Forces and Self-Assembly

B. W. Ninham and P. Lo Nostro, Molecular Forces and Self Assembly in Colloid, Nano Sciences and Biology, Cambridge University Press, Cambridge, 2010. 

On the basis of these observations, an interesting formation of nanostructures consisting of SWNTs was probably achieved by magnetic force, magnetic orientation, interaction of induced magnetic moment of SWNTs due to strong magnetic fields, and self-assembly of SWNTs due to hydrophobic interaction in aqueous solution and so on [46, 48]. 

Although the notion of monomolecular surface layers is of fundamental importance to all phases of surface science, surfactant monolayers at the aqueous surface are so unique as virtually to constitute a special state of matter. For the many types of amphipathic molecules that meet the simple requirements for monolayer formation it is possible, using quite simple but elegant techniques over a century old, to obtain quantitative information on intermolecular forces and, furthermore, to manipulate them at will. The special driving force for self-assembly of surfactant molecules as monolayers, micelles, vesicles, or cell membranes (Fendler, 1982) when brought into contact with water is the hydrophobic effect. 

An ordered antibody array has also been assembled on the solid surface by a combination of Langmuir Blodgett (LB) film method and self-assembling method. An ordered monolayer of protein A is deposited on the solid surface by LB method, which is followed by self-assembling of antibody. Individual antigen molecules which are complexed with the antibody array have been quantitated selectively by atomic force microscopy (AFM). 

Leikin, S., Rau, D. C., and Parsegian, V. A. (1994). Direct measurement of forces between self-assembled proteins. Temperature-dependent exponential forces between collagen triple-helices. Proc. Natl. Acad. Sci. 91, 276-280. 

This has led to a well-developed biochemistry, and has resulted in a much improved understanding of the properties of enzymes, natural photosynthesis, respiration, etc. These studies revealed that the structure of natural systems is controlled by intermolecular forces and the importance of organization and self-assembly was soon recognized. 

The present volume involves several alterations in the presentation of thermodynamic topics covered in the previous editions. Obviously, it is not a trivial exercise to present in a novel fashion any material that covers a period of more than 160 years. However, as best as I can determine the treatment of irreversible phenomena in Sections 1.13, 1.14, and 1.20 appears not to be widely known. Following much indecision, and with encouragement by the editors, I have dropped the various exercises requiring numerical evaluation of formulae developed in the text. After much thought I have also relegated the Caratheodory formulation of the Second Law of Thermodynamics (and a derivation of the Debye-Hiickel equation) as a separate chapter to the end of the book. This permitted me to concentrate on a simpler exposition that directly links entropy to the reversible transfer of heat. It also provides a neat parallelism with the First Law that directly connects energy to work performance in an adiabatic process. A more careful discussion of the basic mechanism that forces electrochemical phenomena has been provided. I have also added material on the effects of curved interfaces and self assembly, and presented a more systematic formulation of the basics of irreversible processes. A discussion of critical phenomena is now included as a separate chapter. Lastly, the treatment of binary solutions has been expanded to deal with asymmetric properties of such systems. 

The importance of SPM for the study of monolayers is that it allows the visualization of the structure and defects of transferred and self-assembled monolayers on solid substrates at length scales from <0.1 nm to > 10 pm. It is not fyet ) possible to image monolayers at liquid/fluid Interfaces with SPM techniques. However, it has already been shown that it is feasible to measure interaction forces between a colloidal particle and such interfaces in the presence and absence of monolayers ). 

To begin with it is best to place the field of nanolithography and its companion nanomanipulation in perspective. This is shown in Figure 21.2. Nanomanipulation, in principle, should also include manipulation using forces of self-assembly or other chemical forces and manipulations using optical tweezers. However, the word nanomanipulation is often used in a limited context where a SPM tip is used for manipulation of a nano-object. We stick to this definition, partly to reduce the scope of the review and partly because other manipulations are not in the area of expertise of the author. 

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