Gold, colloidal polarization

This technique yields highly concentrated gold colloidal suspension with particle diameter in the range 5-10 nm. Colloid can be suspended in both polar and nonpolar solvents. 

Solvents such as organic liquids can act as stabilizers [204] for metal colloids, and in case of gold it was even reported that the donor properties of the medium determine the sign and the strength of the induced charge [205]. Also, in case of colloidal metal suspensions even in less polar solvents electrostatic stabilization effects have been assumed to arise from the donor properties of the respective liquid. Most common solvent stabilizations have been achieved with THF or propylenecarbonate. For example, smallsized clusters of zerovalent early transition metals Ti, Zr, V, Nb, and Mn have been stabilized by THF after [BEt3H ] reduction of the pre-formed THF adducts (Equation (6)) [54,55,59,206]. Table 1 summarizes the results. 

A report of a particle-based FPIA<56) details improvement in the limit of detection by two orders of magnitude over a conventional FPIA format for rabbit IgG, to 10 ° M. Goat anti-rabbit capture antibody (binder) is immobilized on polystyrene microspheres or colloidal gold particles, and the sample competes with a fluorescein-labeled rabbit IgG probe. The observed increase in sensitivity is apparently due to the large increase in effective mass of the binding complex. The polarization range is rather limited, though, reportedly due to low concentrations of immobilized antibodies. 

The study of colloidal crystals was initiated as part of research into the determination of phase diagrams for colloids, which itself was perceived as a means to model phase behaviour in molecular systems [22]. Extensive literature is available on the dynamics of colloidal crystal formation, as a function of several parameters, such as the nature of the solvent, surface charge, particle size and concentration. The results described here refer to the formation of colloidal crystals from dispersions of silica-coated gold nanoparticles in ethanol, after silica surface functionalization with 3-(trimethoxysilyl)propyl methacrylate (TPM). Earlier studies by Philipse and Vrij [23] showed that TPM adsorption leads to a reduction in surface charge, so that the particles are stable in organic solvents with low polarity, such as ethanol, toluene or DMF. This means that the particle be-... 

Manciu, M, and E, Ruckenstein, The polarization model for hydration/double layer interactions the role of the electrolyte ions. Advances in Colloid and Interface Science, 2004, 112(1-3) pp, 109-128 Turkevish, J, Gold Bull, 1985, 18 p, 86,... 

In Figure 51.3, the spectrum of colloidal silver before and after electron injection from a gold mesh electrode shows that cathodic polarization leads to a blue shift of the surface plasmon band. The particles initially had a redox potential of +0.15 V vs Ag/AgCl, whereas afterwards it was at —0.6 V. The charge transferred corresponded to a double layer capacitance of 80 microfarads cm. Femtosecond heating of the conduction electrons in small particles results in shifts in the surface plasmon band. Initial relaxation due to electron-lattice collisions takes... 

The colloidal assembly of gold nanorods presents an elegant demonstration of the polarization and orientation dependence of... 

Colloidal solutions of gold in different solvents have been one of the most intensively studied and well-understood systems. Polar solvents such as acetone, dimethylformamide, tetrahydrofuran... and nonpolar solvents such as toluene, hexane, cyclohexane, decane... were broadly used as reaction media or solvent-madiated media. Acetone, as a polar solvent, solvates the metal atoms and clusters during the warmup stage [23]. In this way steric stabilization is achieved and some metal colloids can be stable for months. This behavior is the main motivation for choosing polar solvent as an initial solvent or co-stabilizer. Generally, the additional stabilizing agent such as alkylamine, alkylthiol, or alkylalcohol is mostly needed for the stabilization of final metal fluid. As reported [24, 25], two types of stabilization are characteristic for these systems ... 

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