The microstructure has a great influence on the macro-properties of polycrystalline molecular sieve films, such as the molecular sieve mechanism dependent separation of multi-component substances, the host-guest interaction dependent response of probing molecules, and the composite functions depending on the self-assembly within the channels. Accordingly, the controlling of orientations and the depressing of twin-crystal formation present a great challenge in the area of molecular sieve preparation.

In their published Communication, the authors have reported a new Langmuir-Blodgett approach for the coating of crystal seeds.

By employing the highly ordered and micro-size MFI molecular sieve as the building block, and by utilizing a "green" aqueous soft carrier, they were able to prepare highly ordered mono-layer crystal seeds. Then, by controlling the kinetic factors of the molecular sieve precursor, they could realize the controlling of the anisotropic growing rates of secondary growing processes, and could effectively depress the occurring of crystalline twin-planes. Consequently, highly ordered and low crystal density ultra-thin MFI molecular sieve films without twin-crystals were prepared. Selective electrodes prepared by means of this new method exhibited precise molecular dimension recognition functions.

The research results were published as a Communication in the newly issued Journal of American Chemical Society (J. Am. Chem. Soc., 132 (2010) 1768-1769).

SEM images of the substrates, the oriented seed monolayer, and the b-oriented membrane(Picture provided by DICP)