Surface modification procedure

CdS sols with fluorescence quantum yields close to 100% are obtained by certain surface modification procedures For example, dilution of an aqueous sol with... 

The methoxylation can be carried out by reacting silica with methanol vapor at 300-400°C, or by refluxing silica in methanol (21,36). Because the infrared spectrum of the modified surface is well understood (36) we chose to use this system as a model to test the feasibility of using Raman spectroscopy (21 ) for studying such surface modification procedures. 

A practical problem is that the sputtered chemical complexes often exhibit only a transitory existence. Traditional mass spectrometric techniques provide information on gross removal but little understanding of the mechanism involved. Data requirements in this area include gross removal rates, nature of ejected species, and changes to surface stoichiometry. In Sect. 6.5.1., the influence of surface chemistry on the nature of the sputtered species, and in particular on secondary ion fractions will be discussed. The role of surface chemistry and surface modification procedures on impurity control will be elucidated there. 

A detailed study of the problem is called for to permit the design of surface modification procedures capable of meeting desired degrees of performance modification. 

FIGURE 3.63 Schematic representation of multistep surface modification procedures for polymeric materials that comprise a low-pressure plasma treatment either for activation/functionalization (a, b, and d) or cross-linking (c). Source Nitschke et al. [90]. Reproduced with permission from John Wiley Sons. 

To achieve enhanced cell adhesion and proliferation in vitro which probably leads to a better integration of the prosthesis into the surrounding tissue the cell adhesion mediator fibronectin was coupled to the surface of silicone. Figure 40 shows the two principal steps of the appHed surface modification procedure. Argon plasma treatment and subsequent exposure to air of the silicone samples leads to the formation of hydroperoxide groups on its surface which are used to initiate polymerization of acrylic acid (AAc), methacrylic acid (MAAc) and gly-cidyl methacrylate (GMA) generating carboxylic and epoxy groups, respectively. 

The low diffusion coefficients of large proteins is a major problem. This can be overcome by increasing the pore size to values above 100 nm. However, large pores reduce the accessible surface area and so decrease binding capacity. A more attractive solution is the application of polymeric surface modification procedures, which will be described later [36]. 

In specific cases where cell attachment is necessary to ensure proliferation, plasma-modified in vitro cell containers show dramatic improvement over untreated containers. By using surface modification procedures, the performance of PE can be substantially improved compared to the untreated state. 

Surface pretreatment is a crucial step whieh determines the surface activity for the subsequent graft polymerization. Most inorganic oxide surface modification procedures rely on surface silylation whereby silane compounds with the desired functionality are reacted with siuface hydroxyls. For example, the surface of amorphous silicas consists of silanol (< [ ]>) and/or siloxane (< [ ]>) groups, with reported hydroxyl concentration, on a hydroxylated amorphous silica, of 4.6 hydrox-yls/nm [53]. 

The final part of the surface modification procedure is monomer grafting via free-radical polymerization. Schematic illustrations of the graft polymerization of vinylpyrrolidone (VP) and vinyl acetate (VAc) on to silica are shown in Figs 2a and 2b, respectively. In both cases, an initiator is used to initiate the grafting reaction by creating free radicals that initiate polymer chain growth. 

Two novel surface modification procedures, increasing the alloy Al reservoir and gas annealing (2 h in Ar -i- 4% H2 -1- 2% H2O at 1100-1200°C) have been developed by the CEC funded SMILER project with the objective of extending the lifetime of relevant EeCrAlRE alloy components across the industrial operating temperature range. 

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