Applications phosphonate thin films

In certain cases, self-assembly methods can be employed to prepare multilayered thin films analogous to LB films. Typically, once the surface has been primed with a molecular adhesion layer, subsequent layers are assembled in a layer-by-layer fashion where the end group of the previously deposited layer directs the assembly of the next layer. Strong electrostatic or covalent interactions between the layers serve to stabilize the assemblies. The most notable examples of self-assembled multilayered films are those based upon metal phosphonates [21]. Although these multilayers are structurally analogous to LB films, their thermal and solvent stability makes them potentially more useful in many applications, including electron-transfer studies. 

Regarding applications, long-chain phosphoric (and also phosphonic) acid esters are expected to have potential for applications in areas where the specific surface functionalization of oxides by extremely thin films is essential to the quality of a product. One area where application of octadecyl phosphate on tantalum oxide has already proven to be successftd is optical biosensor technology, where the use of well-controlled ODP self-assembled monolayers on optical waveguide chips has been demonstrated to increase both the specificity and selectivity when sensing extremely low quantities of biomolecules using evanescent field and fluorescence techniques. The application potential will be further increased if a second functionality can be introduced in the terminal, phosphoric acid esters. 

FIGURE 16 Molecular thin films of phosphonates bearing noncentrosymmetric chromo-phores for NLO applications. 

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