Chemical modification of surfaces

Broadening of the optimal pH range for reactive dye biosorption by chemical modification of surface functional groups of Corynebacterium glutamicum biomass... 

The reader may notice many cross-references between the five contributions, which support the view that chemical modification of surfaces, particularly the nanostructuring, is not only interesting for its own sake, but also relevant to a wide range of practice applications. Their seminal role in bioelectrochemistry, bio-sensing, electrocatalysis and electroanalysis among others is clearly evident in this volume. 

Chemical modification of surface residues of HRP is one method which may offer some improvement in thermal or long-term stability of the enzyme. The -amino groups of the six surface Lys residues can be modified by reaction with carboxylic anhydrides and picryl sulfonic acid (296). In this example the number of sites modified was found to be more significant than the chemical nature of the modification, at least as a criterion for improved stability. Other methods explored include the use of bifunctional crosslinking reagents to couple surface sites on the enzyme (297). Future developments are likely to be concerned with the selection of site-directed mutants of HRP C that show enhanced thermal stability. Dramatic increases in thermal stability of up to 190-fold have been reported recently for mutants of Coprinus cinereus peroxidase (CIP) generated using a directed evolution approach (298). 

Chemical Modifications of Surface Functional Groups with Elements Having High Photoelectric Cross Sections... 

The examples of chemical modification of surface diamagnetic sites are presented in Section 9 (see Tables 7.11 and 7.12). Another method is based on the two-step modification of SC. The diamagnetic sites (=Si-0)2Si are efficient acceptors of low-molecular free radicals (see subsection 9.2) ... 

Thus, the experimental results presented in this section indicate that the chemical modification of surface defects is a convenient and efficient method for the preparation of reactive intermediates with different structures. Using this method, one can synthesize various groups and obtain the data on their spectral parameters and reactivity, pathways and rate constants of thermal, chemical, and photochemical processes involving these groups. 

Major concerns are the availability and limitations of the analytical techniques necessary to determine that surface modification has occurred, and the extent to which it has occurred. Herein, the state-of-the-art of the chemical modification of surfaces is presented by 17 chapters that also discuss the nature of the binding of the pendant groups to the surface and their frequency and spatial distributions. The principal focus in these chapters is on modification of materials for catalytic purposes and the modification of organic and inorganic electrode materials for electrocata-lytic and photoelectrochemical applications. 

The development of methods of producing chemical compounds on silica surface (chemical modification of surface) is essential for the creation of new highly specific adsorbents, selective heterogeneous catalysts, active fillers of polymeric materials, effective thickeners of dispersive media. Of prime importance for many practical applications of modified silicas is hydrolytic and chemical stability of surface chemical compounds. For example, the chemical compounds formed upon the interaction between silanol groups and alcohols by the reaction ... 

The widest application for the synthesis of silicas with attached sSiH groups is enjoyed by methods of chemical modification of surface with various silanes. 

In most cases in order to carry out chemical modification of surface it is advantageous to use vapours of suitable olefinorganosilanes or their solutions in organic solvents. When the surface treatment involves the application of aqueous solutions of vinyltriethoxysilane, for example, the deposited coatings often have non-reproducible properties which is due to the difficulties in controlling polymerization of the formed vinylsilanetriol [89,100,102-106]. In conformity to the data of Refs.[107,108] the application of vinyltrichlorosilane for chemical modification of silica provides higher contents of attached olefin groups than the treatment of hydrated surface with vinyltriethoxysilane. 

To our mind, a similar scheme can be applied for chemical modification of surface as follows. In the first stage organosilicon modifiers with bulky substitutes such as triphenyl, triisopropyl etc. should be used. In the second stage the sample is modified with a proper modifier penetrating the original surface of a support through the gaps. 

The chemical modification of surfaces and films i essential in the manufacture of integrated circuits. Patterns and material must be transferred to substrate surfaces and removed from them. As the dimensions of advanced electronic devices shrink to the submicron and molecular scale, properties of the processing techniques become increasingly critical. Characteristics such as low temperatures, low levels of induced dam. ge and contamination, and molecular scale selectivity and controllabilit] are essential. The use of radiation-induced chemistry is desirable if it can be conducted at lower temperatures and with smaller levels of damage and contamination than particle impact and thermal methods. 

