Langmuir-Blodgett films noncentrosymmetric structures

Ashwell, G.J. (1999) Langmuir-blodgett films Molecular engineering of noncentrosymmetric structures for second order nonlinear optical applications. Journal of Materials Chemistry, 9, 1991-2003. 

Umemura, Y.. Yamagishi, A., Schoonheydt, R., Persoons, A., De Schryver, F. Langmuir-Blodgett films of a clay mineral and ruthenium(II) complexes with a noncentrosymmetric structure. J. Am. Chem. Soc. 124. 992-997 (2002)... 

In view of the potential technological importance of noncentrosymmetric organic crystals, several approaches have been evolved to artificially achieve noncentrosym-metry, which include electric field poling of polymers, self-assembly of molecular layers, Langmuir-Blodgett assembly of films and host-guest interaction in noncentrosymmetric hosts (Marder et al, 1994). Prediction and/or control of the three-dimensional structure of crystals, given only the information of molecular properties, however, remains difficult at present. 

When the appropriate chromophore is selected from an investigation on optical nonlinearity at the molecular level, the fabrication of this into a noncentrosymmetric structures is the next step. This is realized in the following forms single crystals, Langmuir-Blodgett (LB) films, and poled polymo-s. Since the main topic of this chapter is crystals, the latter two wiU be only briefly described later. Several methods to create noncentros5nnmetry in crystals have been investigated and these wiU be discussed in the next section. 

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