Adsorption onto silver

Heard S.M., Grieser E., Barraclough C.G., Sanders J.V. Surface-enhanced Raman scattering as a means of studying competitive adsorption onto silver colloids. J. Phys. Chem. 1985 89(3) 389-396... 

Surface heterogeneity may be inferred from emission studies such as those studies by de Schrijver and co-workers on P and on R adsorbed on clay minerals [197,198]. In the case of adsorbed pyrene and its derivatives, there is considerable evidence for surface mobility (on clays, metal oxides, sulfides), as from the work of Thomas [199], de Mayo and co-workers [200], Singer [201] and Stahlberg et al. [202]. There has also been evidence for ground-state bimolecular association of adsorbed pyrene [66,203]. The sensitivity of pyrene to the polarity of its environment allows its use as a probe of surface polarity [204,205]. Pyrene or ofter emitters may be used as probes to study the structure of an adsorbate film, as in the case of Triton X-100 on silica [206], sodium dodecyl sulfate at the alumina surface [207] and hexadecyltrimethylammonium chloride adsorbed onto silver electrodes from water and dimethylformamide [208]. In all cases progressive structural changes were concluded to occur with increasing surfactant adsorption. 

Remove unreacted N-acetyl homocysteine thiolactone and reaction by-products by gel filtration or dialysis against lOmM sodium phosphate, 0.15M NaCl, lOmM EDTA, pH 7.2. Other buffers suitable for individual protein stability may be used as desired. For the silver nitrate-containing reaction, removal of the silver-thiourea complex may be done by adsorption onto Dowex 50, and the protein subsequently eluted from the resin by 1M thiourea. Removal of the thiourea then may be done by gel filtration or dialysis. 

We have previously employed such techniques in the study of iodide adsorption onto Pt(lll) electrodes (2 5 > as well as in the in-situ structural characterization of underpotentially deposited copper and silver on Au(lll) electrodes. (23.)... 

Fig. 13.2 Schematic representation of the process required to achieve detection of labeled DNA by SERRS. Represented is (a) an oligonucletide labeled with R6G which is already positively charged, therefore no surface modification is required to allow adsorption onto a silver nanoparticle surface and excited with laser light to give a SERRS spectrum and (b) an oligonucleotide modified with a negatively charged dye label, in this case HEX, which requires further modification of the DNA with propargylamine to introduce a region of positive charge to allow adsorption to the metal nanoparticle...

As discussed in Sections 2.4 and 2.5.4, the spectral contrast can be increased using MIR-OTEs. This approach has been used, for example, in the ATR studies of adsorption of lipid bilayers to Au [481], p-nitrobenzoic acid on Ag and Au [482] and electrochemical reactions on Au [434], Cu [483], steel [484], Pt [485], and iron [486] electrodes. The ATR technique with a Si MIRE covered by Ag and Au films was applied to the study of thiocyanate adsorption on silver and gold [487]. Enhanced SNR has been reported for the MIR in situ spectra of proteins adsorbed onto a Cu-coated cylindrical internal reflection element [488]. Since the optical path of the beam through a MIR OTE strongly depends on the wavelength, optical schemes with a fixed incident beam are not applicable in this case [362],... 

In PPV films deposited onto silver substrate, parallel chainlike features were reported, with larger separation (typically 1.8 nm) than expected from the interchain unit cell [132]. This was observed independently of polymer film thickness and material used as substrate and was tentative attributed to some surface reconstruction, possibly due to adsorption of oxygen. Polarization-dependent photoabsorption measurements made in PPV mono-layers prepared by the Langmuir-Blodgett precursor technique onto Mo 2 substrate showed that the phenylene and vinylene moieties are nearly parallel to the surface [125]. 

Although SERS is inherently a very selective technique, Carrabba et al. [72] have used electrosorption of analytes onto silver electrodes to further increase the analytical selectivity of SERS for the identification of structurally similar compounds. By changing the potential of the electrode, the SERS spectrum was noted to change differently for all chemicals investigated. This is based on the fact that the chemically specific free energy of adsorption is changed as the electrode potential is varied, which gives rise to potential-dependent peak positions and intensities for individual compounds. 

The potential dependence of ethyl xanthate coverage has also been determined for silver-gold alloys. In this system, xanthate chemisorbs onto silver sites in the alloy surface, and, as with silver itself, adsorption occurs at potentials below that at which silver xanthate is formed. Figure 11 presents the coverages determined for this system. The solid lines represent the Frumkin isotherm previously derived for silver. The isotherms for the alloys were obtained by introducing a silver activity term, taking values of activity derived from the thermodynamic data collated by... 

Figure 1. Schematic illustration of several of the lattices formed by the adsorption of sulfur-containing species onto gold and silver. In diese figures, the small, open circles represent metal atoms in the (111) plane, black circles define the unit cell of sulfur atoms, and my circles represent other sulfur atoms within die unit cell, (a) The ( f3xV3)R30° lattice formed by the adsorption of long-chain alk ethiols onto gold (17,20) the surface species in this structure is RS"Au(I) (15,22). The area per sulfur atom is 21.5 A. (b) Incommensurate lattice formed by the adsorption of octadecanethiol onto silver (31) the surface species is...

Studies from this laboratory 24-27 suggest that a sulfur atom is effective to immobilize promoters by irreversible adsorption onto gold and silver electrodes. To date, various sulfur containing promoters are known to give effective promoter-modified electrodes for cytochrome c. In the present paper, surface structures of such promoter-modified electrodes and electrochemistry of cytochrome c at these electrodes have been investigated to better understand the surface functions of such electrodes. 

This author points out that Sols prepared with different stabilizers often have quite different absorption spectra even though the particle size distributions appear similar. This statement could readily be applied to our sols. The adsorption of iodide or sulfide ions [20] or of stabilizers such as gelatin or poly(vinyl pyrrolidone (PVP) [21-23] onto silver colloids led to a marked red shift, with damping of the plasmon band. The same phenomena were observed in this study experimentally as blue and red shifts of the plasmon maximum peak. The observed red shift, associated with the addition of surfactant stabilizers, is due to the displacement of nucleophiles (i.e., anions adsorbed on the particle surface) by the surfactants from the surface. 

Robertson [ 57 ] has measured the adsorption of zinc, caesium, strontium, antimony, indium, iron, silver, copper, cobalt, rubidium, scandium, and uranium onto glass and polyethylene containers. Radioactive forms of these elements were added to samples of seawater, the samples were adjusted to the original pH of 8.0, and aliquots were poured into polyethylene bottles, Pyrex-glass bottles and polyethylene bottles contained 1 ml concentrated hydrochloric acid to bring the pH to about 1.5. Adsorption on the containers was observed for storage periods of up to 75 d with the use of a Nal(Tl) well crystal. Negligible adsorption on all containers was registered for zinc, caesium, strontium, and... 

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