Colloidal organic particles

Electron transfer processes leading to a product adsorbed in the interfacial region o are of practical interest. These processes include the deposition of a metal such as Cu or Pd at ITIES, the preparation of colloidal metal particles with catalytic properties for homogeneous organic reactions, or electropolymerization. 

Living Colloidal Metal Particles from Solvated Metal Atoms Clustering of Metal Atoms in Organic Media... 

A review of preparative methods for metal sols (colloidal metal particles) suspended in solution is given. The problems involved with the preparation and stabilization of non-aqueous metal colloidal particles are noted. A new method is described for preparing non-aqueous metal sols based on the clustering of solvated metal atoms (from metal vaporization) in cold organic solvents. Gold-acetone colloidal solutions are discussed in detail, especially their preparation, control of particle size (2-9 nm), electrophoresis measurements, electron microscopy, GC-MS, resistivity, and related studies. Particle stabilization involves both electrostatic and steric mechanisms and these are discussed in comparison with aqueous systems. 

Taken together, the experimental observations reported in the previous sections suggest that the formation of colloidally stable particles heated above their phase-transition temperature may be a universal phenomenon, taking place not only in aqueous polymer solutions, but also in solutions of polymers that can undergo a coil-globule transition in organic solvents. 

Figure 6.1. Species around soil particles. CC, day colloid COM, colloidal organic matter. 

Photoredox processes with colloidal semiconductor particles as photo-catalyst, e.g. degradation of refractory organic substances... 

In a qualitative way, colloids are stable when they are electrically charged (we will not consider here the stability of hydrophilic colloids - gelatine, starch, proteins, macromolecules, biocolloids - where stability may be enhanced by steric arrangements and the affinity of organic functional groups to water). In a physical model of colloid stability particle repulsion due to electrostatic interaction is counteracted by attraction due to van der Waal interaction. The repulsion energy depends on the surface potential and its decrease in the diffuse part of the double layer the decay of the potential with distance is a function of the ionic strength (Fig. 3.2c and Fig. 

Spray drying requires formulahon of a relatively stable, usually aqueous dispersion of zeolite and colloidal binder particles, which are then fed to the spray drier [88, 89], Organic dispersing agents may be added to the spray drier feed slurry to stabilize the dispersion while the slurry is fed to the drier. 

Transport of contaminants by surface runoff is illustrated in the experimental results of Turner et al. (2004), which deal with the colloid-mediated transfer of phosphorus (P) from a calcareous agricultural land to watercourses. Colloidal molybdate-reactive phosphorus (MRP) was identified by ultrafiltration associated with particles between l am and Inm in diameter. Colloidal P compounds can constitute a substantial component of the filterable MRP in soil solution and include primary and secondary P minerals, P occluded or adsorbed on or within mineral or organic particles, and biocolloids (Kretzschmar et al. 1999). 

Metal labels have been proposed to resolve problems connected with enzymes. Metal ions [13-16], metal-containing organic compounds [17,18], metal complexes [19-21], metalloproteins or colloidal metal particles [22-28] have served as labels. Spectrophotometric [22,25], acoustic [25], surface plasmon resonance, infrared [24] and Raman spectroscopic [28] methods, etc. were used. A few papers have been dealing with electrochemical detection. However, electrochemical methods of metal label detection may be viewed as very promising taking into account their high sensitivity, low detection limit, selectivity, simplicity, low cost and the availability of portable instruments. 

Colloids. Colloids include particles with hydrophobic, hydrophilic and intermediate forms with a size range 1 - 400 nm. Both organic (including macromolecules) and inorganic (hydrolyzed silica and metal oxides) colloids occur in the marine environment (Sigleo and Helz, 1981). Their surfaces often contain suitable sites for interactions with trace metals (adsorption, complexation). In the marine environment all particles have a negative surface charge (Neihof and Loeb, 1972 Hunter and Liss, 1982). Increase of the electrolyte concentration decreases the stability of the colloidal particles. As a result the... 

A broad variety of sacrificial colloidal cores have been used for hollow capsule fabrication. They are inorganic or organic particles from tens of nanometers and up to tens of micrometerss, like melamine formaldehyde (MF), polysterene spheres, CaCC>3 and MgCQ3 particles, protein and DNA aggregates, small dye... 

Coagulation processes in estuaries are affected by other factors such as clay composition, particle size, and concentration of dissolved organic matter, to mention a few. For example, early work has shown that metal hydroxides can flocculate from dis-solved/colloidal organic matter during the mixing of river-derived iron and seawater in the mixing zone of estuaries (Sholkovitz, 1976, 1978 Boyle et al, 1977 Mayer, 1982) (more details are provided on metal colloidal interactions in chapter 14). Surface sediments in... 

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