent. The absorption spectrum of the latter solution is similar to that used to cover the support (free particles in hexane). This clearly indicates that the shift in the absorption spectrum of nanosized silver particles is due to their self-organization on the support. The bandwidth of the plasmon peak (1.3 eV) obtained after deposition is larger than that in solution (0.9 eV). This can be attributed to a change in the dielectric constant of the composite medium. Similar behavior is observed for various nanocrystal sizes (from 3 to 8 nm). 

Link, S. and El-Sayed, M. A. (1999) Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods. 

Simon, H. J., Mitchell, D. E. and Watson, J. G. (1974) Optical second-harmonic generation with surface plasmons in silver films. Phys. Rev. Lett., 33, 1531-1534. 

From these examples we may conclude that, as was indicated above, the question of having or not having a quantum confinement in a distinct particle allows different answers. All we may notice in this case is that gold, silver or copper particles of a distinct size must possess confined electron gases, but nanoparticles being too small to show a plasmon resonance cannot be excluded as having no confined electrons. On the contrary, as will be shown later by means of the Auss cluster. 

Remarkably the position of the final plasmon peak of the alloy particles is dependent on the molar ratio of gold to silver nanoparticles. When the ratio is shifted favoring either metal, an alloy of any desired composition can be formed. This alloying phenomenon indicates that it is possible for true tuneability of the properties of a set of nanoparticles. 

In this chapter, photoelectrochemical control of size and color of silver nanoparticles, i.e., multicolor photo-chromism [1], is described. Silver nanoparticles are deposited on UV-irradiated Ti02 by photocatal5dic means [2]. Size of the nanoparticles can be roughly controlled in the photocatalytic deposition process. However, it is rather important that this method provides nanoparticles with broadly distributed sizes. The deposited silver nanoparticles are able to be dissolved partially and reduced in size by plasmon-induced photoelectrochemical oxidation in the presence of an appropriate electron acceptor such as oxygen. If a monochromatic visible light is used, only the particles that are resonant with the light are dissolved. That is, size-selective dissolution is possible [3]. This is the principle of the multicolor photochromism. 

Awazu, K., Fujimaki, M., Rockstuhl, C., Tominaga, J., Murakami, H., Ohki, Y., Yoshida, N., and Watanabe, T. (2008) A plasmonic photocatalyst consisting of silver nanoparticles embedded in titanium dioxide. Journal of the American Chemical Society, 130 (5), 1676-1680. 

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