Single colloidal properties

This latter support was based on the then accepted idea that the molecule could not be larger than the unit cell of the crystal. In addition, supporters noted that the colloidal properties of many substances such as soaps are based on the creation of large aggregates of small single molecules. 

Many approaches have been taken to prepare colloidal doped semiconductor nanocrystals. For example, hot-injection methods have been used to synthesize colloidal Mn2+-doped CdSe (47, 48), ZnSe (49), and PbSe (50) colloidal nanocrystals. Colloidal ZnO DMS-QDs doped with Co2+, Ni2+, and Mn2+ have been prepared by low-temperature hydrolysis and condensation (51-54). Sol-gel methods have been used to prepare colloidal doped TiC>2 (55-57) and Sn02 (58-62) nanocrystals. Inverted micelle methods have been used for preparation of a range of doped II-VI sulfide DMS-QDs at low temperatures (63-68). A high-temperature lyothermal single-source method was used to synthesize Co2+- and Eu3+-doped CdSe nanocrystals (69, 70). Autoclaving has occasionally been used to induce crystallization at lower temperatures than reached under atmospheric pressures while retaining colloidal properties, for... 

In this chapter, we have described the colloid chemistiy of ceramic powders in suspension. Colloid stability is manipulated by electrostatic and steric means. The ramifications on processing have been discussed with emphasis on single-phase ceramic suspensions with a distribution of particle sizes and composites and their problems of component segregation due to density and particle size and shape. The next chapter will discuss the rheology of Uie ceramic suspensions and the mechanical behavior of dry ceramic powders to prepare the ground for ceramic green body formation. The rheology of ceramic suspensions depends on their colloidal properties. 

In the next main division the different kinds of single colloid systems will be treated. Here once more solutions are dealt with as a subdivision, but now the stress is laid on the actual properties of the whole system, including interactions between macromolecular ions among themselves or macromolecular ions and micro ions. 

The difference between the two kinds of colloid systems resides in the equilibrium character of the true single colloid systems " and the non-equilibrium character of the "apparent single colloid systems . Considered from the two-phase standpoint, the mutual surface of contact between the colloid-rich and the colloid-poor phase is very great in these latter systems, so that they attempt to reduce this surface of contact. They will therefore chaise their properties with time while the true single systems do not change with time. 

This chapter provides a brief introduction to the fundamentals in colloid science. It addresses the physico-chemical properties of single colloidal particles as well as the processes at the interface and the structure of the interfacial layer. It further examines the non-viscous interactions that occur among colloidal particles. For detailed explanation, the reader is referred to the textbooks of Adamson and Gast (1997), Hunter (1988, 1993), Lyklema (1991, 1995, 2000), or Israelachvili (1992). 

The concept of surfactant self-assembly is revisited in the organic laboratory. A manuscript detailing this experiment has been submitted elsewhere (55), and is briefly sununarized here. In a single laboratory session, students synthesize and investigate the colloidal properties of a gemini surfactant - an amphiphiUc molecule with two non-polar tails and two polar heads eoimected by a spacer (see Figure 2a) (34, 55). The synthesis (a double Menshutkin reaction) and purification are straightforward and reproducible by oi nie lab students. 

Bolhuis and Frenkel are interested in simulating the properties of colloidal solutions. Examples of such solutions are milk, paint, or mayonnaise. Since a single colloidal particle may contain over 10 atoms it is not possible to model such a particle as a collection of atoms. However, it is possible to describe colloidal solutions using coarse-grained models. For example, a suspension of silica spheres can be described surprisingly accurately with a hard-sphere potential. Similarly to the hard-sphere fluid, such a colloidal suspension has a fluid-solid transition, but not a liquid-gas transition. Experimentally, it is observed that a liquid-gas transition can be induced by adding polymers to the suspension. 

One of the models best able to describe the properties of micellar colloid solutions is the closed-association model. In it, we start by assuming the colloid comprises n molecules of monomer. We approximate by saying the colloid forms during a single step ... 

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