Silver, colloidal

Plenary 3. Ronald E Hester et al, e-mail address reh York.ac.uk (SERS). Use of dioxane envelope to bring water insoluble cliromophores (chlorophylls) into contact with aqueous silver colloids for SERS enliancement. PSERRS— protected surface-enhanced resonance Raman spectroscopy . 

Kneipp K, Kneipp H, Deinum G, Itzkan I, Dasari R R and Feld M S 1998 Single-molecule detection of a cyanine dye in silver colloidal solution using near-infrared surface-enhanced Raman scattering App/. Spectrosc. 52 175-8... 

Collimation Collimators (+)-CoUinusin S. collinus Tb 365 Colloidal particles Colloidal silica Colloidal silver Colloidal state Colloidal sulfur Colloid mills Colloids... 

Figure 6. Successive UV-vis spectra (1 min time interval) of 4-nitrophenol using (a) GME and (b) FGME of silver colloids. (Reprinted from Ref. [46], 2001, with permission from American Chemical Society.)...

Silver/Colloidal Silver (Ag+). Silver has a slow inhibiting effect on bacterial and algicidal growth. It is a very expensive treatment and certainly not cost effective. If the silver or colloidal silver is not stabilized, it is not compatible with quats and polyquats. It will react with the chlorides of the quats. 

Tran [391,392] has reported ng detection of dyes on filter paper by SERS. Silver colloidal hydrosols stabilised by filter supports enhance the Raman scattering of adsorbed dyes. Typical detection limits are 500 pg (crystal violet), 7 ng (l,l,9-trimethyl-2,2 -cyanine perchlorate), 15 ng (3,3 -diethylthiacarbocyanine chloride) and 240 ng (methyl red) using a 3 mW He-Ne laser. 

Chen YH, Yeh CS (2001) A new approach for the formation of alloy nanoparticles laser synthesis of gold-silver alloy from gold-silver colloidal mixtures. Chem Commun 371-372... 

The use of ultrasound in both the synthesis and crystallisation of a broad array of both organic and inorganic materials has been intensively researched and is well documented [61-64]. An application of ultrasound that has received relatively less attention however, is in the dissolution of colloidal particles. Prakash and Ghosh [65] reported on the dissolution of silver colloids under 1 MHz ultrasound irradiation, proposing that the silver is oxidised by sonochemically produced hydroxyl radicals. Sostaric et al. [66] investigated the dissolution of MnC>2 colloids in the presence of aliphatic alcohols at a lower frequency of 20 kHz. They found that... 

SERS-active suspensions of elemental metal colloids or nanoparticles of various sizes can be chemically formed in solution. Silver colloids can easily... 

Sheng R.S., Zhu L., Morris, M.D., Sedimentation classification of silver colloids for surface-enhanced Raman-scattering, Anal. Chem. 1986 58 1116-1119. 

Ostuni E, Yan L, Whitesides GM (1999) The interaction of proteins and cells with self-assembled monolayers of alkanethiolates on gold and silver. Colloids Surf B 15 3-30... 

Lukomska J, Malicka J, Gryczynski I, Lakowicz JR (2004) Fluorescence enhancements on silver colloid coated surfaces. J Fluoresc 14 417 -23... 

UPD process has also been studied on screen-printed silver electrodes using voltammetric techniques and scanning electron microscope analysis [293]. The relative occurrence of UPD and bulk Pb process has been dependent on the scan rate, with increasing role of UPD process in higher rates. Studies on Pb deposition on silver colloids have pointed to its similarity to bulk electrode [283]. 

UPD of Ag onto Au electrodes covered with SAM of alkanethiols has been described by Oyamatsu [319]. Hu et al. [320] have prepared nanoelectrode ensembles by assembling silver colloid and mercaptan on a gold electrode. 

Fig. 9.2.17 Development of particle size during the formation in EG of monodisperse PVP-protected silver colloids. (From Ref. 39.)...

The silver ions used in the bacterial snsceptibility tests were released from pure silver electrodes using a 12 V battery-operated direct cnrrent generator. The apparatus used for silver ion generation was described previonsly in [13]. The water-based silver colloidal solution was obtained by a three-stage process based on the... 

Water paints were impregnated with nanosized silver colloids. Most of initial silver nanoparticles agglomerated into up to 200-nm clusters as a result of attractive interaction forces between the particles (Fig. 18.2). 

Cotton fabrics were impregnated with nanosized silver colloids synthesized by the electrochemical technique. The particles had good dispersibility on the surface of... 

These metal and metal oxide catalysts must work as a kind of electron pool which brings about multi-electron process for H2 and 02 generation. Silver colloids were studied as electron pool for H2 formation under y-irradiation in the aqueous system composed of Ag° colloids, acetone, 2-propanol and SDS S9). The colloids (average diameter 140 A) of 2.5 x 10 4 M can store 1 coulomb/1, corresponding to the storage of 450 electrons/particle 60 ... 

The assembly of silver colloids has proven to be a favorite subject of investigations [47, 509,510], due, in the main part, to the availability of detailed... 

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)... 

The excess negative charge located in the interior of metallic silver colloids could also be transferred to other electron acceptors, including methylviologen, nitrobenzene, nitropyridinium oxide, anthracene quinone sulfonic add, and potassium cyanohexaferrate(III)[506, 531], The efficiency and, indeed, the direction of electron transfer were found to depend on the position of the Fermi level of the surface-modified silver particles. For example, chemisorption of AgN to a silver particle is shown to result in a shift of the Fermi level to a more positive potential, as shown in the lower line in Fig. 84. 

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... 

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