Colloid stability technology

Moreover, the use of MIP microparticles with quantum dots (QDs) as signal transducers for the detection of nitroaromatic explosives has been very recently presented [71]. LOD for aqueous solutions was 30.1 pM and 40.7 pM for DNT and TNT, respectively. Although the LODs of the presented system are 100 times lower than those for other already developed TNT sensitive systems, this example presents a new interesting approach in the MIPs technology. If the colloidal stability and size distribution of the microparticles were improved, this example would present a reasonable approach to MIP chemosensor preparation. 

Control of colloid stability is used in a wide range of technological applications, for example [1] ... 

Interfacial chemistry and system hydrodynamics control the aggregation, deposition, and separation of particles and particle-reactive substances in natural aquatic environments and in many technological systems. Hydrodynamics (particle transport) are particularly sensitive to particle size and size distribution colloidal stability is usually determined by the presence of macromolecular natural organic substances. Recent theoretical and experimental studies of the effects of these two classes of variables on solid-liquid separation in aquatic systems are presented and discussed. 

In addition, hydrotrope solutions have been involved in reactions concerning solid particles. As examples may be mentioned the template-free synthesis of microtubules [34], important materials in nano-technology, and the more sophisticated role of hydrotropes to concurrently optimize the interfacial tension and the colloidal stabilization of rhodium particles in biphasic liquid-liquid alkene hydrogenation catalysis [35], Finally reaction kinetics has been used as a means to follow the association of hydrotrope molecules in aqueous solutions [36],... 

There are quite tangible differences in the performance of slow stabilization when wines have no protective colloids (cf. wine filtered on a membrane retaining any molecule with a molecular weight above 1000 Da). These effects ought to be even more spectacular in the case of rapid stabilization technologies. Indeed, the results presented in Figure 1.16 show the impact of prior preparation on the effectiveness of the contact process. 

DH Melik, HS Fogler. Fimdamentals of colloidal stability in quiescent media. In P Becher, ed. Encyclopedia of Emulsion Technology. Vol 3. New York Marcel Dekker, 1988, p 3. 

This comprehensive article, the third of a series, supplies a description of colloid fundamentals of emulsions and latexes. Information is included on their technical characteristics and their behaviour in technological processes, which are closely dependent on their colloid stability. The article provides the main colloid concepts useful in the technology and formulation of resin emulsions, polymer latexes and emulsion paints. 17 refs. ISRAEL... 

Depending on the application, a latex compoimd may contain up to nine compounding ingredients (7) deionized water, (2) antifoam, (3) colloidal stabilizers, (4) polymer stabilizers, (5) curatives, (6) tackifiers, (7) fillers, and (8) thickeners. All have specific functions that contribute to the outcome of the finished part (see Latex Technology). 

The interactions between surfactant solutions and solid surfaces play a key role in technologically important processes such as colloidal stabilization, ore flotation, and soil removal however, the interfacial aggregation of surfactant molecules is not yet well understood. 

At the times when DLVO theory was developed, the direct measurement of forces between colloidal particles and surfaces in solution was not possible, and the macroscopic observation of colloidal stability was the only experimental reference data. With increasing technological advancement, setups have been developed for the direct observation of such forces The surface force apparatus (SFA) allows for the measurements of forces between surfaces in solution [6], and with an atomic force microscope (AFM), forces on a colloidal particle can be detected [7]. It is a major success that DLVO theory predicts forces that agree nicely with the measured forces for large particle separations (more than 3-10 nm), but at the same time, it is obvious that in the regime of short particle separations, not aU effects are captured by DLVO. When the barrier for coagulation occurs at such low separations, the DLVO prediction for colloidal stability is not accurate (Fig. 2). 

Let us now address an interesting problem in colloid science and physical-chanical mechanics related to the contact interactions in disperse systems, namely, the possibility of spontaneous dispersion and the formation of thermodynamically stable colloid system. Originally, this problem was formulated by Max Volmer in 1927 [60,61] and later addressed by Rehbinder and Shchukin. Shchukin has made two principal contributions to the analysis of this problem [33,62-69]. The first is the detailed analysis of the conditions that make the process of spontaneous dispersion (at constant volume of the disperse phase, constant particle size, or constant number of particles) possible. Second, he proposed incorporating the entropy of mixing into the description of the conditions of spontaneous dispersion. The latter allows one to quantitatively estimate the concentration of the disperse phase in the disperse system formed. The analysis of the thermodynamics of spontaneous dispersion has important implications in the analysis of colloidal stability and in the control of various technological processes. 

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