Self-assembled monolayer (SAMS) are commonly produced by immersing substrates in organic solutions containing trichlorosikme coupling agents. Unfortunately, such deposition solutions can also form alternate structures including inverse micelles and lamellar phases. The formation of alternate phases is one reason for the sensitivity of SAM depositions to factors such as the water content of the deposition solvent. If such phases are present, the performance of thin films used for applications such as minimization of friction and stiction in rnicromachines can be seriously compromised.Jnverse micelle formation has been studied in detail for depositions involving lH-, lH-,

The effects of algae concentration, ferric chloride dose, and pH on the flocculation efficiency of the freshwater algae Chlorella zofingiensis can be understood by considering the nature of the electrostatic charges on the algae and precipitate surfaces. Two critical conditions are identified which, when met, result in flocculation efficiencies in excess of 90% for freshwater algae. First, a minimum concentration of ferric chloride is required to overcome the electrostatic stabilization of the algae and promote bridging of algae cells by hydroxide precipitates. At low algae concentrations, the minimum amount of ferric chloride required increases linearly with algae concentration, characteristic of flocculation primarily through electrostatic bridging by hydroxide precipitates. At higher algae concentrations, the minimum required concentration of ferric chloride for flocculation is independent of algae concentration, suggesting a change in the primary flocculation mechanism from bridging to sweep flocculation. Second, the algae must have a negative surface charge. Experiments and surface complexation modeling show that the surface charge of C. zofingiensis is negative above a pH of 4.0 ± 0.3 which agrees well with the minimum pH required for effective flocculation. These critical flocculation criteria can be extended to other freshwater algae to design effective flocculation systems.

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Eight crown ethers with pendent carboxylic acid groups are immobilized on silica gel and utilized for column concentration of alkali metal cations from dilute aqueous solutions. The column concentration selectivity and efficiency are found to be strongly influenced by (1) the cavity size of the crown ether unit, (2) conformational positioning of the proton-ionizable side arm with respect to the crown ether cavity, and (3) capping of residual silanol surface groups with trimethylsilyl functions. By use of a chromatographic stripping technique, selective column concentration of Na(+), K(+), (Rb(+) and Cs(+)), and Cs(+) by different functionalized silica gels has been achieved.

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In the fabrication of MEMS devices, what has come to be known as "release stiction" occurs when the device is removed from the liquid phase into the ambient air. One widely used method for dealing with stiction is to deposit a hydrophobic coating on the surface of the device before it is removed from the liquid phase. This method can produce coatings with inconsistent morphology and device yield. This is to be compared with a new coating deposition scheme developed at Sandia National Labs, termed VSAMS (vapor-deposited self-assembled monolayers) that employs supercritical CO 2 drying and chemical vapor deposition to address many of the concerns associated with release stiction. VSAMS is attractive due to its process benefits, which include increased throughput, reduced waste, and most importantly, it can be easily scaled to full wafer production. It is also attractive because films produced by this method are uniform and very hydrophobic. The deposition step makes use of a class of compound that is particularly suited for vapor phase reactions, amino-functionalized silanes. The yield of microengine test devices coated with films made from amino-functionalized silanes was examined over an extended period. Their function was determined before and after the application of VSAMS. The advantage of using amino-functionalized silane precursors for VSAMS is related to the strength of the bond between the film and the polysilicon surface as evidenced by the fact that films made with these precursors are stable across the entire humidity scale.

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