Monodispersed colloids

The topic of gold nanospheres attracted the interest of several famous nineteenth century scientists such as Michael Faraday, Richard Zsigmondy, and Gustov Mie [43]. Interest diminished in the mid-twentieth century although some excellent contributions were made by Turkevich [42, 44], Frens [45], and Brust [46] in that period regarding the controlled preparation of nearly monodisperse colloidal suspensions. 

Nyffenegger, R., Quellet, C., and Rieka, J. (1993) Synthesis of fluorescent, monodisperse, colloidal silica particles./. Colloid Interface Sci. 159, 150-157. 

Colloids are larger molecular weight solutions (more than 30,000 daltons) that have been recommended for use in conjunction with or as replacements for crystalloid solutions. Albumin is a monodisperse colloid because all of its molecules are of the same molecular weight, whereas hetastarch and dextran solutions are polydisperse compounds with molecules of varying molecular weights. 

There are several bottom-up methods for the preparation of nanoparticles and also colloidal nanometals. Amongst these, the salt-reduction method is one of the most powerful in obtaining monodisperse colloidal particles. Electrochemical methods, which gained prominence recently after the days of Faraday, are not used to prepare colloidal nanoparticles on a large scale [26, 46], The decomposition of lower valent transitional metal complexes is gaining momentum in recent years for the production of uniform particle size nanoparticles in multigram amounts [47,48],... 

Heterodisperse Suspensions. The rate laws given above apply to monodisperse colloids. In polydisperse systems the particle size and the distribution of particle sizes have pronounced effects on the kinetics of agglomeration (O Melia, 1978). For the various transport mechanisms (Brownian diffusion, fluid shear, and differential settling), the rates at which particles come into contact are given in Table 7.2. 

DR. RAMESH PATEL (Clarkson College) It appears that studies on colloidal systems may represent an extremely important area for the future. We have also been doing some colloidal work, particularly dealing with the solution chemistry that precedes the formation of very highly monodispersed colloidal particles. One such system with iron phosphate has been included in the poster presentation. 

E. Matijevic, Preparation and properties of monodispersed colloidal metal hydrous oxides. Pure Appl. Chem. 50(9-10), 1193-1210 (1978). 

Any study of colloidal crystals requires the preparation of monodisperse colloidal particles that are uniform in size, shape, composition, and surface properties. Monodisperse spherical colloids of various sizes, composition, and surface properties have been prepared via numerous synthetic strategies [67]. However, the direct preparation of crystal phases from spherical particles usually leads to a rather limited set of close-packed structures (hexagonal close packed, face-centered cubic, or body-centered cubic structures). Relatively few studies exist on the preparation of monodisperse nonspherical colloids. In general, direct synthetic methods are restricted to particles with simple shapes such as rods, spheroids, or plates [68]. An alternative route for the preparation of uniform particles with a more complex structure might consist of the formation of discrete uniform aggregates of self-organized spherical particles. The use of colloidal clusters with a given number of particles, with controlled shape and dimension, could lead to colloidal crystals with unusual symmetries [69]. 

Y. Yin, Y. Lu, B. Gates, and Y. Xia Template-Assisted Self Assembly A Practical Route to Complex Aggregates of Monodispersed Colloids with Well-Defined Sizes, Shapes and Structures. J. Am. Chem. Soc. 123, 8718 (2001). 

The methods used to prepare monodisperse colloids aim to achieve a large number of critical nuclei in a short interval of time. This induces all equally sized nuclei to grow simultaneously, thus producing a monodisperse colloidal product. 

Matijevic, E. Partsch, R.E. (2000) Synthesis of monodispersed colloids by chemical reactions. In Sugimoto.T. (ed.) Fine Particles Synthesis, Characterization and Mechanism of Growth. Marcel Dekker, New York Matijevic, E. Sapieszko, R.S. (2000) Forced hydrolysis in homogeneous solutions. In Sugi-moto, T. (ed.) Fine Particles. Basel, Marcel Dekker, 2-34... 

Dtsch. Bodenkl. Gesell. 59/1 505—510 Zelenev, A. Matijevic, E. (1997) Effect of surfactants on particle adhesion. Part I Interactions of monodisperse colloidal hematite particles with glass beads in the presence of sodium 4-octyl benzene sulphonate. Coll. ... 

Colloidosomes are a recent class of microcapsules and thus far have only been applied to catalysis and drug delivery in a few cases. The term colloidosomes was coined by Anthony Dinsmore and colleagues in 2002 to refer to capsules where the shells are composed of close-packed layers of monodisperse colloidal particles (usually micron-sized polymer beads) that have been linked together by sintering. 

Boutonnet M, Kizling J, Stenius P (1982) The Preparation of Monodisperse Colloidal Metal Particles from Micro-Emulsions. Colloids Surf 5 209-225... 

This chapter summarizes the present state of the art of the forced hydrolysis approach by considering specific cations, particularly those of greatest practical and theoretical interest, using aqueous solutions of common salts. In addition to being economical in the manufacture of different products, the described procedure can also help in the development of a better understanding of different processes, such as corrosion of metals or formation of minerals, to mention a few. It should be emphasized that the focus of this chapter is on dispersions of narrow particle size distributions, normally designated as monodispersed systems. While a number of genera reviews have been published on monodispersed colloids (7,9-21), this chapter specifically addresses the problems related to metal (hydrous) oxides. 

It took almost a century from the time Faraday obtained the first monodispersed colloid, his well-known gold sol (22), until the works of Steele (l) and Heller (2,3) mentioned earlier. Therefore, it is even more surprising that all one needs to obtain... 

Fig. 1.1.2 Schematic presentation of the plug-flow type of a reactor for the continuous preparation of monodispersed colloids by precipitation from homogeneous solutions. (From Ref. 31.)...

In discussing the mechanisms of the formation of monodispersed colloids by precipitation in homogeneous solutions, it is necessary to consider both the chemical and physical aspects of the processes involved. The former require information on the composition of all species in solution, and especially of those that directly lead to the solid phase formation, while the latter deal with the nucleation, particle growth, and/or aggregation stages of the systems under investigation. In both instances, the kinetics of these processes play an essential role in defining the properties of the final products. 

Fig. 1.1.4 The original reaction scheme for the formation of monodispersed colloids as proposed by LaMer.

SYNTHESIS OF MONODISPERSED COLLOIDS BY CHEMICAL REACTIONS IN AEROSOLS... 

Fig. 9.2.11 TEM images of monodisperse colloidal dispersions prepared by heterogeneous nucleation with Pt as nucleating agent (A) Co15Ni6, dm = 50 nm, cr = 0.10dm. (B) Co8oNi2o, dm = 7 nm,

Modifications of monodisperse colloidal silica, of 10 or 500 nm in diameter, were carried out using trialkoxysilane-terminated polymer in a low polar solvent, such as acetone or 1,2-dimethoxyethane. without coagulation during the coupling reaction (35,37-42). In this modification, the hydrophobic polymer can be efficiently bound to hydrophilic colloidal silica surface. The reaction mechanism of the binding... 

Fig. 12.1.2 Absorbance changes of the suspension (0.1 wt%) containing monodisperse colloidal silica modified with irontlll-bipyridyl-branched poly((V-isopropylacrylamide). (From Ref. 50.)...

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