Sebastian, I Istvan, H Process for the chemical modification of surfaces of inorganic so-hds. US3956179, 1976 GB1460315, 1975 DE2313073, 1973. 

Chemical modification of surface silanol groups on the glass surface affects both the spreading of liquid films [97] and the residual adsorptive properties of glass capillary columns. Thus, the surface wettability problems can largely be solved through different individual surface treatment techniques, or their combination. Most of the recent developments in this area have been reviewed [100]. 

J.E. Crowell. Chemical Modification of Surfaces The Effect of Potassium on the Chemisorption of Molecules on Transition Metal Crystal Surfaces. Ph.D. thesis. University of California, Berkeley, 1984. 

Over the years, various advanced techniques for localized material removal, deposition or chemical modification of surface in the nanoscale with the help of STM tip have been developed. STM and AFM are the potential tools in the fabrication of nanostructure in an atomic resolution. However, in AFM the... 

It is evident from this brief overview of adhesion technology, nature, and science that many different specialists have an interest in the definition of what adhesion is, in the observing and measurement of the adhesive forces, in the chemical modification of surfaces to control adhesiveness, in improving adhesion so that aircraft do not fall apart, and in reducing adhesion so that cars do not seize up. In other words, adhesion is an interdisciplinary subject. Indeed, it connects many different subjects because of its common function and value. 

B. E. Koel, R. G. Nindhaum "Chemical Modification of Surface Properties" Proceedings, Ind. Univ. Advanced Materials Conference, Denver (Ed J. G. Morse), 1987... 

Many factors such as adhesion between components, fiber topography, and kinetic parameters of crystallization of semicrystalline matrix have been reported to influence transciystallinity. The transcrystallinity phenomenon in the natural fibers/polypropylene system is affected by the different type of chemical treatment of lignocellulosic materials. Moreover, the ability of natural filler to induce nucleation in polypropylene matrix is also dependent on the kind of chemical modification of surface fibers. Predominant nucleation ability was found for unmodified fibers. However, chemical modification of fiber surface slightly depressed the nucleation of polypropylene matrixes. 

The above cases dealt with polymers that were chemically modified in solution. Chemical modification of surfaces of solid polymers is an attractive alternative technique. Oxidation of polystyrene surfaces has b rigShown to increase the negative charging capacity linearly.Introduction of carbonyl coo taining functionalities (acceptor groups) is known to occur. Oxidation and ozonization of branched (unsaturated) polyethylene surfaces led to ver. similar results, i.e., enhanced negative charging- capacity.Oxidation of coal was similar in effect. ... 

For the subsequent photo-chemical modification of surface chemistry, samples were immersed in 1,5-hexadiene, diallylphthalate (DAP), or perfluoro(4-methylpent-2-ene) (PFMP), dried and irradiated. A monochromatic (excimer) lamp emitting at 222 nm was employed and the irradiation performed for 5 or 10 min in an inert atmosphere. Samples were irradiated on both faces in all cases. In general, the samples were extracted for 4 hours in water/methanol and further 4 hours in petroleum ether before the treatments and washed after the photo-chemical modification in order to remove uncrosslinked residuals. 

Figure 9. The effect of chemical modification of surfaces on the electrode linearity.

In this chapter we wish to explore not only the influence of micelles on reaction rates and the course of reactions, both chemical and photochemical, but also the stability of surfactants themselves and how aggregation can affect their stability. The chemical modification of surface-active agents and attempts to polymerize surfactant micelles will also be covered. The literature on reactivity in micellar systems has grown enormously since 1968 when an account of the pharmaceutical aspects was given in the first edition of this book [1], to the extent that a book has been devoted to the subject reviewing and collating the data in the literature prior to mid-1974 [2]. Here we can probably only hope to extract some of the salient features of the subject, and could certainly not claim to be comprehensive. The reference list, however, contains several reviews which should be consulted for more detailed treatments. The analytical consequences of solubilization of chromophoric species and change in the apparent dissociation constants of compounds in the presence of surfactants is also discussed at the end of the chapter. 

---