Adsorbed coatings

The results of work [ 135] are of specific interest. The work surveyed the influence of the nature and structure of adsorbed layers upon the mechanism of deactivation of He(2 S) atoms. It has been shown that on a surface of pure Ni(lll) coated with absorbed bridge-positioned molecules of CO or NO, the deactivation of metastable atoms proceeds by the mechanism of resonance ionization with subsequent Auger-neutralization. With large adsorbent coverages, when the adsorbed molecules are in a position normal to the surface, deactivation proceeds by the one-electron Auger-mechanism. The adsorbed layers of C2H4 and H2O on Ni(lll) de-excite atoms of He(2 S) by the two-electron mechanism solely. In case of NH3 adsorption, both mechanisms of deactivation are simultaneously realized. Based on the given data, the authors infer that the nature of metastable atoms deactivation on an adsorbate coated metal surface is determined by the distance the electron density of adsorbate valance electrons is removed from the metal lattice. 

Human serum albumin (HSA) may be used as a protectant against adsorptive loss of proteins present at low concentrations. HSA is present at higher concentration than the active substance and is preferentially adsorbed, coating the surface of interest and preventing adsorption of the drug. For example, insulin is subject to adsorptive loss to hydrophobic materials. Addition of 0.1-1.0% HSA has been reported to prevent this adsorptive loss [9],... 

Hemstreet, R.A. (1957) Adsorbent-coated thermal panels. US Patent 3,338,034. 

The colloidal particles are often deposited on metallic electrodes in the form of adsorbed coatings. Rubber and graphite coatings can be formed in this way, using solvent mixtures (water-acetone) as the dispersion media. The advantage of this method is that additives can firmly be codeposited with, for example, rubber latex. Thermionic emitters for radio valves are produced in a similar manner. The colloidal suspensions of alkaline earth carbonates are deposited electrophoretically on the electrode and are later converted to oxides by using an ignition process. 

Alternatively, air drawn through Florisil or silica gel adsorbent coated with acidified 2,4-dinitrophenylhydrazine (DNPH) the DNPH derivative of formaldehyde desorbed with isooctane, and solvent exchanged to methanol or acetonitrile the solution analyzed by reverse phase HPLC (U.S. EPA Method TO-11,1988) recommended air flow rate 500 mL/min sample volume 100 L. 

Beider et al. [90] described poly (vinyl alcohol) coated microfluidic devices in NCE for a suppressed electroosmotic flow and improved separation performance of labeled amines. A threefold increase in separation efficiencies was obtained on coated chips. In PVA-coated channels, rinsing or etching steps could be omitted, which are necessary for uncoated devices. Wu et al. [100] described multilayer poly(vinyl alcohol)-adsorbed coating on... 

Four coatings, such as PEG (8.5% w/v), PVP (2.5% w/v), HEC, and EPDMA, were evaluated for PCR on glass chips. It was found that the amount of PCR products were 13%, 78%, 0%, and 72%, respectively, when it was 100% using a conventional PP tube. These values were also compared to 50-120% when only silanization was used for passivation. While the first three are dynamic coatings, the last one is an adsorbed coating [935]. 

With lack of specificity and low sensitivity established as two major drawbacks of uncoated surfaces, it is clear that an important key to the performance of adsorption-based AW chemical sensors is the adsorbent coating material. All... 

Zhao, Q., Zhu, Q., Shin, W.Y., Shin, W.H. (2006). Array adsorbent-coated lead zirconate titanate (PZT)/stainless steel cantilevers for dimethymethylphosphonate (DMMP) detection. 

Solid-phase microextraction, first reported by Belardi and Pawliszyn in 1989, is an alternative sampling technique. The method has the advantages of convenience and simplicity, and it does not release environmentally polluting organic solvents into the atmosphere. The method is based on the extraction of analytes directly from liquid samples or from headspace of the samples onto a polymer- or adsorbent-coated fused silica fiber. After equilibration, the fiber is then removed and injected onto the gas chromatograph. ... 

Adsorbents Adsorbents coat the GI tract, adsorbing the bacteria or toxins that cause diarrhea. Commonly used adsorbents are ... 

Supelco (Chromatographic Products for Analysis Purification Catalogue, ) supply a variety of solvent desorption tubes , which are cartridges that remove specific impurities (e.g. LpDNPH cartridges which contain a high purity silica adsorbent coated with... 

As one can see, the effective tunnel barrier height decreases with increasing number of intermediate states n and so depends on the oxide or adsorbate coating (Fig.3). 

Adsorbents coat the wall of the GI tract and adsorb bacteria or toxins that are causing the diarrhea. Adsorbents include kaolin and pectin, which are combined in the over-the-counter drug Kaopectate, and other antidianheals. Pepto-Bismol is considered an adsorbent because it adsorbs bacterial toxins. Bismuth salts can also be used for gastric discomfort. Colestipol and cholestyramine (Questran) are prescription drags that have been used to treat diarriiea. 

In general, adsorbed coatings work well for applications requiring reduced EOF. Furthermore, they are attractive because a wide variety of chemistries exist and their deposition is very simple. On the negative side, however, adsorbed coatings have a finite lifetime requiring recoating more frequently than covalent systems. 

---