Colloidal Techniques

As a POC (point of care) device semi-quantitative flow-immunoassay methods for the detection of antibodies or antigens had been developed and are well establish in e.g. pregnancy tests. This format is also known as strip test, one step strip test, immunochromatographic test, rapid flow diagnostic, rapid immunoassay or lateral flow immunoassay (LFI). The label is anyway a colored colloidal particle. Additionally to metal colloids, carbon (black) and silica or latex (various colors) are in use. 

First devices developed in the early 80s had been built on paper strips developed with an appropriate gold reagent in a plastic tube in the presence of urine or serum [16,17]. The analyte-reagent mixture migrates up the strips towards the top end. A purple dot or band develops which indicates the presence of the corresponding antigen in 5 minutes or less. 

Strip tests are simple, rapid and cost efficient. A disadvantage is the limited sensitivity of the assay and lack of multidimensional multi-analyte capabilities. Recently, micro -fluidic cluster chromatography devices proved to be promising candidates to overcome these limitations. 

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The approaches used for preparation of inorganic nanomaterials can be divided into two broad categories solution-phase colloidal synthesis and gas-phase synthesis. Metal and semiconductor nanoparticles are usually synthesized via solution-phase colloidal techniques,4,913 whereas high-temperature gas-phase processes like chemical vapor deposition (CVD), pulsed laser deposition (PLD), and vapor transfer are widely used for synthesis of high-quality semiconductor nanowires and carbon nanotubes.6,7 Such division reflects only the current research bias, as promising routes to metallic nanoparticles are also available based on vapor condensation14 and colloidal syntheses of high-quality semiconductor nanowires.15... 

In the colloidal technique, the size and distribution of a dispersed thoria (Th02) phase is controlled to produce dispersion-strengthened alloys, primarily with nickel as the metallic phase. The so-called TD (thoria-dispersed) nickel has modest strength at room temperature, but retains this strength nearly to its melting point. TD nickel is 3 to 4 times stronger than pure nickel in the 870-1315°C range, and oxidation resistance of the alloy is better than that of nickel at 1100°C. 

Colloidal techniques, for molecuarlar precursor transformation to materials, 12, 47 Colloids, overview, 12, 71—99... 

To realise this, first very homogeneous OC-AI2O3 supports were prepared by using colloidal techniques. Colloidal filtration was used for the preparation of flat supports, while a centrifugal casting technique was developed to prepare highly smooth and round tubular supports. 

In summary, micro-electrophoresis Is a powerful and basic colloidal technique but In order to obtain reliable results a number of precautions have to be taken J. 

The oil extracted from a well usually contains water dispersed as a fine emulsion. The de-emulsification of the oil is an important part of the overall processing, and improved and more economical methods of achieving this depend on the application of colloid techniques. 

The development of sol-gel science and related colloidal techniques is contributing significantly to the development of the advanced materials required by the high technologies. For example, a crucial issue in the manufac-mre of ceramics for electronics is reliabihty. Improved... 

Historically, QDs were first synthesized in glass matrices where the slow difiusion of precursors provided some measure of size control. In the last couple of decades, colloidal techniques have advanced to the point that parameters such as precursor reactivity, temperature, surfactants etc. can be independently tuned to control and regulate nanocrystal formation. This enables the synthesis of high quality solvent dispersible particles that may be further processed using simple wet-chemical methods. Qne of the earliest techniques employed to achieve this is known as the arrested precipitation method where the semiconductor growth is arrested after the... 

Malghan, S.G., D.B. Minor, P.S. Wang, and C.P. Ostertag. 1990. Coating of fibers by colloidal techniques in ceramic composites. Ceramic... 

Micro Structured metals have recently been coated by the sol-gel technique to obtain a Cu-Zn-Al catalyst system or by the emulsion colloid technique, which is similar to a standard washcoating procedure, to obtain a PdZn/ZnO catalyst system... 

Fabrication of tensile test bars by colloidal techniques -injection molding and colloidal consolidation. 

In principle, many chemical approaches exist for the preparation of quantum dot clusters. Qassical preparative methods include wet colloidal techniques, growth in dielectric glass matrices, and growth in polymers. In these materials, however, cluster or particle sizes are usually nonuniform, and agglomeration of... 

The colloidal techniques described in Chapter 4 provide considerable benefits for the control of the packing uniformity of the green body. The production of green bodies with uniform microstructure from a fully stabilized colloidal suspension of spherical, fine, monodisperse particles has not been incorporated into industrial applications where mass production is desired and fabrication cost is a serious consideration. Colloidal techniques, however, play an important role in the low-cost forming methods of slip casting and tape casting, as well as in the less commonly used methods of eletrophoretic deposition and gel casting. 

V. Agarwal, P. Chahal, R. R. Tummala, and M. G. Allen, Improvements and Recent Advances in Nanocomposite Capacitors Using a Colloidal Technique , Proceeding of 1998 Electronic Components and Technology Conference, (1998), pp. 165-170. 

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