GROWTH OF ORIENTED MOLECULAR-SIEVE CRYSTALS ON ORGANOPHOSPHONATE FILMS

THE successful construction Of complex organic/inorganic biomimetic systems(1-3) has demonstrated the great power of supramolecular pre-organization and templating in controlling crystal growth(4). For instance, polar organic surfaces or surface-attached polar groups can induce the formation of thin films of iron oxide(5). It would be of great interest, for the design of novel devices such as sensors or catalyst membranes(6), to be able to control the growth on surfaces of porous crystals with oriented channels: such channels could, for example, control the access of molecules to the surface of a field-effect transistor in a sensor device. Films and membranes with non-oriented channels have been prepared by depositing or growing zeolite(7-12) crystals on metal or metal-oxide supports(13-21); in one case(21), pre-grown crystals of an aluminophosphate zeolite were oriented by application of an electric field. Here we report the oriented growth of crystals of a zinco-phosphate zeolite on gold surfaces modified with metal phosphonate multilayer films. We attribute the high degree of orientation (>90%) to a strong affinity between the phosphonic acid groups of the phosphate multilayer and the (111) faces of the growing crystals.