Uncoated particles

CA 45, 2670.(1951) (Completeness of coating of HE s grains with wax can be detd by examining them under UV radiation. The uncoated particles are purple colored whereas the coated material has a yel-white or a blue-white fluorescence) 9)A.LeRoux, MP 33,... 

Calvo, VilaJato, and Alonso studied chitosan-and poly-L-Lysine (PLL)-coated poly-e-Caprolactone (PECL) nanocapsules for ocular application. In comparison with commercial eyedrops, the systems investigated (uncoated, PLL-coated, and chitosan-coated nanocapsules) significantly increased the concentrations of indomethacin in the cornea and aqueous humor of rabbit eyes. The chitosan-coated formulation doubled the ocular bioavailability of indomethacin over the uncoated particles, whereas the PLL coating was ineffective. The authors concluded that the specific nature of chitosan was responsible for the enhanced indomethacin uptake and not the positive surface charge. Both the PLL- and chitosan-coated nanocapsules displayed good ocular tolerance. ... 

The column is perhaps the most important feature of a GC system. It contains the stationary phase and thus effects the separation of components in a mixture. The column may be made of glass or metal and typically 2-6 mm i.d. and 1-3 m in length when packed with stationary phase material or 0.2-0.7mm i.d. and lO-lOOm long if in the form of a capillary column. Columns are formed into a coil of between 4 and Sin (10-20cm) in diameter and specially designed end fittings are used to connect the columns to the injector and detector with minimum dead volumes. A packed column contains solid particles of uniform size coated with stationary phase in GLC or uses uncoated particles as the stationary phase in GSC (Figure 5.4). 

While effective removal of surfactant molecules from freshly precipitated nanoparticles constitutes one of the involved issues in microemulsion synthesis, a coating of surfactants on nanoparticles has been found to improve their luminescence behavior in certain cases. Thus, Fei etaL [284] synthesized a-Fe203 particles from reverse microemulsions in which sodium dodecyl benze sulfonate (DBS) was the selected surfactant. The a-Fe203 organosols with the particles coated by DBS and heat-treated at 140 C showed strong visible luminescence while the uncoated particles prepared under similar conditions were not luminescent. 

Nation wt.% Radius of Uncoated Particle r, (nm) Radius of Coated Particle r (nm) Thickness of Nation Coating r -r, (nm)... 

FIGURE 10.2 TEM images of (a) sodium stearate-coated Cu nanoparticles and (b) uncoated particles. 

The term steric stabilization was used first by Heller and Pugh [34] in situations where uncharged particles were prevented from flocculating by adsorption of non-ionic polymeric molecules. We have discussed enthalpic and entropic components of steric stabilization in Chapter 8. The free energy of interaction of two spherical lyophobic particles of radius a coated with an adsorbed layer of thickness 8 and surface layer concentration c, at a distance Hq between the surfaces of the uncoated particle is given by... 

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