Research

Zeolite

Dye loaded zeolite L crystals can be assembled by using the advantages of the nitroxide exchange process. The reactions are reversible and the assembly can be conducted under mild conditions (Figure 1). [1]

 

Figure 1. A. Nitroxide exchange reaction of alkoxyamine-functionalized zeolite L crystals (green zeolites) with nitroxide-modified crystals (red zeolites) to form ordered zeolite chains. B. Self-assembly of zeolites L by nitroxide exchange process. Addition of excess TEMPO at room temperature led to disassembly.

Zeolites also can be assembled with living systems. Functionalized zeolite L crystals are non-covalently bound to nonpathogenic bacteria (Escherichia coli).  This assembly is formed by electrostatic interactions between the negatively charged outer cell membrane and the positively charged zeolite L crystal (Figure 2). The organism is able to “swim” in the solution even with a heavy load such as the 1-µm zeolite. [2]

 

 

Figure 2. A. 1:1 zeolite L/bacterium assembly in PBS buffer solution. B. Self-assembly of two bacteria with functionalized 1-µm zeolite L as the junction.

Zeolites can be assembled on conductive substrates without any chemical modification. By means of the microcontact printing technique (MCP), well-ordered and uniformly oriented zeolite L monolayers have been obtained on ITO (Figure 3), [3] which is a common substrate used for device fabrication and, therefore, open the way for further applications in optoelectronics.

 

Figure 3. Schematic representation of the strategy developed for transferring and patterning zeolite monolayers by mean of MCP technique.

 

Reference:

[1] B. Schulte, M. Tsotsalas, M. Becker, A. Studer, L. De Cola, Angew. Chem. Int. Ed., 2010, 49, 6881.

[2] Z. Popovic´, M. Otter, G. Calzaferri, L. De Cola,  Angew. Chem. Int. Ed. 2007, 46, 6188.

[3] F. Cucinotta, Z. Popovi?, E. A. Weiss, G. M. Whitesides, L. De Cola, Adv. Mater. 2009, 21, 1142.