Metal colloids devices

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. 

Whether there is currently a nanotechnology is a question of definition. If one asks whether there are (or are soon likely to be) commercial electronic fluidic, photonic, or mechanical devices with critical lateral dimensions less than 20 nm, the answer is no, although there may be in 10 to 20 years. There is, however, a range of important technologies—especially involving colloids, emulsions, polymers, ceramic and semiconductor particles, and metallic alloys—that currently exist. But there is no question that the field of nanoscience already exists. 

Analytical-operational Difficulties. In order to work close to the conditions in natural waters, very low concentrations of metal ions (in the nanomolar range) and of particles as well as pH values in the neutral range have to be used. Analytical difficulties occur because of undesired adsorption of metal ions to the experimental devices (walls of beakers, glass filtration devices, etc.) and of insufficient separation of the particulate and dissolved phase (particles in the colloidal size range). 

Up to now, a large part of the international scientific attention was devoted to the study of metallic nanoparticles (either single particles or in a colloid ensemble) (3, 14). Milling nanometric apertures in a metallic film is an intuitive way to manufacture new nanophotonics devices that are robust and highly reproducible. Although this concept appears very simple, such apertures exhibit attractive physical properties, such as localization of excitation light, strong isolation fi om emission produced by unbound species, and an increase in apparent absorption and emission yield. The simplicity of the structures and their ease of use should further expand their application towards the real-time detection and identification of a small number of molecules. 

Silicate mortars, however, will not be injured by storage in warm locations, with the possible exception of a few with limited shelf life, where it is possible that shelf life may be shortened. But if the liquid component (sodium or potassium silicate) is frozen, the fluid mixture (a colloid) will "break" and the silicate will come out of solution and coat itself on the inside of the metal containers. If this happens, the mortar will not function until the silicate is redissolved— mixed back with solutions using a power-stirring device such as a "Lightning Mixer."... 

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