Characterization colloidally stable

Figure 7 illustrates the total interparticle potential, E, for colloidally stable systems and flocculated systems, where d is the particle diameter and r is the distance between the centers of two approaching particles. A colloidally stable suspension is characterized by a repulsive interaction (positive potential) when two particles approach each other (Figure 7a). Such a repulsion varies with distance, and hence it is termed soft repulsion. In the extreme, owing to the short range of the repulsive...

The alkaline EG S5mthesis method is a very effective technology for the chemical preparation of unprotected metal and alloy nanoclusters stabilized by EG and simple ions. This method is characterized by two steps involving the formation of metal hydroxide or oxide colloidal particles and the reduction of them by EG in a basic condition. The strategy of separating the core formation from reduction processes provides a valid route to overcome the obstacle in producing stable unprotected metal nanoclusters in colloidal solutions with high metal concentrations. Noble metal and alloy nanoclusters such as Pt, Rh, Ru, Os, Pt/Rh and Pt/Ru nanoclusters with small particle... 

However, there are a number of difficulties associated with the synthesis of colloidal semiconductor particles. The preparation of stable, monodispersed, well-characterized populations of nanosized, colloidal semiconductor particles is experimentally demanding and intellectually challenging. Small and uniform particles are needed to diminish non-productive electron-hole recombinations the mean distance by which the charge carriers need to diffuse to reach the particle surface from which they are released is necessarily reduced in small particles. Monodispersity is a requirement for the observation of many of the spectroscopic and electro-optical manifestations of size quantization in semiconductor particles. Small semiconductor particles are difficult to maintain in solution in the absence of stabilizers flocculations and Ostwald ripening... 

We have already defined the stability ratio operationally. A stable colloidal dispersion is characterized by a high-energy barrier, that is, by a net repulsive... 

Purification and characterizations of extracellular chitinases from the marine bacterium Bacillus sp. LJ-25 were described by Lee et al. (2000a). The purified chitinase so obtained showed a single band on SDS-PAGE and had an MW of approximately 50 kDa. The chitinase was most active and relatively stable at a pH of 7.0. The optimum temperature for this enzyme was around 35 °C when the pH of the reaction was kept at 7.0. The effect of metal ions on chitinase activity showed that Zn2+ strongly inhibited the enzyme activity. However, Ba2+, Co2+, Mn2+, and Cu2+ showed slight inhibition of the enzyme. Substrate specificity studies indicated that colloidal chitin (a substrate of the endo type of chitinase) was efficiently degraded by the chitinase. However, chitin and chitosan were ineffectively hydrolyzed by this enzyme. This chitinase did not hydrolyze /V,iV-diacetylchitobiose, j9-nitro phenol- /V- ace tyl - (3 -1 > - g I u c o s a mine, and Micrococcus lysodeikticus cells, which are known to be the substrates of the exo type of chitinases. 

---