Particle Surface Modification

PARTICLE SURFACE MODIFICATION TO PRODUCE BIOLOGICAL LABELS 

There are several methods available for preparing surface functionalized metallic colloids for use as biological labels. The three most widely used fabrication methods include non-covalent absorption of biomolecules to the particle su face binding to the metal surface via a thiol functionalized cross linker, and covalent binding to a derivatized silica or polystyrene shell that encompasses the metal particle . 

Add30uLof 1% APTESto I mLofwater. Voitmi and add to gold colloid mixture. 

After 13 minutes add the diluted NaSilicate to the gold colloid solutitm. 

After 3-7 days, a thin (2-4 nm) silica shell will form. 

The surface properties of the particles can be modified according to the requirement. Surface modification of particles could be divided into three major categories according to the procedures employed. These are covalent modification, surface adsorption, and encapsulation. 

FIGURE 7.17 Polymer particles deforming under the pressure providing a cushioning effect. Polymer particles coated with colloidal silica particles (from Ref 101). 

Particle encapsulation is another technique that can be used for surface modification that involves the complete coating of a particle with polymer [104]. The net effective hardness in this case tends to be less than that of the core. Particle encapsulation in CMP, hence, could be used to reduce surface defects of the surface to be polished. It should be noted here that excessive coating of the particle could result in reduced abrasiveness and in problems with dispersion stability. 

Silane coupling agents have been used for many years to pretreat fibres for incorporation in composite materials to improve mechanical properties and resistance to aqueous environments and they are also effective in enhancing 

Organic titanates are thought to adsorb in a similar way. The coupling agents, may be added directly to the polymer-ceramic blend, blended directly 

A basic study of surface active species on the properties of filled systems was performed by Bigg( ) using coarse (5-44pm) steel spheres at volume fractions up to 0.7. This showed that addition of both a silane and a titanate coupling cigent increased the viscosity of polyethylene-steel composites. 

Coupling agents with unreactive paraffinic X groups have been shown to 

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In most practical uses of polymeric particles, their surfaces play a very important role by taking part in interfacial interactions such as recognition, adsorption, catalytic reactions, etc. When we want to use polymer particles, we first check whether the chemical and physical structures of the surfaces meet the purpose. If some of them do not satisfy the criteria, we may seek other particles or try to modify the existing particles. This chapter mainly deals with the modification of surface of existing particles. In addition to chemical modification of particle surfaces, modification of the morphology of particles is also described. 

The surface of polymer particles obtained by emulsion polymerization is occupied by emulsifier molecules, initiator fragments, and hydrophilic comonomer units. Therefore, desirable design of the surface ought to be done by choosing the emulsifier, initiator, and comonomer. Some of them are employed in aiming for postreaction at the surface to convert it into a functional one. When any change is necessary on the particle surface, modification of surface can be done by the following means ... 

In addition, ultraviolet light, infrared rays, corona discharge, and a plasma radiation halving method can also be carried out on particle surface modification. These methods do not need modifying agents, and are therefore beneficial for environmental protection. However, these technologies are complex and expensive. 

Particle surface modification could be characterized with the surface energy measurement, ilow the surface energy of dispersed particle affects the ER efiect was systematically addressed by Hao [95]. A set of oxidized polyacrylonitrile (OP) materials of different surface properties were employed for such a purpose. The five kinds of water-free ER fluids composed of oxidized polyacrylonitriles (OP) particle dispersed in a low viscosity silicone oil were used for correlating the ER effect with the particle surface energy. The powdered OP materials with average particle size 0.1-10 pm were treated at 150 C for 8 h, and then dispersed in silicone oil immediately at the particle volume fraction of 35 vol /o. The surface energy was measured by means of the dynamic wicking method [96]. Water and... 

Since most inorganic particles are not very compatible with polymers, mechanical agitation and ultrasonication are usually applied to facilitate particle dispersion. Particle surface modification and surfactants are also used to increase the compatibility between nanoparticles and the polymer matrix. Based on the original medium where the nanoparticles are dispersed, the manufacturing process for making polymer nanocomposites includes melt... 

This thin film technique can be used to better understand the mechanism of nanoparticle-polymer matrix interactions and to design particle surface modification for specific nanocomposite applications. Numerical analysis and finite element modeling of the nanoparticle embedding technique and the quantitative... 

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