Gold substrates

The solder and ahoy market, including low melting or fusible ahoys, is a principal user of indium (see SoLDERS AND BRAZING ALLOYS). The addition of indium results in unique properties of solders such as improved corrosion and fatigue resistance, increased hardness, and compatibhity with gold substrates. To fachitate use in various appHcations, indium and its ahoys can be easily fabricated into wine, ribbon, foil, spheres, preforms, solder paste, and powder. 

Fig. 11. RAIR spectrum of 4-MPP adsorbed onto a gold substrate. Reproduced by permission of the American Chemical Society from Ref. [9].

Duncan and Frankenthal report on the effect of pH on the corrosion rate of gold in sulphate solutions in terms of the polarization curves. It was found that the rate of anodic dissolution is independent of pH in such solutions and that the rate controlling mechanism for anodic film formation and oxygen evolution are the same. For the open circuit behaviour of ferric oxide films on a gold substrate in sodium chloride solutions containing low iron concentration it is found that the film oxide is readily transformed to a lower oxidation state with a Fe /Fe ratio corresponding to that of magnetite . 

When particles are arranged in an FCC structure, as shown in Figure 3, the I V) curve shows a linear ohmic behavior (Fig. 9C). The detected current, above the site point, markedly increases compared to data obtained with a monolayer made of nanocrystals (Fig. 9C). Of course, the dIldV(Y) curve is flat (inset Fig. 9C). This shows a metallic character without Coulomb blockade or staircases. There is an ohmic connection through multilayers of nanoparticles. This effect cannot be attributed to coalescence of nanocrystals on the gold substrate, for the following reasons ... 

Alanyahopu M, (Jakal H, Oztiirk AE, Demir U (2001) Electrochemical studies of the effects of pH and the surface stracture of gold substrates on the underpotential deposition of sulfur. J Phys Chem B 105 10588-10593... 

Ham S, Choi B, Paeng KJ, Myung N, Rajeshwar K (2007) Photoinduced cathodic deposition of CdTe nanoparticles on polycrystalline gold substrate. Electrochem Commun 9 1293-1297... 

Sulfiir-anchored SAMs and thin films, mostly from organosulfiir precursors, have been discussed at length by a number of authors [10, 181]. SAMs of organosulfiir compounds (thiols, disulfides, sulfides) form on gold substrates by spontaneous adsorption from either the liquid or the vapor phase. A number of experimental factors can affect the formation and structure of SAMs such as choice of solvent, temperature, concentration, immersion time, purity of adsorbate, oxygen concentration in solution, cleanliness, and structure of the adsorbate. Interestingly, the... 

Figure 16.5 Change of contact angle of nitrobenezene droplet. The droplet was put on a gold substrate covered with Fc-alkanethiols in a 1 M aqueous solution of HCIO4. Fc was neutral (a) and positively charged (b).

Friedrich KA, Henglein F, Slimming U, Unkauf W. 1998. Investigation of Pt particles on gold substrates by IR spectroscopy—Particle structure and catalytic activity. Colloids Surf A 134 193-206. 

Several precautions were taken to ensure the immobilization chemistry. First, the sulfhydryl groups containing the macromolecular fraction was spectrophotometrically determined according to the literature [15]. We found that every set of 150 base pairs contained approximately one disulfide group. Since the DNA fragment used has hundreds of base pairs, each DNA strand seems to have one disulfide as its terminal group. Next, we made IR spectral measurements in a reflection-absorption (RA) mode [14b]. A freshly evaporated gold substrate was immersed into the DNA solution for 24 h at 5°C. The substrate was carefully rinsed with deionized water, dried under vacuum and was immediately used for the measurements. An Au substrate treated with unmodified, native sonicated CT DNA solution was also prepared as the control measurement. The / -polar-ized radiation was introduced on the sample at 85° off the surface normal and data were collected at a spectral resolution of 4 cm with 2025 scans. 

FIG. 1 FT-IR spectra in midfrequency region. DNA-treated gold substrate measured in reflection-absorption mode (a) and transmittance spectrum of DNA cast on Cap2 (b). 

FIG. 4 FT-IRRAS spectrum in midfrequency region for gold substrate treated with 5 -TsTsTsTsTsTCTCATACATG-3. The i-polarized radiation was introduced on the sample at 85° off the surface normal and data were collected at a spectral resolution of 4 cm with 256 scans. 

The carboxylic acid functionality is not involved in any significant interaction with the gold substrate but rather dominates the pairing interaction between enantiomers. This three-point bonding of each molecule, Au—S, Au—N, and O—H—O, drives the self-recognition preference for homochiral pairs [58]. 

Ko WY, Chen WH, Tzeng SD et al (2006) Synthesis of pyramidal copper nanoparticles on gold substrate. Chem Mater 18 6097-6099... 

Liu YC, Kin LH, Chiu WH (2004) Size-controlled synthesis of gold nanoparticles from bulk gold substrates by sonoelectrochemical methods. J Phys Chem B 108 19237-19240... 

Zhong X, Yuan R, Chai Y, Liu Y, Dai J, Tang D (2005) Glucose biosensor based on self-assembled gold nanoparticles and double-layer 2d-network (3-mercaptopropyl)-trimethoxy-silane polymer onto gold substrate. Sensor Actuator B 104 191-198... 

Fu X.Y., Mu T., Wang J., Zhu T., Liu Z.F., pH-dependent assembling of gold nanoparticles on p- aminothiophenol modified gold substrate, Acta Physico-Chimica Sinica 1998 14 968-974. 

Zhu T., Yu H.Z., Wang J., Wang Y.Q., Cai S.M., Liu Z.F., Two-dimensional surface enhanced Raman mapping of differently prepared gold substrates with an azobenzene self-assembled monolayer, Chem. Phys. Lett. 1997 265 334-340. 

FIGURE 15.7 Synthesis of aligned SWNTs by the self-assembly of nanotubes end-functionalized with thiol groups on a gold substrate [51]. (Reprinted with permission from [51]. Copyright (2003) Wiley VCH Verlag GmbH Co. KG.)... 

Why do we believe that a Cu monolayer is inserted between SAM and gold substrate The 2D-deposit grows and dissolves extremely slowly. Another indication is that the 2D deposit is very stable and shows no displacement by the scanning tip. Cu clusters on top of an alkanethiol-SAM would be only weakly bound and should be easily pushed away by the tip at higher tunnel currents, very much like metal clusters on a hydrogen-terminated Si(lll) surface, which for that very reason are difficult to image by STM (or AFM [122]). And finally, the cyclic voltammograms (Fig. 33) point to the formation of a buried monolayer . 

Figure 12 Self assembled monolayer of TTF-based cation sensor on gold substrate (Redrawn from Moore et a/.114)...

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