Ultrathin films fabricated by Langmuir-Blodgett (LB) technique is a powerful tool in creating carefully controlled supramolecular structures of organized molecular assemblies, which have their potential applications in optical, electrical and numerous other fields. The bulk properties of the materials incorporated into Langmuir-Blodgett (LB) films can be controlled by the organization of molecules in the films and also by changing various LB parameters. Thin films with carefully designed structures and properties have attracted a great deal of interest in recent years [1] due to their potential applications in a number of different fields, such as sensors [2], detectors [1], surface coating [1], optical signal processing [3], digital optical switching devices [4], molecular electronic devices [5], nonlinear optics and models mimicking biological membranes [6]. These applications require, in general, well ordered films consisting of molecules with specific properties, carefully aligned with respect to each other and the substrates possessing high degree of stability to thermal and chemical changes. The possibility to synthesize organic molecules almost without limitations and with desired structure and functionality in conjunction with Langmuir-Blodgett (LB) film deposition technique enables the production of electrically, optically and biologically active components on a nanometer scale. It is extremely important to get an idea about the relation between the ultrastructure as well as also the domain structure and various physical properties of such system. The basic physics involved in such characterizations is a topic of fundamental importance. The structure, morphology, configuration and various other physical properties of the films obtained by Langmuir-Blodgett (LB) technique can be easily modified, that may suit for any specific application.
Photophysical characterizations of these films are extremely important in order to get an idea about the molecular mechanism involving in their formation and to study the structure and conformation at the molecular level as well as also to probe the molecular organization. Spectroscopy is one of the most celebrated versatile and useful analytical tool to investigate the photophysical and photochemical processes involved the molecule, in its ground state as well as also in the excited states. Molecular organization, nature, rigidity and shape of the molecule as well as the environment play important role in determining the various photophysical properties of the molecules. Moreover in some cases the optical and electrical characteristics of molecules are changed markedly when they are incorporated into some inert matrices of restricted geometries such as silica gel, glass, zeolites, polymer matrices, micelles, lipid bilayers and Langmuir-Blodgett (LB) films. These are manifested in the marked changes in electronic spectra, as well as in the relaxation processes from the excited state of the molecules. Detailed photophysical investigations of these films are necessary from the point of view of their various technical applications.
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