Colloidal nanoparticles coated surfaces

Using this method to form a nanoparticle coated surface allowed us to better control the size of the nanostructures, but still generated a random distribution of nanoparticles. The density of silver nanostructures could be controlled by both the amount of time the substrate was immersed in the colloidal solution and the concentration of the colloidal solution. Because the size of the metal structures is directly determined by the colloids, sparse to densely packed colloid coated surfaces that maintain a unique metal nanostructure size could be produced by simply varying the incubation time in the colloid solution. 

Figure C 1.5.6. Single Ag nanoparticles imaged with evanescent-wave excitation. (A) Unfiltered photograph showing scattered laser light (514.5 nm) from Ag particles immobilized on a polylysine-coated surface. (B) Bandpass filtered (540-580 nm) photograph taken from a blank Ag colloid sample incubated witli 1 mM NaCl and...

Atomic beams, 31 Nanoparticles, 31 Force microsopy on coated surfaces, 31 Glass surfaces, 31 Mica, 32 Bilayers as thin films and as vesicles, 32 Cells and colloids, 33 Aerosols, 34 Bright stuff. Sonoluminescence, 34 Fun stuff, 34 Slippery stuff, ice and water, 34 What about interfacial energies and energies of cohesion Aren t van der Waals forces important there too, not just between bodies at a distance 35... 

The assembly was initially performed for Au Si02 with very thin shells (ca. 2 nm) on 640 nm polystyrene spheres [19] and later extended for latex cores of various sizes and gold nanoparticles coated with thicker shells. Examples of nanostructured colloids formed by assembly of Au Si02 with identical cores but silica shells with various thickness are shown in Fig. 7. It is clear that, although the surface of the particles is rough, the resultant layers are very compact... 

Ferrofluids synthesized by chemical coprecipitation may be surfactant-stabilized ferrofluids or ionic ferrofluids. Surfactant ferrofluids are iron oxide nanoparticles coated by stabilizers or surfactant layer(s) for colloidal stability. The coating agents are polymers and surfactants, be they polar, non-polar or non-ionic. Fatty acid derivatives are most often used to stabilize these iron oxide nanoparticles either in organic or aqueous medium. If the particles are dispersed in an aqueous medium, a double layer of surfactant is needed to form a hydrophilic layer. On the other hand, if the particles are dispersed in an organic non-polar medium, one layer of surfactant forms a hydrophobic layer on the surface of the particles. 

Here, we consider the two general approaches to coat colloidal particles with ultrathin film tunable in nanometer range. These methods differ by class of species employed for shell buildup, type of used colloidal particles and conditions for shell fabrication. First one is layer-by-layer (LbL) assembly of oppositely charged macromolecules or nanoparticles, which emanates from LbL assembly on macroscopic flat films developed in the early nineties by Decher and co-workers. Another approach is controlled precipitation of macromolecules or nanoparticles from the solution on surface of micron and submicron sized colloidal particles. The surfaces of these particles serves as collector for precipitating materials. 

Wang, Z.F., Xiao, P.F., Shen, B. and He, N.Y. (2006) Synthesis of palladium-coated magnetic nanoparticle and its application in Heck reaction. Colloids and Surfaces A Physicochemical and Engineering Aspects, 276 (1-3), 116-121. 

Polyacrylic nanoparticles have been prepared to investigate their use as colloidal drug carriers, and surface area measurements were used for characterization [14], When the experimental surface area values were compared with calculated values, it was found that the measured surface area value was 10 times smaller than the calculated value. The discrepancy was explained by the surfactant used in the nanoparticle preparation. The surfactant appears to coat the particles when it is not completely removed, resulting in the low surface areas observed for the particles. Particles prepared without surfactant showed good agreement with the calculated values. 

The Stober method can be used to form core-shell silica nanoparticles when a presynthesized core is suspended in a water-alcohol mixture. The core can be a silica nanoparticle or other types of nanomaterials [46, 47]. If the core is a silica nanoparticle, before adding silicon alkoxide precursors, the hydroxysilicates hydrolyzed from precursors condense by the hydroxide groups on the surface of the silica cores to form additional layers. If the core is a colloid, surface modification of the core might be necessary. For example, a gold colloid core was modified by poly (vinylpyrrolidone) prior to a silica layer coating [46]. 

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