Colloids aqueous colloidal solutions

Bead Polymerization Bulk reaction proceeds in independent droplets of 10 to 1,000 [Lm diameter suspended in water or other medium and insulated from each other by some colloid. A typical suspending agent is polyvinyl alcohol dissolved in water. The polymerization can be done to high conversion. Temperature control is easy because of the moderating thermal effect of the water and its low viscosity. The suspensions sometimes are unstable and agitation may be critical. Only batch reaciors appear to be in industrial use polyvinyl acetate in methanol, copolymers of acrylates and methacrylates, polyacrylonitrile in aqueous ZnCh solution, and others. Bead polymerization of styrene takes 8 to 12 h. 

In order to obtain Pt nanoparticles, aqueous solution of 10 M K2PtCl4, which contained 10 M (as monomer unit) of poly-NIPA or poly-NEA, was bubbled with Ar gas and then H2 gas. Then the reaction vessel was sealed tightly and kept in a water bath at a suitable temperature. At given reaction times, the vessels were opened and the samples for transmission electron microscopy (TEM) were prepared by soaking a grid (carbon substrate, Oken) in the colloidal solution and then drying it in the air. The TEM (Hitachi H-8100) was operated at 200 kV. 

T. Austad, B. Matre, J. Milter, A. Saevareid, and L. Oyno. Chemical flooding of oil reservoirs Pt 8 Spontaneous oil expulsion from oil-and water-wet low permeable chalk material by imbibition of aqueous surfactant solutions. Colloids Surfaces, Sect A, 137(1-3) 117-129, 1998. 

In the study of effects of ultrasound on the aqueous reactions of nickel, we found some interesting results, for example, the colloidal formation of Ni-DMG complex and degassing of NH3 during different experiments. When 25 ml of 0.001 M NiSC>4 solution was complexed with 5 ml of 1% dimethyl glyoxime (DMG) in faintly alkaline ammonia medium and sonicated for 30 minutes and compared with another set of 25 ml of complexed solution which was stirred mechanically, a colloidal solution of Ni-DMG complex was formed in sonicated condition. Particles of Ni-DMG complex did not settle even after keeping 3 1 h because of their smaller size, in sonicated solution, whereas in the unsonicated condition large particles of Ni-DMG complex settled down immediately. 

Akers W, Haidekker MA (2004) A molecular rotor as viscosity sensor in aqueous colloid solutions. J Biomech Eng 126(3) 340-345... 

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. 

Colloidal Stability of Microcrystailine Cellulose in Aqueous Salt Solutions... 

Figure 10.4. (a) Schematic energy diagrams of clusters, nanoparticles, and bulk semiconductors. (b) Manifestation of the size quantization effect as a color change of aqueous colloidal solutions of CdSe nanoparticles (courtesy of A. Rogach). The particle size changes from left to right from -1.5 to -4.5 nm. (c) Bulk CdSe crystal. (See color insert.)... 

Surfactants are well known as stabilizers in the preparation of metal nanoparticles for catalysis in water. Micelles constitute interesting nanoreactors for the synthesis of controlled-size nanoparticles from metal salts due to the confinement of the particles inside the micelle cores. Aqueous colloidal solutions are then obtained which can be easily used as catalysts. 

Andrievsky GV, Kosevich MV, Vovk OM et al. (1995) On the production of an aqueous colloidal solution of fullerene. J Chem Soc Chem Commun. 1281-1282. 

The term biocolloids or biosolids is frequently applied to microbes in solution. Bacteria, algae, protozoans, and many other biological agents present in the aqueous phase can be considered to exhibit colloidal behavior [114-124]. Insofar as these species are able to sorb pollutants like other colloids, the distinction between living and nonliving colloids is relatively unimportant. It is also known that biological exudates or subcellular fragments may exist in colloidal solution [124]. 

The solubility of paclitaxel in water at 25°C at pH 7.4 is 0.172mg/L (0.2 pM), extremely low, making any separation procedure of nonencapsulated paclitaxel from DQAsomes unnecessary i.e., in an aqueous environment, only paclitaxel encapsulated in DQAsomes would stay in colloidal solution. However, for control, a paclitaxel suspension was probe sonicated under identical conditions used for the encapsulation of paclitaxel into DQAsomes, but in the complete absence of dequalinium chloride. As expected, upon centrifugation, no paclitaxel was detectable in the supernatant using ultraviolet (UV) spectroscopy at 230 nm. 

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