Facile Monolayer Assembly of Fluorophore‐Containing Zeolite Rods in Uniform Orientations for Anisotropic Photoluminescence

Abstract

Which way to turn: The tendency of microcrystals to attach to surfaces through their largest faces has resulted in two orientations of zeolite L monolayers on glass. Fluorophore‐containing cylindrical and hexagonal columnar zeolite L crystals assemble into vertically and horizontally oriented monolayers, respectively, on glass plates (see pictures). The photoluminescences of the monolayers are highly anisotropic.

Effective manipulation of the microstructure of zeolite film by hydrothermal pretreatment

“…Taking Mordenite Framework Inverted (MFI) zeolite [1] (symmetry: orthorhombic; space group: P nma ; unit cell constants: a = 20.1 Ǻ , b = 19.9 Ǻ , and c = 13.4 Ǻ ) as an example, the pore system consists of straight channels (pore size: 0.53 9 0.56 nm) interconnected by zigzag channels (0.51 9 0.55 nm) [2]. In addition to their traditional uses as catalysts, adsorbents and ionic exchangers [3], zeolites can also be fabricated into thin films and used as separation membranes [4][5][6][7][8], selective sensors [9,10], low-k materials [11,12], corrosion-resistant coatings [13], and optical materials [14,15]. In the synthesis of high-quality zeolite films, the accurate manipulation and optimization of their microstructures, such as crystallographic preferred orientation (CPO), thickness, intergrowth and grain boundary structures, is critical.…”

“…Compared to randomly oriented membranes, the b-oriented membrane demonstrated dramatic improvements in both permeance and selectivity in the separation of p-/o-xylene vapors. Yoon et al prepared highly c-oriented, fluorophore-containing LTL-type zeolite monolayers by inducing welldefined molecular linkages between LTL microcrystals and the substrates, and anisotropic photoluminescence was observed in the subsequent experiment [15].…”

Study of Anisotropic Photoluminescence and Energy Transfer in Oriented Dye-incorporating Zeolite-L Monolayer

“…7 A similar approach is also possible by enclosing fluorescence molecules inside a porous material and by choosing conditions such that the cavities are able to accommodate only monomers but not aggregates. [8][9][10][11] Among the porous materials, zeolite is known the suitable hosts for specific organization of chromophores, which is inorganic crystalline aluminosilicates with pores in nanometer size, because of their well-defined internal structure with uniform cages, cavities or channels. The aluminosilicate framework of the zeolite comprises a channel system of molecular dimensions (typically 0.4 -0.8 nm) providing a host matrix for adsorbent molecules.…”

“…The largest free diameter is about 12.6 Å, depending on the charge compensating cations. 8,9 With this background in mind, we have explored the methods of organizing zeolite microcrystals to film in the form of closely packed monolayers on various substrates as a host matrix for adsorbent molecules. [13][14][15][16] Based on our previous study about the monolayer assembly of zeolites on glass by the sonication assisted methods, 15 we could quickly prepare a uniaxially oriented zeolite monolayer film with a closed packing.…”

“…PyB + ions are of appropriate size for being inserted into the channels of zeolite-L. Since the length of PyB + ion (16.3 Å) is longer than the width of the zeolite-L lobe (12.6 Å), 9 the incorporated PyB + ions are forced to be lined up along the direction of channel. We also show that surface silylation of a host-guest nanocomposite is a very simple yet highly effective method for anisotropic fluorescence with highly dichroic ratio.…”